Keston Combi 35Kw Users Manual

keston combi manual keston combi manual

2015-05-15

: Keston Keston-Combi-35Kw-Users-Manual-719673 keston-combi-35kw-users-manual-719673 keston pdf

Open the PDF directly: View PDF .
Page Count: 72

Download
Open PDF In Browser	View PDF

Combi 30 & 35
Installation and Servicing Instructions
FAN POWERED HIGH EFFICIENCY
MODULATING DOMESTIC CONDENSING
GAS COMBINATION BOILER
CE/PI No. 86-CL-38
Combi 30 - GC No. 47-930-04
Combi 35 - GC No. 47-930-05

These instructions must be left either with the
user or next to the site gas meter.
Keston Heating
PO Box 103, National Avenue, Kingston Upon Hull, HU5 4JN
Tel. +44 (0) 1482 443005 Fax. +44 (0) 1482 467133
email : info@keston.co.uk web : www.keston.co.uk
COMPLIANT WITH BUILDING REGULATION PART L1 & L2
SEDBUK A RATED

Keston Combi - Installation and Servicing

Notes for the installer
For any technical queries pleAse ring the KESTON
installer/technical helpline : 01482 443005
NOTE. BOILER RESET PROCEDURE To reset boiler, turn mode knob to reset position and immediately turn knob back to required setting.
The boiler will repeat the ignition sequence if a heat demand is present.

DOCUMENT amendments
Relevant Installation changes implemented in this book from Mod Level...... A02 (Oct 12) and A03 (Feb 14)
Page 11
Water Treatment - Addition of Adey Professional Heating Solutions
Page 31
Item “3” added to Electrical Installation
Statement added ref to commissioning process of combustion
Page 67
New Page Added - Benchmark Commissiong & Servicing Section
Page 68 & 69
New updated Commissioning Checklist & Service Record Sheets
Page 70 & 71
New pages added, Flowchart for CO Level and Combustion Ratio Check on Commissioning a Condensing Boiler

Keston reserve the right to vary specification without notice

Keston Combi - Installation and Servicing

general

Table 1 - General Data
Keston Combi

Gas supply

2H - G20 - 20mbar

Gas Supply Connection

15mm copper compression

Injector Size

(mm)

Inlet Connection

DHW

15mm copper compression

Outlet Connection

DHW

15mm copper compression

22mm copper compression

Flow Connection
Return Connection
Flue Terminal Diameter

4.65

4.9

mm (in)

Average Flue Temp-Mass Flow Rate

50 (nominal)
68 C - 13g/s

(DHW)

Maximum Working Pressure (Sealed Systems)

bar (lb/in2)

Maximum Domestic Hot Water Inlet Pressure

bar (lb/in2)

Minimum Domestic Hot Water Inlet Pressure*

bar (lb/in2)

73ºC - 15g/s

2.5 (36.3)
10.0 (145)
1.3 (18.9)

1.3 (18.9)**

Electrical Supply

230 V ~ 50 Hz.

Power Consumption

152

Fuse Rating

177

External : 3A

Water content

Internal : T4H HRC L250 V

litre (gal)

1.2 (0.26)

DHW

litre (gal)

0.5 (0.11)

Packaged Weight

kg (lb)

37.8 (83.3)

38 (83.8)

Maximum Installation Weight

kg (lb)

32.8 (72.3)

33 (72.8)

Boiler Casing Size

Height

mm (in)

700 (27.5)

Width

mm (in)

395 (15.5)

Depth

mm (in)

278 (11)

*Required for maximum flow rate. Boiler operates down to 2 l/min DHW delivery
** In areas of low water pressure the DHW restrictor can be removed
Table 2 - Performance Data - Central Heating
Max.

Boiler Input :
Boiler Input ‘Q’

Nett CV

kW
(Btu/h)

Gross CV

kW
(Btu/h)

Gas Consumption

Min. 30

Table 3 - Performance Data - Domestic Hot Water
Maximum DHW Input :

Min. 35

24.3

6.1

7.1

(82,900)

(20,700)

(24,100)

27.0

6.7

7.9

Nett CV

(Btu/h)
Gross CV

(92,000)

(23,000)

(26,900)

2.512

0.623

0.734

(ft3/h)

(89)

(22)

(25.9)

Gas Consumption

DHW Output
kW
(Btu/h)

Condensing

40 C Mean Water temp.
o

(Btu/h)

Seasonal efficiency*

NOx Classification

DHW Flow Rate

24.2

6.1

7.1

(20,700)

(24,100)

at 35°C temp. rise.

25.6

6.4

7.5

DHW Specific Rate

(87,400)

(21,800)

(25,500)

SEDBUK 2005

91.1%

91%

SEDBUK 2009

89%

88.9%

35
35.4

(103,600)

(120,900)
39.3

(115,000)

(134,200)

m3/h

3.135

3.658

(ft3/h)

(111)

(129)

30.3

35.3

(103,300)

(120,500)

(Btu/h)

(82,600)

30
30.4

33.7

Maximum

Boiler Output :
Non Condensing

kW
(Btu/h)

m3/h

70oC Mean Water temp.

l/min

12.4

14.5

(gpm)

(2.8)

(3.2)

l/min

14.5

16.9

(gpm)

(3.2)

(3.7)

CLASS 5

* The value is used in the UK Government’s Standard Assessment Procedure (SAP) for energy rating of dwellings. The test data from
which it has been calculated have been certified by a notified body.
Note. Gas consumption is calculated using a
calorific value of 38.7 MJ/m3 (1038 Btu/ft3) gross
or 34.9 MJ/m3 (935 Btu/ft3) nett
To obtain the gas consumption at a different
calorific value:
a. For l/s
- divide the gross heat input
(kW) by the gross C.V. of the gas (MJ/m3)
b. For ft3/h - divide the gross heat input (Btu/h)
by the gross C.V. of the gas (Btu/ft3)

Key to symbols
PMS = Maximum operating pressure of water
C13 C53 =

I2H

A room sealed appliance designed for connection via ducts to
a horizontal terminal, which admits fresh air to the burner and
discharges the products of combustion to the outside. The fan is
up stream of the combustion chamber.

= An appliance designed for use on 2nd Family gas, Group H only.

c. For m3/h - multiply l/s by 3.6.

Keston Combi - Installation and Servicing

general

KESTON Combi 30 & 35
Natural Gas only

Boiler size G.C. Appliance No. PI No.

(Benchmark No.)
30
35

47-930-04
47-930-05

86 CL 38
86 CL 38

Contents
Benchmark Commissioning Checklist ...................... 66
Boiler Clearances .......................................................... 9
Boiler Exploded Diagram ............................................ 12
Condensate Drain ........................................... 8,22,23,39
Electrical Connections ................................................ 25
Electrical Supply ........................................................... 8
Fault Finding ........................................................... 57-63
Flue System ............................................................ 14-17
Gas Safety Regulations ................................................ 7
Gas Supply ..................................................................... 8
Installation ............................................................... 12-36
Pump ............................................................................ 50
Safe Handling ................................................................. 6
Servicing ................................................................. 37-56
Short List of Parts ....................................................... 64
Thermostatic Radiator Valves ...................................... 8
Water and Systems ........................................... 8, 10-11
Water Connections ...................................................... 24
Water Treatment ..........................................................11
Wiring Diagram ............................................................ 30

For GB, to comply with Building Regulations Part L1 (Part 6 in Scotland) the boiler should be fitted in accordance with the
manufacturer’s instructions. Self-certification that the boiler has been installed to comply with Building Regulations can be
demonstrated by completing and signing the Benchmark Commissioning Checklist.
Before installing this boiler, read the Code of Practice sheet at the rear of this book.

Benchmark Commissioning Checklist Details
Boiler

Page

Make and model.......................................................... 5

Appliance serial no. on data badge ........... Front Cover

SEDBUK No. %........................................................... 4
Controls

Time and temperature control to heating.................. 26

Time and temperature control to hot water .............. 26

Heating zone valves................................................. n/a
TRV’s.......................................................................... 8

Auto bypass................................................................ 8

Boiler interlock............................................................. 8
For ..................................................................... all boilers

Flushing to BS.7593.................................................. 11
Inhibitor..................................................................... 11
Central heating mode
Heat input....................................................to be calculated

Page

Burner operating pressure....................................... n/a

Central heating flow temp.............measure and record

Central heating return temp..........measure and record
For combination boilers only

Scale reducer............................................................ 11
Hot water mode

Heat input.............................................to be calculated

Max. operating burner pressure............................... n/a

Max. operating water pressure......... measure & record

Cold water inlet temp....................... measure & record

Hot water outlet temp....................... measure & record

Water flow rate at max. setting......... measure & record
For condensing boilers only

Condensate drain...................................................... 22
For all boilers: complete, sign & hand over to customer
For assistance see Technical Helpline on the back page

NOTE TO THE INSTALLER: COMPLETE
THE BENCHMARK COMMISSIONING
CHECKLIST AND LEAVE THESE
INSTRUCTIONS WITH APPLIANCE

Keston Combi - Installation and Servicing

general
INTRODUCTION

Safe Handling

The Keston Combi boiler is a wall mounted, full sequence,
automatic spark ignition, low water content, fanned flue, high
efficiency, condensing, combination gas boiler.

This boiler may require 2 or more operatives to move it to its
installation site, remove it from its packaging base and during
movement into its installation location. Manoeuvring the boiler
may include the use of a sack truck and involve lifting, pushing and
pulling.

Note. Due to the high efficiency of the boiler a plume of water
vapour will form at the terminal during operation.
Central heating (CH) output is fully modulating with a range of:
30

6.1 to 24.2kW (20,700 to 82,600 Btu/h)

7.1 to 24.2kW (24,100 to 82,600 Btu/h)

Instantaneous domestic hot water (DHW) output is also fully
modulating with a maximum of :
30

30.3kW (103,300 Btu/h)

35.3kW (120,500 Btu/h)

The boiler is supplied fully assembled with DHW plate heat
exchanger, diverter valve, circulating pump, pressure gauge,
safety valve and CH expansion vessel.
Variable CH and DHW temperature controls are fitted on the user
control and the boiler features a DHW preheat facility.
The boiler includes as standard:
-
Automatic bypass
-
Boiler frost protection
-
Daily pump and diverter valve exercise.
-
Weather Compensation Kit

Caution should be exercised during these operations.
Operatives should be knowledgeable in handling techniques when
performing these tasks and the following precautions should be
considered:
• Grip the boiler at the base.
• Be physically capable.
• Use personal protective equipment as appropriate, e.g. gloves,
safety footwear.
During all manoeuvres and handling actions, every attempt should
be made to ensure the following unless unavoidable and/or the
weight is light.
•
•
•
•
•
•
•

Keep back straight.
Avoid twisting at the waist.
Avoid upper body/top heavy bending.
Always grip with the palm of the hand.
Use designated hand holds.
Keep load as close to the body as possible.
Always use assistance if required.

The boiler casing is of white painted mild steel.

Optional extra kits

The boiler temperature controls are visible located in the control
panel on the front of the boiler.

• Electronic Programmable Room Thermostat kit

The heat exchanger is manufactured from cast aluminium.
The boiler is suitable for connection to fully pumped, sealed
heating systems ONLY. Adequate arrangements for completely
draining the system by provision of drain cocks MUST be provided
in the installation pipework.

• Electronic Timer (7 day) kit
• Stand Off kit
• Air Terminal Finishing Kit
• Flue Sleeve Kit

Pipework from the boiler is routed downwards.

operation
With no demand for CH, the boiler fires only when DHW is drawn
off, or periodically for a few seconds without any DHW draw-off, in
order to maintain the DHW calorifier in a heated condition. This
only occurs if pre-heat knob is in the ‘ON’ period.
When there is a demand for CH, the heating system is supplied at
the selected temperature of between 45oC and 83oC, until DHW
is drawn off. The full output from the boiler is then directed via
the diverter valve to the plate heat exchanger to supply a nominal
DHW draw-off of:
30

12.4 l/min at 35 oC temperature rise.

14.5 l/min at 35 oC temperature rise.

When using the outside sensor provided please refer to page 27.
The DHW draw off rate specified above is the nominal that the
boiler flow regulator will give. Due to system variations and
seasonal temperature fluctuations DHW flow rates/temperature
rise will vary, requiring adjustment at the draw off tap.
At low DHW draw-off rate the maximum temperature is limited to
64 oC by the modulating gas control.
The boiler features a comprehensive diagnostic system which
gives detailed information on the boiler status when operating,
and performance of key components to aid commissioning and
fault finding.

Keston Combi - Installation and Servicing

general
Safety

Location of boiler

Current Gas Safety (installation and use) regulations or rules
in force:

The boiler must be installed on a flat and vertical internal wall,
capable of adequately supporting the weight of the boiler and any
ancillary equipment.

The appliance is suitable only for installation in GB and IE and
should be installed in accordance with the rules in force.
In GB, the installation must be carried out by a Gas Safe
Registered Engineer. It must be carried out in accordance with
the relevant requirements of the:
• Gas Safety (Installation and Use) Regulations

The boiler may be fitted on a combustible wall and insulation
between the wall and the boiler is not necessary, unless required
by the local authority.
For electrical safety reasons there must be no access available
from the back of the boiler.

• The appropriate Building Regulations either The Building
Regulations, The Building Regulations (Scotland), Building
Regulations (Northern Ireland).

The boiler must not be fitted outside.

• The Water Fittings Regulations or Water byelaws in Scotland.

If the boiler is to be fitted in a timber framed building it should be
fitted in accordance with the Institute of Gas Engineering document
IGE/UP/7:2006 Edition 2.

• The Current I.E.E. Wiring Regulations.
Where no specific instructions are given, reference should be
made to the relevant British Standard Code of Practice.
In IE, the installation must be carried out by a Registered Gas
Installer (RGII) and installed in accordance with the current edition
of I.S.813 “Domestic Gas Installations”, the current Building
Regulations and reference should be made to the current ETCI
rules for electrical installation.
Detailed recommendations are contained in the following British
Standard Codes of Practice:
BS. 5440:1 Flues (for gas appliances of rated input not
exceeding 70 kW).
BS. 5440:2 Ventilation (for gas appliances of rated input not
exceeding 70 kW).
BSEN. 12828:2003 Heating Systems in buildings: Design for
water based heating systems.

Timber Framed Buildings

Bathroom Installations
This appliance is rated IP20.
The boiler may be installed in any room or internal space, although
particular attention is drawn to the requirements of the current
IEE (BS.7671) Wiring Regulations and the electrical provisions
of the building regulations applicable in Scotland, with respect to
the installation of the boiler in a room or internal space containing
a bath or shower. For IE reference should be made to the current
ETCI rules for electrical installations and I.S. 813:2002.
If the appliance is to be installed in a room containing a bath or
shower then, providing water jets are not going to be used for
cleaning purposes (as in communal baths/showers), the appliance
must be installed beyond Zone 2, as detailed in BS.7671.

BSEN 12831:2003 Heating Systems in buildings: Method for
calculation of the design heat load.
BSEN 14336:2004

Heating Systems in buildings: Installation
and commissioning of water based heating
systems.

BS. 5546

Installation of gas hot water supplies for domestic
purposes (2nd Family Gases)

BS. 6798

Installation of gas fired hot water boilers of rated
input not exceeding 70 kW.

BS. 6891

Ceiling

Recessed
window
Zone 2

2.25m

Zone 1

0.6m

Low pressure installation pipes.

Health & Safety Document No. 635.

Zone 0

The Electricity at Work Regulations, 1989.

3G8913a

The manufacturer’s notes must NOT be taken, in any way, as
overriding statutory obligations.

Compartment Installations

IMPORTANT. These appliances are CE certificated for safety
and performance. It is, therefore, important that no external
control devices, e.g. flue dampers, economisers etc., are
directly connected to these appliances unless covered by
these Installation and Servicing Instructions or as otherwise
recommended by Keston in writing. If in doubt please enquire.

An existing cupboard or compartment may be used, provided that
it is modified for the purpose.

Any direct connection of a control device not approved by Keston
could invalidate the certification and the normal appliance
warranty. It could also infringe the Gas Safety Regulations and
the above regulations.

SAFE HANDLING OF SUBSTANCES
No asbestos, mercury or CFCs are included in any part of the
boiler or its manufacture.

A compartment used to enclose the boiler should be designed and
constructed specially for this purpose.

In both cases, details of essential features of cupboard /
compartment design, including airing cupboard installation, are to
conform to the following:
• BS 6798 (No cupboard ventilation is required - see ‘Air Supply’
for details).
• The position selected for installation MUST allow adequate
space for servicing in front of the boiler.
• For the minimum clearances required for safety and
subsequent service, see the wall mounting template and
Frame 1. In addition, sufficient space may be required to
allow lifting access to the wall mounting plate.
• The boiler must be installed on a fire resistant surface.

Keston Combi - Installation and Servicing

general
GAS SUPPLY

Water circulation system

The local gas supplier should be consulted, at the installation
planning stage, in order to establish the availability of an adequate
supply of gas. An existing service pipe must NOT be used without
prior consultation with the local gas supplier.

Important.

The boiler MUST be installed on a gas supply with a governed
meter only.

The central heating system should be in accordance with BS.6798
and, in addition, for smallbore and microbore systems, BS.5449.

A gas meter can only be connected by the local gas supplier or
by a Gas Safe Registered Engineer. In IE by a Registered Gas
Installer (RGII).

Water treatment - see Frame 5

Boiler Control Interlocks

An existing meter should be checked, preferably by the gas
supplier, to ensure that the meter is adequate to deal with the rate
of gas supply required.

Central heating systems controls should be installed to ensure
the boiler is switched off when there is no demand for heating, in
compliance with Building Regulations.

It is the responsibility of the Gas Installer to size the gas
installation pipework in accordance with BS6891:2005. Whilst the
principle of the 1:1 gas valve ensures the Keston Combi range
is able to deliver its full output at inlet pressures as low as 14mb,
other gas appliances in the property may not be as tolerant.
When operating pressures are found to be below the minimum
meter outlet of 19mb these should be checked to ensure this is
adequate for correct and safe operation.

Heating systems utilising full thermostatic radiator valve control
of temperature in individual rooms should also be fitted with a
room thermostat controlling the temperature in a space served by
radiators not fitted with such a valve.

Allowing for the acceptable pressure loss of 1mb across the
installation pipework, it can be assumed that a minimum permitted
operating pressure of 18mb will be delivered to the inlet of
the appliance. (Reference BS 6400-1 Clause 6.2 Pressure
Absorption).
The external gas cock could further reduce the operating pressure
when measured at its test point. The pressure drop is relative to
the heat input to the boiler (kW), refer to graph below.

A minimum length of 1 metre of copper pipe MUST be fitted
to both flow and return connections from the boiler before
connection to any plastic piping.

When thermostatic radiator valves are used, the space heating
temperature control over a living / dining area or hallway having
a heating requirement of at least 10% of the minimum boiler heat
output should be achieved using a room thermostat, whilst other
rooms are individually controlled by thermostatic radiator valves.
However, if the system employs thermostatic radiator valves on all
radiators, or two port valves, then a bypass circuit must be fitted
with an automatic bypass valve to ensure a flow of water should
all valves be in the closed position.

Electrical supply
Warning.
This appliance must be earthed.
Wiring external to the appliance MUST be in accordance with
the current I.E.E. (BS.7671) Wiring Regulations and any local
regulations which apply. For IE reference should be made to the
current ETCI rules for electrical installations.
The mains supply to the boiler and system wiring centre shall
be through one common fused double pole isolator and for
new heating systems, and where practical replacement boiler
installations, the isolator shall be situated adjacent to the
appliance.

Condensate drain
Refer to Frames 20 & 21
Important.

Installation pipes must be fitted in accordance with BS.6891. In IE
refer to IS.813:2002.
The complete installation MUST be tested for gas tightness and
purged as described in the above code.

A condensate drain is provided on the boiler. This drain must be
connected to a drainage point on site. All pipework and fittings in
the condensate drainage system MUST be made of plastic - no
other materials may be used.

Important.
Any external runs must be in accordance with BS 6798.
The drain outlet on the boiler is sized for standard 21.5mm (3/4”)
overflow pipe. It is a universal fitting to allow use of different
brands of pipework.

Keston Combi - Installation and Servicing

general
1 boiler dimensions, services & clearances

all dimensions in mm

The boiler connections are made on the boiler connection tails.
Refer to Frame 22.
The following minimum clearances must be maintained for
operation and servicing.
Additional space will be required for installation, depending upon
site conditions.

2.5
from case

2.5

30mm
Minimum Top Clearance

395
62

198
155

89
Air

Flue

700

100 *

395

400

Gas Inlet

Front clearance
The minimum front clearance when built in to a cupboard is 5mm
from the cupboard door but 450mm overall clearance is still
required, with the cupboard door open, to allow for servicing.

* Bottom clearance

Bottom clearance after installation can be reduced to 5mm.
This must be obtained with an easily removable panel, to enable
the consumer to view the system pressure gauge, and to provide
the 100mm clearance required for servicing.

Keston Combi - Installation and Servicing

general
2

system requirements - Central Heating

Notes
a. The method of filling, refilling, topping up or flushing sealed
primary hot water circuits from the mains via a temporary
hose connection is only allowed if acceptable to the local
water authority.

Safety valve setting

bar

3.0

Vessel charge pressure

bar

0.5 to 0.75

System pre-charge pressure bar
System volume
(litres)

b. Antifreeze fluid, corrosion and scale inhibitor fluids suitable
for use with boilers having aluminium heat exchangers may
be used in the central heating system.

General
1. The installation must comply with all relevant national and local
regulations.
2. The installation should be designed to work with flow
temperatures of up to 86 oC.
3. All components of the system must be suitable for a working
pressure of 3 bar and temperature of 110 oC. Extra care should
be taken in making all connections so that the risk of leakage is
minimised.

The following components are incorporated within the appliance:

a. Circulating pump.

b. Safety valve, with a non-adjustable preset lift pressure of 3
bar.

c. Pressure gauge, covering a range of 0 to 4 bar.

d. An 8-litre expansion vessel, with an initial charge pressure
of 0.75 bar.

None

1.0

Expansion vessel
volume (litres)

1.6

1.8

3.1

3.7

4.7

5.5

100

6.3

7.4

125

7.8

9.2

150

9.4

11.0

175

10.9

12.9

190

11.9

14.0

200

12.5

14.7

250

15.6

18.4

300

18.8

22.1

0.063

0.074

For other system volumes
multiply by the factor access
Water Flow Rate and Pressure Loss
Max CH Output

kW
(Btu/h)

Water flow rate
Temperature Differential

l/min

17.3

(gal/min)

(3.8)

( F)
o

Head available for
system

24.2
(82,600)

20
(36)

m.w.g.

3.4

(ft.w.g.)

(11.1)

4. ‘Make-up’ Water. Provision must be made for replacing water
loss from the system, either :
a. From a manually filled ‘make-up’ vessel with a readily visible 5. Filling
water level. The vessel should be mounted at least 150mm
The system may be filled by the following method:
above the highest point of the system and be connected
through a non-return valve to the system, fitted at least Where the mains pressure is excessive a pressure
150mm below the ‘make-up’ vessel on the return side of
reducing valve must be used to facilitate filling.
the radiators. or
a. Thoroughly flush out the whole system with cold
b. Where access to a ‘make-up’ vessel would be difficult, by
water.
pre-pressurisation of the system.
b.
Fill and vent the system until the pressure gauge

The maximum cold water capacity of the system should
registers 1bar and examine for leaks. Refer to Frame
not exceed 143 litres, if not pressurized. However, if
22 for filling detail.
the system is to be pressurized, the efficiency of the
c.
Check the operation of the safety valve by raising the
expansion vessel will be reduced and a larger vessel
water pressure until the valve lifts. This should occur
(or smaller system volume) may be necessary. If the
within 0.3bar of the preset lift pressure.
capacity of the vessel is not considered sufficient for this,
or for any other reason, an additional vessel must be
d. Release water from the system until the
installed on the RETURN to the boiler.
minimum system design pressure is reached;
1.0 bar if the system is to be pre-pressurised.

Guidance on vessel sizing is given in Table above.

continued . . . . . .

Keston Combi - Installation and Servicing

general
3

system requirements cont’d

Domestic Hot Water
1. The domestic hot water service must be in accordance with
BS 5546 and BS 6700.
2. Refer to Table 1 for minimum and maximum working
pressures. In areas of low mains water pressures the
domestic hot water regulator may be removed from the DHW
flow turbine cartridge. Refer to Frame 70. The boiler will
require the flow rate to be set to obtain a temperature rise of
35oC at the tap furthest from the boiler.
3. The boiler is suitable for connection to most types of washing
machine and dishwasher appliances.
4. When connecting to suitable showers, ensure that:

a. The cold inlet to the boiler is fitted with an approved antivacuum or syphon non-return valve.

b. Hot and cold water supplies to the shower are of equal
pressure.

5. Hard Water Areas
Where the water hardness exceeds 200mg/litre, it is
recommended that a proprietary scale reducing device is
fitted into the boiler cold supply within the requirements of the
local water company.

Important
Provision must be made to accommodate the expansion of DHW
contained within the appliance, if a non-return valve is fitted to the
DHW inlet, or a water meter with a non-return valve is installed.
Cold water rising main and pipework in exposed areas need to
be suitably lagged to prevent freezing.

5 water treatment
Central Heating
The Keston Combi range boiler has an aluminium alloy
heat exchanger.
Important.
The application of any other treatment to this product
may render the guarantee of Keston Invalid.
Keston recommend Water Treatment in accordance with the
Benchmark Guidance Notes on Water Treatment in Central
Heating Systems.
If water treatment is used Keston recommend only the use
of SCALEMASTER GOLD 100, Fernox, MBI, Adey MC1 or
Sentinel X100 inhibitors and associated water treatment
products, which must be used in accordance with the
manufacturers’ instructions.
Notes.
1. It is most important that the correct concentration of the
water treatment products is maintained in accordance
with the manufacturers’ instructions.
2. If the boiler is installed in an existing system any
unsuitable additives MUST be removed by thorough
cleansing. BS 7593:2006 details the steps necessary to
clean a domestic heating system.
3. In hard water areas, treatment to prevent lime scale may
be necessary - however the use of artificially softened
water is NOT permitted.
4. Under no circumstances should the boiler be fired
before the system has been thoroughly flushed.

Keston Combi - Installation and Servicing

system balancing

The boiler does not normally need a bypass but at least
some radiators on the heating circuit, of load of at least
10% of the minimum boiler output, must be provided with
twin lockshield valves so that this minimum heating load
is always available. See note regarding thermostatic
radiator valves on page 8.
Note. Systems incorporating zone valves which could
completely cut off the flow through the system must also
include a bypass.

Balancing
1. Set the programmer to ON.

Close the manual or thermostatic valves on all
radiators, leaving the twin lockshield valves (on the
radiators referred to above) in the open position.

Turn up the room thermostat and adjust the
lockshield valve to give an uninterrupted flow through
the radiator.

These valves should now be left as set.

2. Open all manual or thermostatic radiator valves
and adjust the lockshield valves on the remaining
radiators, to give around 20oC temperature drop at
each radiator.
3. Adjust the room thermostat and programmer to
normal settings.

Domestic Hot water
In hard water areas where mains water can exceed 200ppm
Total Hardness (as defined by BS 7593:2006 Table 2) a scale
reducing device should be fitted into the boiler cold supply within
the requirements of the local water company. The use of artificially
softened water, however, is not permitted.
Keston recommend the use of Fernox Quantomat, Sentinel
Combiguard or Calmag CalPhos I scale reducing devices together
with scalemaster in-line scale inhibitor branded Ideal, which must
be used in accordance with the manufacturers’ instructions.
For further information contact:
Fernox Cookson Electronics
Forsyth Road, Sheerwater, Woking, Surrey GU21 5RZ
+44 (0) 870 601 500
Sentinel Performance Solutions
The Heath Business & Technical Park, Runcorn, Cheshire WA7 4QX
Tel: 0800 389 4670
www.sentinel-solutions.net
Scalemaster Water Treatment Products
Emerald Way, Stone, Staffordshire ST15 0SR
Tel: +44 (0) 1785 811636
Calmag Ltd.
Unit 3-6, Crown Works, Bradford Road, Sandbeds, Keighley,
West Yorkshire BD20 5LN
Tel: +44 (0) 1535 210 320
Adey Professional Heating Solutions
Gloucester Road, Cheltenham GL51 8NR
Tel: +44 (0) 1242 546700

INSTALLATION

INSTALLATION
6 boiler assembly - exploded view
104
105
106
107
108
110
111
112
113
114
115
116
117
118
119

120 Flow Group Manifold
121 Plate Heat Exchanger
127 Flow Sensor Hall Effect
128 Flow Turbine Cartridge
131 Water Pressure Transducer
135 Pressure Gauge
136 Safety Valve Drain Pipe
203 Gas Cock
204 Pipe - Gas Inlet
205 Gas Valve
206 Pipe - Gas Injector
211 Injector Assembly
214 Venturi
215 Fan
217 Burner

CH Return Valve
CH Flow Valve
DHW Inlet & Outlet
Filling Loop
Pump Head
Air Vent Pump
Diverter Valve Head
Diverter Valve Cartdrige
Pressure Relief Valve
Pipe - PRV Outlet
Pipe - Flow
Pipe - Return
Pipe - Expansion Vessel
Expansion Vessel
Return Group Manifold

218
219
223
224
227
228
229
231
301
302
303
304
306
307
308

309
313
314
324
325
326
332
401
503
504
505
506
507
136
512
332

Gasket - Burner
Sump Clean Out Cover
Flue Manifold
Flue Manifold Top
Clamp Retaining Flue Turret
Hose Condensate Internal
Siphon Trap
Condensate Outlet Connection
Ctrs Box Fixings Hinge & Spring
Primary PCB*
CUI Board
Control Thermistor (Return)
Electrode Ignition
Electrode Detection
Igniter Unit

Thermistor No Flow
Ignition Lead
Control Box Lens
Controls Box Lid
Control Box Front
Programmer Insert
Flue Thermostat
Heat Engine
Wall Mounting Bracket
Front Panel
Fascia
Bracket - Gas Valve
Bracket - Exp. Vessel
Safety Valve Drain Pipe
Drop Down Door
Flue Thermostat

* Note that production boiler PCBs are
factory pre-set to operate for boiler range
and output. When ordering Primary PCB
as a spare, an additional Boiler Chip Card
(BCC) MUST also be purchased for your
specific boiler range and output.

227
504

Check boiler serial letter code on data
plate to obtain correct BCC.

224
505

503

512

313
218

217
215

507

309
306

211

214

206

118

401

308

307

121
120

506
116 301

115

128

136

127
228 112

205
219 304

113
119

229

204

111

231

114

303

108
105

223

131

110

106

332

203

106

117

104

324
135

314
326

325

302

107
*

Keston Combi - Installation and Servicing

INSTALLATION
unpacking

INSTALLATION

Unpack and check the contents.
Pack 1 Contents

A Boiler
B

Hardware Pack Box

Wall Mounting Plate

D
E

These Installation Instructions
Wall Mounting Template
(located on internal protective packaging)

Turret Clamp

C
H
Boiler Guarantee

G Safety Valve Drain Pipe
H

Boiler Guarantee / Registration pack

HARDWARE PACK CONTENTS
Gas Valve Pack

Gas Valve Pack
1. Pipe - Gas Inlet
2. Washer - Gas (blue)
3. Gas Cock

DHW Pack
2

3
1

Filling Loop Pack
1. 3/8" Fibre washer (x4)
2. Valve (double check valve) fitting
3. Valve - Filling Loop
4. Plastic Chain (x2)
5. Filling Loop
6. 3/8" Blanking Rubber Washer (x2)

Filling Loop

4
3

Return Valve Pack
1. Pipe CH Return
2. Washer CH
3. Valve Return

3
5

Accessory Pack

DHW Pack
1. Pipe DHW Outlet
2. Valve - Return DHW
3. Washer DHW (x2)
4. Pipe DHW Inlet
5. Nut 1/2"

1
2

Return Valve Pack
3

Accessory Pack
1. Screw (x2)
2. Wallplug (x2)
3. Turret Clamp Screw (x1)

Flow Valve Pack

1
2

Flow Valve Pack
1. Pipe CH Flow
2. Washer CH
3. Valve Flow (with gauge)

Flue Pack Contents
A
B
C
D
E
F
G
H
J

Flue Adaptor
Air Spigot
Terminals - 2 off
Flue Sleeve
Wall Plate
Wall Seal
Outside Sensor
Screws - 4 off
Wall Plugs - 4 off

E
D

continued . . . . .

Keston Combi - Installation and Servicing

INSTALLATION
8

FLUE SYSTEM

IMPORTANT
When installing a replacement boiler a new flue system must be used. DO NOT re-use the existing boiler
flue installation.

Design
Individual air supply and flue outlet pipes are used as standard.

The material approved for this application is which MUST be used is:
Marley muPVC Solvent Weld System (50mm) and Polypipe System 2000 muPVC solvent weld
(50mm), to BS5255 and/or BSEN1566-11 and BSEN1329, are the only systems approved for this
application.
The following pipe and fittings are approved.

Polypipe System 2000 muPVC solvent Weld System (50mm)

Poly Pipe Code
MU 301

4m length muPVC wastepipe 5/225

MU 313

50mm x 45 deg muPVC obtuse bend

MU 314

50mm x 92.5 deg muPVC swept bend

MU 310

50mm muPVC straigh coupling

MU 316

50mm x 92.5 deg muPVC swept pipe

Marley muPVC Solvent Weld System (50mm)

FLUE OUTLET

Marley Code
KP 304

50mm x 4m double spigot pipe

KP32

50mm x 45 deg bend

KSC3

50mm straight coupling

KB3

50mm x 88.5 deg bend

KT3

50mm swept tee

Consideration MUST be given to expansion and contraction of the flue. Refer to Assembly Practice Frame in this installation and
Servicing Instructions for further guidance.

continued............

Keston Combi - Installation and Servicing

INSTALLATION
9

FLUE SYSTEM.... CONT’D

Termination of the flue and air
The flue and air pipes may terminate independently through any
external walls within the same dwelling except on opposing walls,
within the maximum lengths shown in graph below.
The air pipe must have an elbow and 150mm length of pipe
directed downwards with a termination grill fitted.

TERMINAL POSITIONS

Flue
Pipe

Minimum Separation
140mm

Elbow

The air pipe can be situated at the side or beneath the flue pipe to
a minimum dimension of 140mm (see diagram below). It must not
be sited above the flue pipe.

Condensing boiler emit a visible plume of water vapour from the
flue terminal, this is normal. It is the responsibility of the installer
to judiciously select a terminal location that does not cause a
nuisance.
If either the flue or air terminal is below a height of 2m from ground
level a terminal guard must be fitted.

Acceptable
range of air
pipe siting

150mm

The flue and air pipes must extend by at least 40mm from the wall
surface.

Air Pipe
Terminal

Maximum lengths

Slope
‘Horizontal’ flue outlet pipework MUST slope at least 1.5 degrees (26mm per metre run) downwards towards the boiler. Pipework
can be vertical. Only swept elbows can be used.
Air inlet pipework can be truly horizontal or vertical, or sloping in a downward direction towards the boiler but in each case rain, etc.,
must be prevented from entering the pipe. There must be no troughs in any of the pipework, whether it be air inlet or flue
outlet.

Keston Combi - Installation and Servicing

FLUE OUTLET

Due to the resistance presented by extended flue length a slight reduction in maximum boiler output will occur where
combined flue and air lengths in excess of 18.0m and 16.0m (50mm muPVC) are used. In such cases the boiler output will be
reduced by 0.6% and 0.8% per additional metre.
The maximum lengths of both air inlet pipe and flue outlet pipe, when no bends are used, are as detailed in graphs below.
However, each bend used has an equivalent length that must be deducted from the maximum straight length stated in graphs
below. Knuckle bends must not be fitted.
A 92.5º swept elbow is equivalent to 1.0m straight length. A 45º bend is equivalent to 0.5m straight length.
It is possible to have variable flue and air lengths as described within the shaded area of graphs below.

INSTALLATION
10 Flue Installation Example Keston Combi 30
4m
1.5º back
to boiler

Keston Combi 30 - Flue & Air Pipe Length

Sleeve

15.5

Air Pipe Length [m]

30
Bracket at
each 1 metre
6m
2m 1.5m

0.15m

26
22
18
14
10.15

6
1.5º back
to boiler

Acceptable Operating Area
2

10 12 14 16 18 20 22 24 26 28 30

Flue Pipe Length [m]
Calculations
Air
Elbows 2 x 1m = 2m
Straights 6+2+0.15 = 8.15m
Total = 10.15m

Flue
Elbows 3 x 1m = 3m
Straights 4+6+1.5+1 = 12.5m
Total = 15.5m

Overall Flue / Air = 25.65m

Keston Combi 35 - Flue & Air Pipe Length

14.5

26
Sleeve

Air Pipe Length [m]

FLUE OUTLET

11 Flue Installation Example Keston Combi 35

Air
0.15m

4m
1.5º back
to boiler

3.5m

1.5m

2m
Bracket every
1 metre
1.5º back
to boiler

22
18
15.65

14
10
6

Air
4 x 90º elbows
Straight lengths

2.5m

Calculations
Flue
4
3 x 90º elbows
2
Straight lengths
2
3.5
4
0.15
15.65

Acceptable Operating Area
2

10 12 14 16 18 20 22 24 26 28
Flue Pipe Length [m]

3
2.5
1.5
3.5
4
14.5

Overall Flue / Air = 30.15m

Keston Combi - Installation and Servicing

INSTALLATION
12 Flue Termination Position
Twin Flue Positions

Flue Minimum Spacing

Air Minimum Spacing

A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
M.
N.

Below an opening (1)
Above an opening (1)
Horizontally to an opening (1)
Below gutters, soil pipes or drain pipes
Below eves
Below balcony or car port roof
From a vertical drain pipe or soil pipe
From an internal or external corner or to a boundary alongside the terminal
Above ground, roof or balcony level
From a surface or a boundary facing the terminal
From a terminal facing the terminal
From an opening in the car port into the building
Vertically from a terminal on the same wall
Horizontally from a terminal on the same wall

(1)

An opening here means an openable element, such as a openable window, or a fixed opening such as an air vent. However, in addition, the outlet should not
be nearer than 150mm (fanned draught) to an opening into the building fabric formed for the purpose of accommodating a built in element, such as a window frame.

300 mm
300 mm
300 mm
75 mm
200 mm
200 mm
150 mm
300 mm
300 mm
600 mm
1200 mm
1200 mm
1500 mm
300 mm

12"
12"
12"
3"
8"
8"
6"
12"
12"
24"
48"
48"
60"
12"

50 mm
50 mm
50 mm
75 mm
50 mm
50 mm
50 mm
50 mm
100 mm
100 mm
1200 mm
100 mm
1500 mm
300 mm

2"
2"
2"
3"
2"
2"
2"
2"
4"
4"
48"
4"
60"
12"

The dimensions given in the table above may need to be increased to avoid wall staining and nuisance depending on site conditions.

boundary
D, E

I
B
J

A
L

M
H

boundary

FLUE OUTLET

General Installations
All parts of the system must be constructed in accordance with BS 5440 Part 1, except where specifically mentioned in these
instructions.
All pipe work must be adequately supported.
All joints other than approved push-on or plastic compression connectors must be made and sealed with solvent cement suitable
for muPVC pipes and conforming to BS 6209: 1982.
Consideration must be given to Corgi/Gas Safe bulletin TB200/TB008 regarding flues in voids.
The boiler casing must always be correctly fitted to the boiler when leaving the appliance operational.
External wall faces and any internal faces of cavity walls must be good.

Air Supply
The Keston Combi is a room-sealed appliance and therefore does not require purpose provided ventilation to the boiler room for
combustion air.

Compartment installation
Due to the low casing temperatures generated by the boiler, no compartment ventilation is required. However, the cupboard or
compartment must not be used for storage.

Keston Combi - Installation and Servicing

13 INSTALLING the boiler
Installation of the boiler is straightforward but consideration must be given to access to allow flue and air pipes to be pushed
through walls and ceilings. The order in which the components are installed will depend upon particular site conditions, but in
general it will be easiest and most accurate to install the boiler and then build up the flue outlet and air inlet pipes to the terminal
- this is the sequence described.

14 wall mounting template
The wall mounting template is located on the internal protective
packaging.
Note.
The template shows the positions of the fixing holes and
the position of the air and flue connections. Care MUST be
taken to ensure the correct holes are drilled.
1. Tape template into the selected position. Ensure squareness
by hanging a plumbline as shown.
2. Mark onto the wall the following:
a The wall mounting plate screw positions (choose one from
each group).

b The position of the air and flue when exiting straight out of
the wall where the boiler is mounted.

Note. Mark the centre of the hole as well as the
circumference.
3. Remove the template from the wall.

15 preparing the wall
Important.
Ensure that, during the cutting operation, masonry falling
outside of the building does not cause damage or personal
injury.
1. Cut the flue and air holes (preferably with 60mm core bore
tool) ensuring the holes are square to the wall.

Rear flue only
60mm diameter
holes

2. Drill 2 holes with a 7.5mm / 8mm masonry drill and insert
the plastic plugs, provided, for the wall mounting plate.
3. Locate 2 No.14 x 50mm screws in the wall mounting plate
(one at each side, in any of the 3 holes provided at each
side) and screw home.

X
Section
through wall
Note. Check all of the hole
positions before drilling.

3G10030

INSTALLATION

Keston Combi - Installation and Servicing

INSTALLATION

Screw the wall mounting plate to the wall using 2 wall plugs
(previously fitted) with the 2 screws provided.
Choose one of the 2 sets of slots in left and right bank.
Ensuring that at least one of the screws is fitted into a top slot.

17 Mounting the Boiler

INSTALLATION

16 Fitting the Wall Mounting Plate

1. Ensure the plastic plugs are removed from both the CH
and DHW connections before mounting the boiler.
2. Lift the boiler onto the wall mounting plate (refer to the
Introduction section for safe handling advice), locating it
over the two tabs.

Example of fixing

esp9496

Keston Combi - Installation and Servicing

INSTALLATION
18 assembly practice
Remove all plastic debris and burrs when installing air intake
piping. Plastic fillings caused by cutting muPVC pipe must not
be allowed to be drawn into the combustion air blower. Prevent
dust entering the air intake when cutting on building sites. Blower
failure which is determined to be caused by plastic filings or other
debris will not be covered by guarantee.

installing flue and air pipes
Important - When installing the boiler on an existing system a
new flue and air intake system MUST also be installed. You
MUST NOT re-use existing flue or air pipework components.
Using the same methods drill any further holes (always
covering existing pipework), cut and assemble the
pipework.

•

From outside, complete the two terminations - See Frame
8 Flue System and make good all holes. (Wall sealing
collars are available to make good hole areas on the wall
face (part number C.08.0.00.07.0).

•

Measure, cut and check the air and flue pipes to pass to the
exit from the wall(s) or ceiling.

Support any pipes whose route could be displaced
either of its own accord or by accident. Any horizontal
run over 1m or vertical runs of any length must
always be supported. Brackets should be placed at
intervals of approximately 1m. Brackets should be
loose enough on the pipe to allow thermal expansion
and contraction movement.

•

Always thoroughly deburr all pipes and most important,
remove shavings from within the pipe.

Flue pipework through walls MUST be sleeved to
allow thermal expansion and contraction movement.

•

Check all connections for security and re-seal any joints
using solvent cement where soundness may be in doubt.

Remove the flue adaptor and air spigot from the flue pack
supplied with the boiler.

•

Remove boiler front panel - Frame 39.

•

Remove air intake blanking plate by unscrewing 4 x M5
screws and put to one side, leaving sponge gasket in
place.

•

Fix air spigot to boiler using the 4 M5 screws, see diag.
below. Ensure sponge gasket is in place and not damaged.

•

Insert the flue adaptor into the flue manifold on the top of the
boiler and secure using the clamp provided in the packaging
box, see diagram below.

•
•

FLUE OUTLET

•

Assemble, using solvent weld cement, the pipework from
the boiler connections to the exit from the first wall/ceiling,
(remount the boiler if removed). When pushing pipe through
walls, ensure grit and dust is not allowed to enter the pipe.

Ensure pipes are fully engaged into sockets and solvent
welded with no leaks.

Note. It is equally important to seal the air inlet with solvent
cement as the flue outlet pipe joints.

Keston Combi - Installation and Servicing

INSTALLATION
19 Fitting the FLUE SleevE
1. Cut hole in wall.
2. Measure wall Thickness
3. Cut sleeve length to match wall thickness & remove burrs.
4. Grout sleeve into wall with flange on external face.
5. Slide flue pipe into sleeve, checking it is free to slide.
6. Slide Flexible wall seal over flue pipe and push centre ring up to sleeve flange when cold.
7. Locate wall plate over flexible wall seal and clamp in place using the raw plug pack.
8. Affix flue terminal
9. During boiler test check that the flue end is free to expand and contract with flexible wall seal.

Flue
Terminal

Flue Pipe

Flue Sleeve

Flue Sleeve Flange
Wall
Plate

FLUE OUTLET

Flexible
Wall
Seal

Keston Combi - Installation and Servicing

20 condensate drain

149

This appliance is fitted with a siphonic 75mm condensate trap

system that requires filling before operating the appliance for the
first time or after maintenance.
All condensate pipework should conform to the following:
a. Where a new or replacement boiler is being installed, access to
an internal ‘gravity discharge’ termination should be one of the
main factors considered in determining boiler location.
b. Plastic with push fit or solvent connections.
c. Internal plastic pipe work a minimum of 19mm ID (typically
22mm OD)
d. External plastic pipe must be a minimum of 30mm ID (typically
32 OD) before it passes through the sleeved wall.
e. All horizontal pipe runs, must fall a minimum of 45mm per metre
away from the Boiler.
f. External & unheated pipe work should be kept to a minimum
and insulated with Class “O” waterproof pipe insulation.
g. All installations must be carried out in accordance to the
relevant connection methods as shown in the “Condensate
installation diagrams” & BS6798:2009
h. Pipe work must be installed so that it does not allow spillage
into the dwelling in the event of a blockage (through freezing)
i. All internal burrs should be removed from the pipe work and any
fittings.
In order to minimise the risk of freezing during prolonged very cold
spells, one of the following methods of terminating condensate
drainage pipe should be adopted.
Internal Drain Connections
Wherever possible, the condensate drainage pipe should be routed
to drain by gravity to a suitable internal foul water discharge point
such as an internal soil and vent stack or kitchen or bathroom
waste pipe etc. See Figs 1 and 2.

Figure 1 - Connection of Condensate Drainage Pipe to
Internal Soil & Vent Stack

≥ 450
Boilers without 75mm sealed
condensate trap must be fitted with
a 75mm trap and visible air break

-
-

For connections to an external soil/vent stack see Fig 4.
Insulation measures as described should be used.
When a rainwater downpipe is used, an air break must be
installed between the condensate drainage pipe and the
downpipe to avoid reverse flow of rainwater into the boiler
should the downpipe become flooded or frozen, see Fig 5.
Where the condensate drain pipe terminates over an open
foul drain or gully, the pipe should terminate below the grating
level, but above water level, to minimise “wind chill” at the open
end. The use of a drain cover (as used to prevent blockage by
leaves) may offer further prevention from wind chill. See Fig 6.
Where the condensate drain pipe terminates in a purpose
designed soak away (see BS 6798) any above ground
condensate drain pipe sections should be run and insulated as
described above. See Fig 7

Unheated Internal Areas
Internal condensate drain pipes run in unheated areas, e.g. lofts
basements and garages, should be treated as external pipe.
Ensure the customer is aware of the effects created by a frozen
condensate and is shown where this information can be found in
the user manual.

Figure 2 - Connection of a Condensate Drainage Pipe
Downstream of a Sink, Basin, Bath or Shower Water Trap to
Internal Soil Vent Stack

≥ 100

Min Ø 19mm
Internal pipe

The external pipe run should be kept to a minimum using the most
direct and “most vertical” route possible to the discharge point, with
no horizontal sections in which condensate might collect.

Boiler
with 75mm
sealed
condensate
trap

Soil & vent stack

Boiler
with 75mm
sealed
condensate
trap

External Drain Connections
The use of an externally run condensate drainage pipe should
only be considered after exhausting all internal termination options
as described previously. An external system must terminate at a
suitable foul water discharge point or purpose designed soak away.
If an external system is chosen then the following measures must
be adopted:

Minimum
connection
height up to 3
storeys

Sink/basin/
bath or
shower

Min Ø 19mm
Internal pipe

Condensate
Drain

≥ 100

203

Condensate Pump
Where gravity discharge to an internal termination is not physically
possible or where very long internal pipe runs would be required
to reach a suitable discharge point, a condensate pump of a
specification recommended by the boiler or pump manufacturer
should be used terminating into a suitable internal foul water
discharge point such as an internal soil and vent stack or internal
kitchen or bathroom waste pipe etc. (fig 3).

Internal soil & vent stack

INSTALLATION

Boilers without 75mm sealed
condensate trap must be fitted with
a 75mm trap and visible air break

continued . . . . .

Keston Combi - Installation and Servicing

INSTALLATION

Boiler
with 75mm
sealed
condensate
trap

Min Ø 30mm
Internal pipe

Boiler
with 75mm
sealed
condensate
trap

Water/
weather proof
insulation

Min Ø 19mm
Internal pipe
Min Ø 30mm
Internal pipe

Boiler
with 75mm
sealed
condensate
trap
combined foul/
rain water drain
External air
break
Air gap

Terminated
and cut at 45º
43mm 90º male/
female bend

68mm Ø PVCU
Strap on fitting

Minimum
connection
height up to 3
storeys

Figure 6 - Connection of Condensate Drainage Pipe
Upstream of a Sink, Basin, Bath or Shower Waste Trap to
External Drain, Gulley or Ranwater Hopper

Visible air break
at plug hole

Min Ø 19mm
Internal pipe
Sink, basin, bath or
shower with integral
overflow and 75mm trap

Figure 5 - Connection of a Condensate Drainage Pipe to an
External Rainwater Downpipe (only combined foul/rainwater
drain)

Boilers without 75mm sealed
condensate trap must be fitted with
a 75mm trap and visible air break

≥ 100

Condensate pump
(Install in accordance with manufacturers instructions)

≥ 450

Min Ø 19mm
Internal pipe

Water/
weather proof
insulation

Minimum 30mm
internal pipe

45º pipe
termination

≥ 25 Below grate

Min Ø 19mm
Internal pipe

Water/weather
proof insulation

Visible air break

Boiler
with 75mm
sealed
condensate
trap

Figure 4 - Connection of condensate Drainage Pipe to
External Soil & Vent Stack

Soil & vent stack

Figure 3 - Connection of a Condensate Pump Typical
Method (see manufacturers detailed instructions)

INSTALLATION

21 Condensate drain - Cont’d.......

Figure 7 - Connection of a Condensate Drainage Pipe to an
External Purpose Made Soak Away.

Boiler
with 75mm
sealed
condensate
trap

Max 3m external
pipework

Boilers without 75mm sealed
condensate trap must be fitted with
a 75mm trap and visible air break

≥ 300

≥ 25

Min Ø 19mm
Internal pipe

Water/Weather
proof insulation

Min Ø 30mm
Internal pipe

≥ 500

Limestone
chippings

2 rows of three Ø12mm holes
25mm centres, 50mm from
the bottom of the tube, facing
away from the house

Keston Combi - Installation and Servicing

INSTALLATION

INSTALLATION
22 connections & Filling
NOTES.
Ensure all boss blanking plugs are removed before connecting hardware. Each
valve must be fitted to the correct boss as shown in the picture.

Note. The domestic hot water flow rate
is automatically regulated to a maximum
of 12.4 l/m (2.8 gpm)

Ensure each union is fitted with fibre seals provided.
Do not subject any of the isolating valves to heat as the seals may be damaged.

WATER CONNECTIONS CH

FILLING

1. Connect the CH flow service valve (black handle) and
copper tail provided in the hardware pack to the threaded
boss connection provided at the lower rear of the boiler.

FILLING

2. Connect the CH rtn. valve (black handle) and copper tail.
3. If connecting the boiler to heating loads in excess of
60,000 Btu/h, connecting flow and return heating systems
pipework must be sized in 28mm diameter at the point
of pipe connection to the boiler tails. use 22mm x 28mm
pipe adaptors as appropriate.

WATER CONNECTIONS DHW
1. Fit the DHW inlet service valve (blue handle) and copper tail
to the threaded boss connection ensuring the seal provided
is correctly located.
2. Fit the DHW outlet pipe tail to DHW outlet connection,
ensuring the seal provided is correctly located.
3. Fit the filling loop provided between the DHW inlet valve and
the CH return valve

GAS CONNECTION
IMPORTANT.
The gas service cock is sealed with a non-metallic
blue fibre washer, which must not be overheated when making
capillary connections. Refer to Frame 1 for details of the position
of the gas connection.

Important - when filling:
When filling, there may be a slight water leak from the air vent
therefore electrical connections should be protected.
1. Ensure Filling Loop is connected
2. Ensure dust cap on auto air vent is slackened off (refer to
Frame 66).
3. Check all isolation handles on all water connections are in
the open position.
4. Open handle  on the filling loop, then slowly open handle
 until pressure gauge reads between 1 to 1.5 bar.
5. Once pressure gauge dial reads between 1 - 1.5 bar turn the
filling loop isolation valves back to the closed position.
6. Disconnect filling loop at the LH side, ensuring top hat
washer is retained and screw on blanking cap.
7. Connect extended blanking cap and top hat washer to filling
loop pipe.
Note. Fully open all DHW taps and ensure water is
flowing freely. Once satisfied close all taps.
Handle 

For additional gas supply info refer to “Gas Supply” on page 8.

(Shown in closed position)

safety valve Drain
The safety valve connection, located at the bottom right-hand
side of the boiler, comprises a 15mm diameter stub pipe.
The Installer to provide a compression joint on the end of the
stub pipe. This assists with pipe removal when servicing.
The discharge pipe should be positioned so that the discharge
of water or steam cannot create a hazard to the occupants of
the premises or damage the electrical components and wiring.
CH Flow

DHW
Outlet

Handle 

Gas
Supply

(Shown in closed position)
DHW
Inlet

Black
Handle
Yellow
Handle

CH
Return

Blue
Handle

Note that all isolation handles
are shown in the open postion.

Filling
Loop

Black
Handle
Black
Handle

Safety
Drain
Valve

Keston Combi - Installation and Servicing

23 electrical connections
Warning. This appliance must be earthed.
A mains supply of 230Vac ~ 50 Hz is required.
The fuse rating should be 3A. All external controls and wiring
must be suitable for mains voltage.
Wiring external to the boiler MUST be in accordance with the
current I.E.E. (BS.7671) Wiring Regulations and any local
regulations.

Wiring should be 3 core PVC insulated cable, not less than
0.75mm2 (24 x 0.2mm), and to BS 6500 Table 16. For IE
reference should be made to the current ETCI rules for electrical
installations.
Connection must be made in a way that allows complete isolation
of the electrical supply such as a double pole switch having
a 3mm (1/8”) contact separation in both poles. The means of
isolation must be accessible to the user after installation.

24 internal wiring
The Keston Combi boiler comes pre-fitted with 1.8m of
mains cable. This must be connected to a permanent live
supply and NOT switched by thermostats/programmers.
For installers wishing to change this cable refer to Frame
26.
The Keston Combi boiler comes pre-fitted with a link wire
between the room thermostat/Timer connections on the
terminal strip. This creates a permanent call for heat
and must be removed when adding a room thermostat/
programmer.
The terminal block cover carries two spare fuses for the
main PCB.

To add thermostat/programmer:
1. Isolate the mains supply to the boiler.
2. Remove the front panel. Refer to Frame 39.
3. Swing the control box down into the servicing position.
Refer to Frame 45.
4. Route incoming cables through the grommets in bottom
panel (note, grommets are ‘blind’ and will require puncturing)
and secure using clamps and screws provided in hardware
pack.
5. Pull off rubber terminal block cover.
6. Connect wires to terminal block, as shown below
7. Re-assemble in reverse order.

Spare PCB fuses

continued . . . .

Keston Combi - Installation and Servicing

INSTALLATION

INSTALLATION
INSTALLATION

25 internal wiring.... cont’d
Keston offer 2 kits as follows:
(see individual kits for installation instructions)
Electronic Timer (7 day) kit - 7 day electronic CH timer fits into the control box of the boiler. This can be fitted in conjunction
with a room thermostat. Features English language installation help messages.

DIAGRAM A
Internal Timer or
Programmable Room Stat

(1) Room thermostat with internal boiler timer or
(2) programmable room thermostat

Room
Stat or
Prog.
Room
Stat

1. Remove link wire between room stat/timer terminals.
2. Connect room stat across terminals as shown in diagram A

ROOM
STAT/
TIMER
Optional
Frost Stat

L
N

3G9560

FROST
STAT
(OPTIONAL)

Room Thermostat + timer

DIAGRAM B
External
Timer

N
Room
Stat

1. Remove link wire between room stat/timer terminals.
2. Connect room stat and programmer in series as shown in diagram B.
3. If room stat has a neutral connection, connect this to terminal N (load) in the
fused spur.

ROOM
STAT/
TIMER

frost thermostat
Optional
Frost Stat

L
N

3G9561

FROST
STAT
(OPTIONAL)

L
N

If parts of the system are vulnerable to freezing or the programmer is likely to be
left off during cold weather, a frost stat should be fitted in conjunction with a pipe
thermostat.
1. Position the frost thermostat in a suitable position, i.e. area vulnerable to
freezing.
2. Connect frost stat across terminals marked frost stat shown in diagrams A &
B.

Weather Compensation Kit

DIAGRAM C
Weather Compensation Kit
ROOM
STAT/
TIMER

3. If room stat has a neutral connection, connect this to terminal
N (load) in the fused spur.

Timer
Optional
Frost Stat

The two wires from the weather compensation kit (outside
sensor), must be connected into the two right hand terminals as
shown in diagram C.

OpenTherm
Harness

Outside
Sensor

3G9707a

FROST
STAT
(OPTIONAL)

Weather
Compensation

Keston Combi - Installation and Servicing

INSTALLATION
INSTALLATION

26 rEPLACING PRE-FITTED MAINS CABLE
If it is necessary to use an alternative mains cable to the one pre-fitted
then use the following guide.
Replacement wiring should comply with notes in Frame 23.
1. Isolate the mains supply to the boiler.
2. Remove the front panel. Refer to Frame 39.
3. Swing the control box down into the service position. Refer to
frame 45.

4. Remove the live, neutral and earth wires from the terminal block.
5. Loosen the cable clamp and withdraw the mains cable.
6. Route replacement cable back through the cable clamp and
grommet and re-tighten to provide cord anchorage.
7. Connect the live, neutral and earth wires to the terminal strip.

When making the mains electrical connections to the boiler it is
important that the wires are prepared in such a way that the earth
conductor is longer than the current carrying conductors, such that
if the cord anchorage should slip, the current carrying conductors
become taut before the earthing conductor.

8. Swing the control box back up into the operating position and re-fit
the front panel ensuring a good seal is made.

27 FITTING THE WEATHER COMPENSATION KIT - supplied as standard
This kit provides the facility to apply outside air temperature control to the boiler
water flow temperature which provides energy savings. The outside sensor provided
measures outside air temperature and sends a signal to the boiler, which adjusts the
maximum boiler flow temperature in response. If outside air temperature is greater than
the system design temperature, the boiler flow temperature is reduced providing running
cost savings. The boiler will operate in the condensing mode more frequently increasing
savings.

Kit Contents
A. Outside Air Sensor
A

Once the sensor is fitted it is automatically detected.
The sensor operation may be configured by adjustment of the boiler operating
parameters, if necessary.

fitting the kit

3G10011

Note. A timer should be fitted to the system so that CH will be switched off when appropriate.
Fitting the sensor
The air sensor should be located on an external wall of the building to be heated. Fix the sensor to a north/north-east facing wall
to avoid direct radiation from the sun. The air sensor should be located to avoid any heating effect from the boiler flue.
To fix the air sensor to the wall, unscrew the sensor box plastic cover and screw/plug the sensor body to the wall.
Wire a twin core 0.5mm2 cable from the sensor to the boiler through an RH grommet located on the underside of the boiler. Cable
length between sensor and boiler should be no greater than 20m. Note that this connection is safety extra low voltage. It is not
necessary for the person carrying out the wiring to be approved to Part P of the Building Regulations.
Avoid running this cable alongside mains voltage cables.
Wiring the Weather Compensation Kit to
the Keston Combi.

1. Isolate the electricity supply to the boiler.
2. Remove the boiler front panel (refer to
boiler installation instructions).
3. Hinge down the control box.
4. Connect the sensor wiring into the RHS of
the 4 way terminal block and secure with a
cable clamp.
5. Re-assemble in reverse order.

Keston Combi - Installation and Servicing

28 CH Operation
The On and Off time control of central heating should be controlled by a separate timer. This can be a standard unit or either of
the options available from Keston Combi range.
During programmed On times the Central Heating Radiator Flow Temperature is controlled by the boiler relative to the Outside
Temperature as shown in the following diagram.
Weather Compensation Control / Room Setpoint = +20ºC
CH Temperature Setpoint [C]

INSTALLATION

Heating slope

2.5

2.2 2.0

1.8

1.6

1.4

1.2

1.0

100
90
80
70
60
50
40
30

-10

-20

-30

20
-40

Outside Temperature [ºC]

The Room temperature can be adjusted using the Central Heating Temperature Control Knob on the boiler as follows.
Essentially rotating the knob clockwise increases the room temperature and rotating the knob anti-clockwise decreases the room
temperature.
If the Central Heating Temperature Control Knob is rotated fully clockwise then for an Outside Temperature of 15°C a Flow
Temperature of 40°C will be provided. For an Outside Temperature of 0°C a Flow Temperature of 78°C will be provided with the
relationship varying lineally in between these 2 points (line on the graph 2.5)
If the Central Heating Temperature Control Knob is in its mid position then for an Outside Temperature of 15°C a Flow
Temperature of 36°C will be provided. For an Outside Temperature of 0°C a Flow Temperature of 65°C will be provided with the
relationship varying lineally in between these 2 points (line on the graph between 1.6 and 1.8)
If the Central Heating Temperature Control Knob is rotated fully anti-clockwise then for an Outside Temperature of 15°C a Flow
Temperature of 30°C will be provided. For an Outside Temperature of 0°C a Flow Temperature of 44°C will be provided with the
relationship varying lineally in between these 2 points (line on the graph 1.0)

Keston Combi - Installation and Servicing

INSTALLATION

Wiring External to the Boiler
The fuse rating should be 3A.

Programmable Room Stat

Wiring external to the boiler MUST be in accordance with
the current I.E.E. (BS.7671) Wiring Regulations and any
local regulations.

Programmable
Room
Stat

Frost Protection
If parts of the pipework run outside the house or if the
boiler will be left off for more than a day or so then a frost
thermostat should be wired into the system.
This is usually done at the programmer, in which case the
programmer selector switches are set to OFF and all the
other controls MUST be left in the running position.
The frost thermostat should be sited in a cold place but
where it can sense heat from the system.
Note. If the boiler is installed in a garage it may be
necessary to fit a pipe thermostat, preferably on the return
pipework.

INSTALLATION

29 external electrical controls

Optional
Frost Stat

Mains In

Room Stat

Frost Stat

Use of General Live for Room Stat
Room
Stat

Earths are not shown for clarity but must never be
omitted.

Optional
Frost Stat

Mains In

Room Stat

Frost Stat

3G9990a

OpenTherm Programmable Room Temperature Control
7

Note. These terminals MUST ONLY be connected to an
OpenTherm Controller, (such as the Keston Chronothern Room
Controller (c.17.4.21.00.0). Connecting any other device /
control wiring may destroy the primary PCB.
1. Isolate the mains supply to the boiler.
2. Remove the front panel. Refer to Frame 39.
3. Swing the control box down into the servicing position. Refer
to Frame 45.

4. Remove the control box cover. Refer to Frame 57, no’s 3
and 4.
5. Unclip the 3 way in-line connector containing 2 purple wires
and 2 red wires.
6. Connect this 3 way connector to the 3 way connector
containing 2 purple wires wired from the 4 way terminal
block.
7. Connect the two wires from the OpenTherm Programmable
Room Temperature Control to the two LH connections of the
terminal block as shown.
8. Re-assemble in reverse order.

Keston Combi - Installation and Servicing

Water
Flow
Turbine

Flow
Return
Water
pressure Thermistor Thermistor
Sensor

r
bk

bk g

Weather
Compensation

bk v

Selv Timer

Service
Connector

Fan

9
y/g

y/g

Spark
Electrode

PCB

Flame
Sensor y/g
Electrode

y/g

Opentherm
Room Thermostat

bk g

11 10 9 8 7 6 5 4 3 2 1 6 5 4 3 2 1 4 3 2 1 5 4 3 2 1

KEY
b - blue
bk - black
br - brown
r
- red
p - pink
y - yellow
w - white
y/g - yellow/green
g - grey
or - orange
v - violet

Spark
Generator

y/g

Gas
Valve

bk
br

Divertor
Valve

Flue
Thermostat

Earth

3
br

Pump

y/g

Frost
Stat

Main
Supply

y/g

Room
Stat

b
r

Timer

INSTALLATION

30 wiring diagram

Keston Combi - Installation and Servicing

31 Commissioning and Testing
A. Electrical Installation

B. Gas Installation

1. Checks to ensure electrical safety should be carried out by a
competent person.

1. The whole of the gas installation, including the meter,
should be inspected and tested for tightness and purged in
accordance with the recommendations of BS. 6891.
In IE refer to IS.813:2002.

2. Always carry out the preliminary electrical system checks,
i.e. earth continuity, polarity, resistance to earth and short
circuit, using a suitable test meter.
3. After wiring the boiler, all grommets in the bottom panel MUST
be in place to ensure that the boiler case sealing is maintained.

2. Purge air from the gas installation by the approved methods
only.

WARNING. Whilst effecting the required gas tightness test and purging air from the gas installation,
open all windows and doors, extinguish naked lights and do not smoke.

General

“Service RequireD” Function

Please Note: The combustion for this appliance has
been checked, adjusted and preset at the factory for
operation on the gas type defined on the appliance
data plate. No measurement of the combustion is
necessary. Do not adjust the air/gas ratio valve.

When the boiler has been installed for more than 1 year the following
message will appear on the screen:
“12 Month Service Interval Request”
To cancel this message move the CH Temperature Control Knob away
from the maximum position. Then move the knob to the maximum
position, away from the maximum position and back into the maximum
position again within 3s.

Having checked:
- That the boiler has been installed in accordance
with these instructions.
- The integrity of the flue system and the flue seals,
as described in the Flue Installation section.
Proceed to put the boiler into operation as follows:

Check the operational (working) gas
CH Flow
inlet pressure

DHWatOutlet
Set up the boiler to operate
maximum rate by
opening hot tap to maximum
flow.
Gas Supply
With the boiler operating in
the maximum rate condition
check that the operational
(working) gas pressure at
the inlet gas pressure
Blacktest
point complies with
the
Handle
requirements - refer to “Gas Yellow
Handle
Supply” on page 8.
Ensure that this inlet pressure
can be obtained with all other
gas appliances in the property
working.

Gas Pressure
Test Point

“Service Mode” will be shown on the screen, this will disappear after
5 mins.

“Air Venting” Function
The Air Venting function should not be required for this boiler.
• The Air Venting function operates for 5 mins as follows:
• Pump On for 50s, Pump Off for 10s (repeats 5 times)
• Diverter valve in hot water position for 30s then CH position for
30s (repeats 5 times)
• The function ends automatically.
To activate the Air Venting function proceed as follows:
DHW Inlet
Turn the DHW temperature control knob fully anti-clockwise.
Return
Turn the CHCH
flow
temperature control knob fully anti-clockwise.
Turn and hold the Mode Knob in the Reset position for more than 5s
and then turn it to the Winter or Summer position
The boiler will display “Installer Mode”
If no faults have occurred the boiler will display “No Faults”
If any faults have occurred a list of faults
up to a maximum of 10
Safety
Blue the type of fault and how long
including
ago it occurred will be shown.
Drain
Handle
The
boiler will then display the currentValve
values of flow temperature,
Blackhot water temperature, DHW flow rate
return temperature, domestic
Handle
and diverter valve position.
Next the boiler will
display
3G9927a
“Venting Boiler OFF” - “For Activation change Pre-heat Mode”
Now move the pre-heat knob and the Air Venting Function will begin,
the boiler will display:
“Venting Boiler Off” - “Pump and Diverter Valve Cycling” Duration 5 mins” - “Reset to End”

As part of the commissioning process, the combustion of this appliance must be checked
and the Benchmark Checklist completed. A flow chart to assist is provided on page 71.

ATTENTION !

IT IS A CONDITION OF THE MANUFACTURERS WARRANTY THAT THE BENCHMARK
COMMISSIONING CHECKLIST IS FULLY COMPLETED AND LEFT WITH THE APPLIANCE

Keston Combi - Installation and Servicing

INSTALLATION

INSTALLATION
32 initial lighting
Legend
A. Pre-heat On/off
B. DHW temperature control
C. CH temperature control
D. Off/Summer/Winter/Reset Control
E. Boiler Status
F. Burner ‘on’ indicator
G. CH Flow Isolating Valve
H. Pressure Gauge
J. Gas Inlet Pressure Test Point
K. Gas Service Cock
L. DHW Inlet Valve
M. CH Return Isolating Valve
N. DHW Outlet

L
M

1. Check that the system has been filled and that the boiler is not
airlocked. Ensure the automatic air vent cap is open. Refer to
Frame 22.
Note.
It is important the burner is not operated before the system is
fully vented of air. If it is necessary to operate the appliance
pump to assist venting of the air this must be done with the gas
service cock turned off.
2. Refit the boiler front panel. Refer to Frame 39.
3. Check that the drain cock is closed and that the CH and DHW
isolating valves (M, L and G) are OPEN.

N
K

DOMESTIC HOT WATER
11. With the boiler firing, set the DHW Temp Control knob (B)
to maximum and fully open a DHW tap.

The boiler will continue to run and the display (E) will
show “Hot Water” - “Temperature XXoC” - “High
Efficiency”.

12. Ensure that with the boiler operating the dynamic gas
pressure is able to obtain maximum output. Refer to Table
2.

7. Slacken the screw in the inlet pressure test point (J) and
connect a gas pressure gauge via a flexible tube.

Important
The gas input to the burner is regulated by the gas valve
according to the air flow produced by the fan. It is not
user-adjustable. Any interference to sealed settings on
the gas valve will adversely affect operation and render
our warranty void.

8. Switch the electricity supply ON and check all external controls
are calling for heat.

For additional gas supply information refer to “Gas Supply” on
page 8

4. Check that the electrical supply is OFF.
5. Check that the boiler mode control knob (D) is off.
6. Check that the gas service cock (K) is OPEN.

13. Turn off the DHW tap.
Central Heating
9. Set the CH temp control (C) to max and turn the mode control
knob (D) to , ensure the timer/room stat are on. The boiler
control will now go through its ignition sequence until the
burner is established.
10. If the boiler does not light the following messages will be
displayed in rotation “Ignition Lockout” - “1 Check
other gas appliances” - “2 Reset boiler” - “3 Contact
installer”. After 5 attempts the boiler will lock out and carry
on displaying the messages. Reset the boiler (refer to Frame
40B). The boiler will repeat its ignition sequence. If reset
occurs 5 times within 15 minutes then “Too many resets”
will be shown. If power is removed this will be reset.

When the burner is established the BLUE ‘Burner On’ neon
(F) will be illuminated, the LCD will display “Central Heating”
and “Radiator Temp XXoC”.

Note. The temperature displayed “XXºC” is that
measured at that moment, not the set temperature.
Note. The boiler incorporates a fan overrun cycle
which MUST NOT be prematurely interrupted by
isolation of the mains electricity supply.

continued. . . . .

Keston Combi - Installation and Servicing

33 initial lighting . . . . cont’D
THE DISPLAY
The user control has one neon and one display to inform the user about the status. The display will show the status of the boiler.
The neon will show the status of the flame. If no flame is detected the neon is off. When the flame is detected the neon will be lit
permanently.
The display scrolls through a maximum of 3 messages under any operational condition as shown below.
Notes: Boiler frost protection - boiler fires if temperature is below 5º C.

The temperatures shown below are for illustration purposes only. The measured temperatures will be shown on the boiler.
DISPLAY FUNCTIONS IN NORMAL OPERATION

MESSAGE 1

MESSAGE 2

MESSAGE 3

Mode knob in standby position and no
heat demand

Standby mode

For hot water turn mode
knob clockwise

For central heating turn
mode knob clockwise twice

Mode knob in summer position and no
heat demand

Summer mode

For central heating turn
mode knob clockwise

Mode knob in winter position and no
heat demand

Winter mode

Timer or room stat off

Domestic hot water operation

Hot water

Temperature 64ºC

High efficiency

Central heating operation

Central heating

Radiator Temp 80ºC

High efficiency

Pre-heat operation

Pre heat

Temperature 59ºC

High efficiency

Boiler frost protection

Temperature 5ºC

High efficiency

Pump overrun

Fan post-purge

3G9711

NORMAL OPERATION

Note. High efficiency will not be shown for central heating operation if the central heating flow temperature knob is set to greater than 73ºC.

NORMAL OPERATION

MESSAGE 1

MESSAGE 2

MESSAGE 3

Pre-heat knob moved to off position

Pre heat off

Pre-heat knob moved to on position

Pre heat on

DHW temperature knob moved

64ºC DHW temp

Hot water
temperature 64ºC

May not be achieved for
high flow rates in winter

CH temperature knob moved

80ºC CH temp

Maximum radiator
temperature 80ºC

Mode knob moved to standby position

Standby mode

Central heating off

Hot water off

Mode knob moved to summer position

Summer mode

Central heating off

Hot water on

Mode knob moved to winter position

Winter mode

Central heating on

Hot water on

Mode knob moved to reset position

Reset

Keston Combi - Installation and Servicing

3G9712

DISPLAY FUNCTIONS - SETTINGS CHANGED

INSTALLATION

34 initial lighting . . . . cont’D
INSTALLER MODE
Installer Mode is entered as follows:
1. Turn the DHW temperature control knob full anti-clockwise.
2. Turn the CH flow temperature control knob full anti-clockwise.
3. Turn and hold the mode knob in the reset position for more than 5 secs and then turn it to the Winter or Summer position.
The boiler will display “Installer mode”.
If no faults have occurred the boiler will display “No faults”.
If any faults have occurred a list of faults up to a maximum of 10 including the type of fault and how long ago it occurred will be
shown in the following format.

MESSAGE 1

MESSAGE 2

MESSAGE 3

Fault 1 (latest fault)

Low water pressure

2 days ago

Fault 2

No water flow lockout

78 days ago

Fault 3

Overheat lockout

384 days ago

The boiler will then display the current values of
flow temperature, return temperature, domestic hot
water temperature, DHW flow rate and diverter valve
position in the following format:

3G9713a

LIST OF FAULTS

Note.
If you would like to hold one of the values on the display to watch
its behaviour then turn the reset knob to the reset position while it is
displayed and hold it there.

MESSAGE 1
CURRENT VALUES

Finally the display will operate in one of two modes. If there is a
fault then more extensive corrective actions will be shown than are
usually displayed for the end user. If there is not a fault then the
information displayed for current operating states will also be more
extensive than is usually displayed for the end-user (pre-purge,
ignition and post purge for example).

Flow temp 80ºC
Return temp 60ºC
DHW temp 64ºC
DHW flow rate 8 l/min

Installer mode automatically ends after 10 mins or by moving the
mode knob to the standby position.

3G9714

INSTALLATION

Diverter valve DHW position

35 RESET PROCEDURE
To reset boiler, turn the mode control knob (D) to reset position and immediately turn knob back to required setting. The boiler will
repeat the ignition sequence if a heat demand is present.

Legend
A. Pre-heat On/off
B. DHW temperature control
C. CH temperature control

D. Off/Summer/Winter/Reset Control
E. Boiler Status
F. Burner ‘on’ indicator

Keston Combi - Installation and Servicing

36 general checks
Make the following checks for correct operation in:
Domestic hot water (dhw) mode
1. Fully open all DHW taps in turn and ensure that water flows
freely and that the mode knob is either in summer or winter
position. The boiler will display

“Hot Water” - “Temperature XXoC” - “High
Efficiency”

where the temperature shown is the current Domestic Hot
Water temperature.

When the burner is lit the light above the display will be on.

2. Close all taps except the furthest one from the boiler and
check that the boiler is firing at maximum rate.
This is factory set to give a DHW temperature rise of
approximately 35oC at the flow rate stated on page 6 under
“operation”.
3. Reduce the DHW draw-off rate to about 3 l/min (0.7gpm)
and check that the boiler modulates to deliver DHW at
approximately 64oC (with the DHW temperature control
knob set to maximum).
4. Close the DHW tap and check that the main burner
extinguishes. The pump should overrun for 60 seconds
during which the boiler will display “Pump overrun”. The
fan will then continue to run for a further 3 minutes during
which the boiler will display “Fan Post Purge” after which
the boiler will display one of the following “Standby mode”
- “Summer mode” - “Winter Mode” depending on the
position of the mode knob.
Note. On systems in excess of 2 bar inlet pressure a water
pressure governor may be required to prevent water noise.

CH & DHW mode
1. Ensure the CH controls are calling for heat and that the
boiler mode knob is in the winter position and the CH flow
temperature control knob is in the maximum position. The
Boiler will display

“Central Heating” - “Radiator Temp XXC”

where the temperature shown is the current flow temperature.

When the burner is lit the light above the display will be on.

2. Fully open the DHW tap and check that hot water is delivered.
The boiler will display “Hot water” - Temperature XXoC”
- High Efficiency”
3. Gas Rate

Check the boiler gas rate when the boiler is at full DHW
output. Check at the gas meter, with no other appliance in
use. Refer to Tables 2 and 3 for gas rates.

4. Close the DHW tap. The burner should remain on and the
boiler will display “Central heating” - “Radiator temp
XXC”.
5. Set the central heating external controls to off. The burner
will go off and the fan and pump continue to run for 4 minutes.
The boiler will display “Pump overrun” after which the
boiler will display one of the following: “Standby mode”
- “Summer mode” - “Winter mode” depending on the
position of the mode knob.
6. Check the correct operation of the timer (if fitted) and all other
system controls. Operate each control separately and check
that the main burner responds.
Note. The temperature displayed “XXºC” is that
measured at that moment, not the set temperature.

Water circulation system

8. Finally, set the controls to the User’s requirements.

1. With the system COLD, check that the initial pressure
is correct to the system design requirements.

Notes.
1. If the pump has not operated in the last 24 hours it will run
briefly to prevent seizure

For pre-pressurised systems, this should be 1.0 bar.

2. With the system HOT, examine all water connections
for soundness. The system pressure will increase
with temperature rise but should not exceed 2.5 bar.

2. If the diverter valve has not operated in the last 24 hours
it will be operated briefly to prevent seizure. These two
operations will not occur at the same time.

3. With the system still hot, turn off the gas, water and
electricity supplies to the boiler and drain down to
complete the flushing process.
Note: A flushing solution should be used during the
flushing procedure. Flushing solutions: Fernox
Superfloc, Sentinel X300 (new systems) or X400
(existing systems). Refer to Frame 5.
4. Refill and vent the system, add inhibitor (see Frame
5), clear all air locks and again check for water
soundness.
5. Reset the system initial pressure to the design
requirement.

Water temperatures
Temperatures can be selected using the CH and DHW thermostats.
Knob Setting

CH Flow Temp
o
C (oF)

DHW Outlet Temp
o
C (oF)

6. Balance the system. Refer to Frame 4.

Max

80 (176)

64 (147)

7. Check the condensate drain for leaks and check that
it is discharging correctly.

Min

45 (113)

40 (104)

Keston Combi - Installation and Servicing

INSTALLATION

INSTALLATION
37 HANDING OVER

After completing the installation and commissioning of the system the installer should hand over to the householder by
the following actions:
1. Make the householder aware that the user instructions
are located in the pocket in the drop down door and
explain his/her responsibilities under the relevant national
regulations.

8. Loss of system water pressure

2. Explain and demonstrate the lighting and shutting down
procedures.
3. The operation of the boiler and the use and adjustment
of all system controls should be fully explained to
the householder, to ensure the greatest possible fuel
economy consistent with the household requirements of
both heating and hot water consumption.

9. Explain boiler reset procedure (refer to Frame 35).
10. After installation and commissioning please complete

Advise the User of the precautions necessary to prevent
damage to the system and to the building, in the event of
the system remaining inoperative during frosty conditions.

Commissioning Checklist before
the
handover to the customer. For IE, its is necessary to complete
a “Declaration of Conformity” to indicate compliance to I.S.
813:2002.

4. Explain the function and the use of the boiler heating and
domestic hot water controls.

Explain that due to system variations and seasonal
temperature fluctuations DHW flow rates/temperature
rise will vary, requiring adjustment at the draw off tap. It
is therefore necessary to draw the users attention to the
section in the Users Instructions titled “Control of Water
Temperature” and the following statement:

“Additionally, the temperature can be controlled by
the user via the draw-off tap: the lower the rate the
higher the temperature, and vice versa”.
5. Explain the function of the boiler fault mode.

Explain that the dial underneath the boiler indicates the
central heating system pressure and that if the normal COLD
pressure of the system is seen to decrease over a period of
time then a water leak is indicated. Explain the re-pressurising
procedure and if unable to re-pressurise or if the pressure
continues to drop a registered local heating installer should be
consulted.

Important
11. A comprehensive service should be carried out ANNUALLY.

Stress the importance of regular servicing by a Gas Safe
Registered Engineer. In IE servicing work must be carried out
by a Registered Gas Installer (RGII).

12. Inform the householder of the guarantee form and the
requirement to register it to receive the full benefit of the
warranty.

Emphasise that if a fault is indicated, the boiler should be
turned off and a Gas Safe Registered Engineer consulted.
In IE contact a Registered Gas Installer (RGII).

6. Explain and demonstrate the function of time and
temperature controls, radiator valves etc., for the
economic use of the system.
7. If a timer is fitted draw attention to the timer Users
Instructions and hand them to the householder.

Keston Combi - Installation and Servicing

SERVICING
38 servicing schedule
For the very latest copy of literature for specification & maintenance practices, visit our website www.keston.co.uk, where you will
be able to download the relevant information.
Warning. Always turn off the gas supply at the gas service cock, and switch OFF and disconnect the electricity
supply to the appliance before servicing.
Combustion testing must be carried out by a competent person using a combustion analyser conforming to BS7927.
To ensure the continued safe and efficient operation of the appliance it is recommended that it is checked at regular intervals and
serviced as necessary. The frequency of servicing will depend upon the installation condition and usage but should be carried out
at least annually.
It is the law that any service work must be carried out by a Gas Safe Registered Engineer. In IE service work must be carried out
by a Registered Gas Installer (RGII).
1. Light the boiler and carry out a pre-service check, noting any
operational faults.
2. Check the flue terminal (and terminal guard if fitted) is undamaged
and clear of any obstruction.

General
Please Note: During routine servicing, and after any
maintenance or change of part of the combustion
circuit, the following must be checked:
- The integrity of the flue system and the flue seals,

3. Check all water and gas joints for signs of leakage. Remake any
suspect joints ensuring a gas tightness check is carried out if
applicable and the water system is correctly refilled, vented and
re-pressurised.

- The integrity of the boiler combustion circuit and
the relevant seals

CLEANING PROCEDURE

- The gas rate

Note. In order to carry out either servicing or replacement of
components the boiler front panel must be removed. Refer to
Frame 39.
1. Clean the main burner. Refer to frame 41.
2. Clean the heat exchanger & condensate trap/siphon. Refer to
Frames 41 & 42.
3. Check the main injector for blockage or damage. Refer to Frame
40.
4. Check that the flue terminal is unobstructed and that the flue system
is sealed correctly.
ALSO IF THE DHW FLOW RATE IS IN QUESTION :5. Check the DHW filter for blockage. Refer to Frame 70.
The cleaning procedures are covered more fully in Frames 40-45 and
must be carried out in sequence.
Important.
6. After completing the servicing or exchange of components always
test for gas tightness.
7. When work is complete the front panel MUST be correctly refitted,
ensuring that a good seal is made.

- The operational (working) gas inlet pressure at
maximum rate.
- The combustion performance.

Competence to carry out the check
of combustion performance
Please Note:
BS 6798:2009 Specification for
installation and maintenance of gas-fired boilers of
rated input not exceeding 70kW net advises that:
- The person carrying out a combustion
measurement should have been assessed as
competent in the use of a flue gas analyser and the
interpretation of the results.
- The flue gas analyser used should be one meeting
the requirements of BS7927 or BS-EN50379-3
and be calibrated in accordance with the analyser
manufacturers requirements, and
- Competence can be demonstrated by satisfactory
completion of the CPA1 ACS assessment, which
covers the use of electronic portable combustion
gas analysers in accordance with BS7967, Parts 1
to 4.

Do not operate the boiler if the front panel is not
fitted.
8. If, for any reason, the condensate trap/siphon has been removed
ensure the trap is refilled with water before
reassembling.
9. Check the gas consumption.
10. Check combustion by connecting the flue gas analyser to the flue
gas sampling point as shown in the diagram and measure CO &
CO2.

If the CO/CO2 ratio is greater than 0.004 AND the integrity of the
complete flue system and combustion circuit seals have been
verified and the inlet gas pressure (and gas rate) have been
verified, then contact Keston.

11. Complete the service section in the Benchmark Commissioning
Checklist.

Keston Combi - Installation and Servicing

Servicing

INSPECTION

SERVICING
39 boiler front panel removal / Replacement
1

REMOVAL
1. Loosen the two screws retaining the front panel.

2. Pull the two spring clips down to disengage and pull panel
forward and upward and remove.
REPLACEMENT
3. Hook the panel onto the top retaining clips.
4. Push the panel until the 2 bottom spring clips engage
ensuring the 4 control knobs line up with the holes in the
front panel.
5. Re-tighten the two retaining screws.

servicing

view from bottom of boiler

view from top of boiler

40 fan and venturi assembly removal and cleaning
1. Disconnect the electrical leads from the fan.
2. Undo the gas pipe union connection to the
injector housing.

3. Remove the extended nut on the fan
mounting bracket.
4. Lift off fan and venturi assembly.
5. Inspect the injector for blockage or damage.
6. Inspect fan outlet sealing gasket and
replace if necessary.
5

Injector

Keston Combi - Installation and Servicing

SERVICING
41 burner removal and cleaning
1. Ensure the sump is fully drained

2. Undo the two screws and remove the sump cover retaining the lower
flue manifold.

3. Lift the manifold to clear the bottom sealing gasket and remove
manifold.
4. Remove the 2 burner front fixing screws and loosen the 2 rear
extended nuts by at least ten turns.
5. Lift off the burner from the combustion chamber. To facilitate the
removal angle the burner as shown.
Important
The burner head is a ceramic plaque construction. Care must be
taken to ensure that the burner is not placed down upon
its face as this may cause damage to the ceramic.

6. Brush off any deposits that may be on the ceramic with a
SOFT brush.

Servicing

7. Inspect the sealing gasket around the burner for any
signs of damage. Replace as necessary.

42 cleaning the condensate Trap/Siphon
1. Pull off the rubber pipe at the sump drain.

4. Clean siphon with water.

2. Disconnect the condensate drain pipe.

5. Re-assemble in reverse order.

3. Turn the siphon clockwise to disengage and lift to
remove.

B When re-assembling ensure the trap is full of water.

Note. Keep siphon upright when removing
1

3G9690

Keston Combi - Installation and Servicing

SERVICING
43 cleaning the heat exchanger
Note: Ensure the condensate trap/siphon
is fully drained before cleaning. Refer to
Frame 61.

1
Ignition Electrode

Flame Detection

1. Remove ignition and flame detection
electrodes. Refer to Frames 51 & 52.
2. It is advisable to replace the sump cover
prior to the water flush process.
3. Thoroughly flush the heat exchanger
by pouring water into the top of the
combustion chamber ensuring the full top
area is covered.
4. Remove the sump cover and clean loose
deposits from the sump.
3

Servicing

5. Inspect the ignition and detection
electrodes. Ensure that they are clean
and in good condition - replace if
necessary.
6. Re-fit the ignition and flame detection
electrodes, ensuring that both earth tabs
are fitted to ignition electrode.
7. Check that the ignition and detection gaps
are correct. Refer to Frames 51 & 52.

44 reassembly
Reassemble the boiler in the following order:
1. Ensure that the condensate trap/siphon is full of water.

6. Refit the sump cover.

2. Refit the burner ensuring the sealing gasket is correctly
positioned and free from damage (tighten the 4 fixing screws
in the sequence shown below).

7. Refit the boiler front panel.
Important. Ensure that the boiler front panel is
correctly fitted and that a good seal is made.

3. Refit the fan / venturi assembly ensuring the retaining tabs
are correctly positioned and the sealing gasket is correctly
positioned and free from damage.

8. Swing the control box back into its working position and
secure.

4. Reconnect the fan electrical leads.

9. Turn on the gas supply at the gas service cock.

5. Remove the sump cover and refit the lower flue manifold as
shown.

10. Reconnect the electrical supply.

Keston Combi - Installation and Servicing

SERVICING
45 replacement of components
General

After replacing ANY component check operation of the
boiler, including gas tightness, gas rate and combustion
test.

When replacing ANY component
1. Isolate the electricity supply.

Important.
When work is complete, the front panel must be correctly
refitted - ensuring that a good seal is made.

2. Turn off the gas supply.
3. Remove the boiler front panel. Refer to Frame 39.

Notes.
1. In order to assist fault finding, the control panel has
an LED diagnostic display. The key to boiler fault
conditions is shown in Frame 75.

4. Release the retaining clip and swing the control box down
into its servicing position.

servicing

2. In order to replace components in Frames 61-72 it is
necessary to drain the boiler. Refer to Frame 60.

THE BOILER MUST NOT BE OPERATED without THE FRONT PANEL FITTED

46 fan replacement

Retaining Tabs
2

1. Refer to Frame 45.
2. Disconnect the electrical leads from the fan.
3. Undo the gas pipe union connection to the
injector housing.
4. Remove the extended nut retaining the fan
mounting bracket.

5. Lift and remove the fan and venturi assembly.
6. Remove the screw and twist venturi anticlockwise to remove venturi assembly, noting
the orientation of the venturi in relation to the
fan body.

7. Transfer the venturi assembly to the new fan,
replacing the ‘o’ ring if evidence of damage or
deterioration is visible.
8. Fit the new fan / venturi assembly ensuring the
retaining tabs are correctly positioned and the
fan outlet sealing gasket is correctly positioned
and free from damage. Refit the extended nut.
9. Reassemble the boiler in reverse order, taking
care not to overtighten the screw on the fan
mounting bracket.

10. Check the operation of the boiler. Refer to
Frame 36.

Keston Combi - Installation and Servicing

SERVICING
47 Burner injector replacement
1. Refer to Frame 45.

2. Disconnect the electrical leads from the fan.
3. Undo the gas pipe union connection to the
injector housing.
4. Loosen the screw retaining the fan mounting
bracket.
5. Lift and remove the fan and venturi assembly.
6. Remove the 2 injector housing screws.
7. Withdraw the injector housing.

8. Fit the new injector housing complete with
injector.
9. Reassemble in reverse order, ensuring that the
new gas seal supplied is located correctly in the
injector housing.
10. Check operation of the boiler. Refer to Frame 36.

Servicing

48 burner REPLACEMENT
1. See Frame 39.
2. Refer to Frame 45.
3. Disconnect 2 flag terminals from the flue thermostat.

5
4

4. Undo the two screws and remove the sump cover.
5. Lift the manifold to clear the bottom sealing gasket and remove
manifold.
6. Remove the 2 front fixing screws and loosen the 2 rear
extended nuts.
7. Lift off the burner from the combustion chamber. To facilitate
the removal angle the burner as shown.
8. Fit the new burner, replacing any damaged or deteriorating
sealing gasket.
9. Reassemble in reverse order. Refer to Frame 44.

10. Check the operation of the boiler. Refer to Frame 36.
7

Keston Combi - Installation and Servicing

SERVICING
49 return thermistor reNEWAL
1. Refer to Frame 44.
2. Unclip the return thermistor from the return pipe and withdraw it from the
boiler.
3. Disconnect the electrical lead from the thermistor.
4. Reconnect the electrical lead to the new thermistor and reassemble in
reverse order, ensuring that the thermistor is securely fitted to the pipe on the
thermistor locator tabs as shown.
5. Check the operation of the boiler. Refer to Frames 29-35.

5
Thermistor Locator Tab
(with thermistor fitted)

servicing

50 flue thermostat replacement
1. Refer to Frame 45.
2. Undo the two screws and remove the
sump cover plate.
3. Disconnect the two flag terminals
from the flue thermostat.
4. Lift the manifold to clear the bottom
sealing gasket and remove manifold.
.
5. Unscrew the two M3.5 screws
that connect the thermostat to the
manifold.
6. Replace thermostat with new part
and then refit the two screws,
remembering to fit rubber gasket and
sealing clamp.

Flue Thermostat

Keston Combi - Installation and Servicing

SERVICING
51 ignition electrode replacement
1. Refer to Frame 45.
2. Remove the burner. Refer to Frame 48.
3. Unplug the ignition lead from the electrode.

Ignition Electrode

4. Remove the earth lead from the ignition
electrode.
5. Remove the 2 screws holding the ignition
electrode to the combustion chamber.
6. Remove the electrode.
7. Fit the new ignition electrode, using the new
gasket supplied. Check dimensions as shown.
8. Reassemble in reverse order.
9. Check the operation of the boiler. Refer to
Frame 36.

e
dg
te
h
aig
Str

Servicing

Spark Gap
3.5mm

52 flame detection electrode replacement
1. Refer to Frame 45.
2. Remove the burner. Refer to Frame 48.
3. Unplug the flame detection lead from the
electrode.

Flame Detection Electrode

4. Remove the 2 screws retaining the detection
electrode.
5. Remove the electrode.
6. Fit the new flame detection electrode, using the
new gasket supplied.
7. Reassemble in reverse order.
8. Check the operation of the boiler. Refer to
Frame 36.

e
dg
te
h
aig
Str

m
2.5

Keston Combi - Installation and Servicing

SERVICING
53 Spark generator replacement
1. Refer to Frame 45.
2. Disconnect the leads from the spark
generator.
3. Remove the M5 screws securing the
spark generator to the boiler chassis.
4. Fit the new spark generator and reassemble in reverse order ensuring
the two earth leads are correctly
replaced.
5. Check operation of the boiler. Refer
to Frame 36.

Spark Generator
4

servicing

54 gas control valve replacement
1. Refer to Frame 45.

2. Unplug the electrical plug connection from the
gas control valve and disconnect the earth wire.
3. Undo the union nut on the outlet of the gas
control valve.
4. Undo the gas inlet pipe union at the inlet to the
gas control valve.
5. Loosen the back nut retaining the valve to the
bracket and withdraw the valve forwards.
6. Fit the new gas control valve ensuring the two
sealing washers are in place and reconnect gas
and electrical connections.
7. Check operation of the boiler. Refer to Frame
36.

2
4

Keston Combi - Installation and Servicing

SERVICING
55 diverter valve actuator replacement
1. Refer to Frame 45.
2. Remove the electrical plug.
3. Using a suitable tool pull out the retaining
clip and lift the diverter head from the brass
body.
4. Fit new actuator head and reassemble in
reverse order.
Diverter Valve Actuator

Servicing

6. Check operation of the boiler. Refer to
Frame 36.

Retaining Clip

56 condensate trap/Siphon replacement
1. Refer to Frame 45.
2. Pull off the rubber pipe at the sump drain.

3. Disconnect the condensate drain pipe.
4. Turn the siphon clockwise to disengage and lift to remove.
Note. Keep siphon upright when removing
5. Clean siphon with water.
6. Re-assemble in reverse order.
7. When re-assembling ensure the trap is full of water.
8. Check operation of the boiler. Refer to Frame 36.

Siphon

3G9690

Keston Combi - Installation and Servicing

SERVICING
57 mAIN pcb rEPLACEMENT
Note. Fit the earth strap provided with the PCB to your wrist and secure to a suitable earth on the boiler chassis.
1. Refer to Frame 45.

8. Re-connect all plug connections.

2. Note the control knob positions.

9. Reassemble in reverse order.

3. Remove the 2 screws retaining the control box cover.

10. Turn power back on to the boiler, after a few moments the
display will start alternating between “c” and “0”. Turn the
reset knob fully clockwise and when the display shows “ - ”
turn the knob fully anti-clockwise IMMEDIATELY.

4. Carefully lift the 4 retaining clips and remove control box
cover.
5. Unplug all lead connections to the PCB including the ribbon
cable (to facilitate ribbon cable removal, ease side clips
apart and pull upwards), also where applicable, push the
small plastic clip with an electrical screwdriver to facilitate
plug removal.

Finally move the knob into the required position (Standby,
Summer or Winter).

11. Check operation of the boiler. Refer to Frame 36.

6. Spring out the two side retaining clips and pull the PCB
upwards to clear the 4 corner retaining posts.
7. Take the new Primary PCB and attach the appropriate Boiler
Chip Card (BCC).
Note. Ensure the correct orientation of BCC by placing
“TOP” side up as shown.

servicing

5
6
5

Plastic
Clip
Ribbon Cable Connection
7

Keston Combi - Installation and Servicing

SERVICING
58 User control PCB replacement
Note. Fit the earth strap provided with the PCB
to your wrist and a suitable earth on the boiler
chassis.
1. Refer to Frame 45.
2. Remove the main PCB, refer to Frame 57.
3. Unclip the PCB and lift to clear the mounting
posts.
4. Fit the new PCB ensuring the 4 potentiometer
spindles line up with the control knobs which
must be in a vertical position.
5. Reassemble in reverse order.
6. Check operation of the boiler. Refer to Frame
36.
3

Servicing

4
Potentiometer spindle

PCB

Control Knobs (to be in vertical position)

59 DHW FLOW TURBINE Sensor REPLACEMENT

1. Refer to Frame 45.
2. Remove condensate trap/siphon. Refer
to Frame 56.
3. Lift off the flow turbine sensor plastic
retaining clip.
4. Unplug the electrical connection and
transfer to new turbine sensor.
5. Reassemble in reverse order.
6. Check operation of the boiler. Refer to
Frame 36.

Keston Combi - Installation and Servicing

SERVICING
60 draining the boiler

CENTRAL HEATING CIRCUIT
1. Refer to Frame 45.
2. Close all the CH water isolating valves on the boiler inlet.
3. To drain the primary heat exchanger circuit: Open the drain
valve and attach a length of hose to the CH drain point.
4. After replacing any component on the boiler, remove the
hose, close the drain valve and open all system isolating
valves (re-pressurise as appropriate by re-connecting the
filling loop, refer to Frame 22) before proceeding to check
operation of the boiler.
6. Check operation of the boiler. Refer to Frames 36.

3G9690

servicing

5. Disconnect filling loop. Refer to Frame 22.

DOMESTIC HOT WATER CIRCUIT
1. Refer to Frame 45.
2. Close all the DHW water isolating valves on the boiler inlet.
3. To drain the domestic hot water circuit: As there is no direct
drain for the domestic hot water circuit, depending on the
location of the boiler, opening the lowest hot water tap
may drain this circuit. However it must be noted that some
residual water will be experienced during replacement of
components.
4. After replacing any component on the boiler, close tap, close
the drain valve and open all system isolating valves (repressurise as appropriate by re-connecting the filling loop,
refer to Frame 22) before proceeding to check operation of
the boiler.

3G9690

5. Disconnect filling loop. Refer to Frame 22.
6. Check operation of the boiler. Refer to Frame 36.

61 Pressure Gauge Renewal
1. Refer to Frame 45.
2. Drain the heating system. Refer to Frame
65.
3. Unscrew the pressure gauge and discard.
4. Fit new pressure gauge, using suitable
jointing compound.
5. Refill the boiler. Refer to Frame 22.
6. Check operation of the boiler. Refer to
Frame 36.

3G9690

Keston Combi - Installation and Servicing

SERVICING
62 safety relief VALVE reNEWAL
1. Refer to Frame 45.

2. Drain the boiler. Refer to Frame 60.
3. Remove the condensate trap/siphon. Refer to
Frame 56.
4. Remove expansion vessel. Refer to Frame 73.
5. Disconnect the electrical connection from the
return thermistor.

6. Disconnect the 22mm pipe connection at the rear
of the pump outlet.
7. Pull off the clip retaining the pipe to the heat
exchanger swing the pipe to clear the pump and
remove pipe.
8. Undo the safety valve union connection.

5
10

Servicing

9. Withdraw the clip securing the safety valve.
10. Lift safety valve from boiler.
11. Fit the new safety valve and reassemble in
reverse order ensuring the new ‘o’ ring is fitted to
the top of the return pipe.
12. Refill boiler. Refer to Frame 22. Check operation
of boiler. Refer to Frames 36.

63 Pump automatic air vent replacement

1. Refer to Frame 45.
2. Drain the boiler. Refer to frame 60.
3. Remove the expansion vessel. Refer to Frame 73.

4. Firstly, increase access area by disconnecting the
22mm pipe connection at top of pump chamber and
bottom of heat exchanger and remove pipe Refer to
Frame 62 (no’s 5,6 & 7).
5. The automatic air vent head is retained in the pump
body with a bayonet connection. The air vent head and
float assembly is removed by turning the head anticlockwise (viewed from above) and pulling upwards.
6. Reassembly is the reverse of the above. Ensure the air
vent head ‘o’ ring seal is in place when refitting and the
new ‘o’ ring is fitted to the return pipe top connection.
7. Ensure the air vent cap is loose.
8. Refill the boiler. Refer to Frame 22. Check for leaks
around the new air vent joint.
9. Check the operation of the boiler. Refer to Frame 36.

Keston Combi - Installation and Servicing

SERVICING
64 DHW FLOW TURBINE CARTRIDGE REPLACEMENT

7
4

1. Refer to Frame 45.
2. Drain the boiler. Refer to Frame 60.
3. Remove condensate trap/siphon. Refer to
Frame 56.
4. Remove the DHW flow turbine sensor. Refer to
Frame 59.
5. Unscrew the top connection to access the
internal part.
6. Fit the new turbine cartridge.
7. Refit the turbine flow sensor
8. Reassemble in reverse order.
9. Refill the boiler. Refer to Frame 22.

65 Diverter Valve internal cartridge replacement
FRONT CARTRIDGE REPLACEMENT

REAR CARTRIDGE REPLACEMENT

1. Refer to Frame 45.

2. Drain the boiler. Refer to Frame 65.

2. Drain the boiler. Refer to Frame 60.

3. Remove the diverter valve head. Refer
to Frame 55.

3. Remove the diverter valve head. Refer to Frame 55.

4. Unscrew the top connection to access
the internal cartridge.

5. Disconnect the CH flow pipe and DHW outlet pipe union connections underneath
the boiler. Refer to Frame 60.

5. Fit the new valve mechanism ensuring
the correct fit of the pin.
6. Reassemble in reverse order.
7. Refill the boiler. Refer to Frame 22.
8. Check operation of the boiler. Refer to
Frame 36.

4. Remove the flow pipe. Refer to Frame 22 no. 12.

6. Remove the plate heat exchanger LH fixing screw. Refer to Frame 66.
7. Remove the screw retaining the brass block to the bottom of the boiler casing
and lift the brass block clear of the boiler.
8. Unscrew the rear cartridge connection.
9. Fit the new valve mechanism ensuring the correct fit of the pin.
10. Reassemble in reverse order.
11. Refill the boiler. Refer to Frame 22.
12. Check operation of the boiler. Refer to
Frame 36.

FRONT CARTRIDGE

Keston Combi - Installation and Servicing

REAR CARTRIDGE

servicing

10. Check operation of the boiler. Refer to
Frames 36.

SERVICING
66 dhw plate heat exchanger replacement
7. Fit the new plate heat exchanger, using the new o-rings
supplied.

1. Refer to Frame 45.
2. Drain the boiler. Refer to Frame 60.

3. Remove condensate trap/siphon. Refer to Frame 56.
4. Remove the diverter valve actuator. Refer to Frame 55.

Note. The mounting pins are offset so the correct position
can be defined from the location of the holes on the brass
mounting.

5. Remove the 2 allen screws securing the plate heat
exchanger to the brass housings.

8. Reassemble in reverse order.

6. Manoeuvre the plate heat exchanger out of the top LH or
centre of the controls area.

10. Check operation of the boiler. Refer to Frame 36.

9. Refill the boiler. Refer to Frame 22.

Servicing

67 Pump Head Replacement
1. Refer to Frame 45.
2. Drain the boiler. Refer to Frame 60.
3. Disconnect the electrical plug from the
pump.

4. Remove the 4 Allen screws retaining the
pump head.
5. Remove the pump head.
6. Fit the new pump head.
7. Reassemble in reverse order.

8. Refill the boiler. Refer to Frame 22.
9. Check operation of the boiler. Refer to
Frame 36.

Keston Combi - Installation and Servicing

SERVICING
68 CH Water Pressure sensor Replacement
1. Refer to Frame 45.
2. Drain the boiler. Refer to Frame 60.
3. Remove condensate trap/siphon. Refer to
Frame 56.
4. Using a suitable tool pull out the retaining clip.
5. Pull the pressure sensor upwards to remove.
6. Unplug the electrical connection and transfer to
the new pressure sensor.

7. Push the new pressure sensor onto the rear
pump housing and fit retaining clip.
8. Reassemble in reverse order.
9. Refill the boiler. Refer to Frame 22.
10. Check Operation of the boiler. Refer to Frame
36.

servicing

69 DHW Filter Cleaning / Replacement
1. Refer to Frame 45.
2. Isolate the mains cold water supply to the
boiler.
3. Drain the boiler DHW circuit. Refer to
Frame 60.
4. Remove the DHW flow turbine cartridge.
Refer to Frame 64.
5. Unscrew the flow regulator housing.
6. Remove the filter.
7. Clean or replace filter as necessary.
8. Reassemble in reverse order.
9. Refill the boiler. Refer to Frame 22.

10. Check Operation of the boiler. Refer to
Frame 36.

Keston Combi - Installation and Servicing

SERVICING
70 DHW Flow REGULATOR Cleaning / Replacement
1. Refer to Frame 45.
2. Isolate the mains cold water supply to the
boiler.
3. Drain the boiler DHW circuit. Refer to Frame
60.
4. Remove the DHW flow turbine cartridge.
Refer to Frame 69.
5. Unscrew the flow regulator housing.
6. Inspect the flow regulator for any blockage
and remove if necessary.
7. Reassemble in reverse order.
8. Refill the boiler. Refer to Frame 22.
9. Check Operation of the boiler. Refer to
Frame 36.

Servicing

71 NO FLOW Thermistor Replacement
1. Refer to Frame 45.
2. Drain down the boiler. Refer to Frame 60.
3. Unplug the electrical lead.
4. Unscrew the thermistor (to facilitate removal a
13mm socket spanner should be used).
5. Fit the new thermistor using the sealing washer
provided.
6. Reassemble in the reverse order.
7. Refill the boiler. Refer to Frame 22.
8. Check the operation of the boiler. Refer to Frame
36.
3

Keston Combi - Installation and Servicing

SERVICING
72 heat engine reNEWAL
Refer also to Frame 6 - ‘Boiler Exploded View’
IMPORTANT
Before starting the removal procedure, protect the gas and electrical controls with a waterproof sheet or plastic bag.
1. Refer to Frame 45.
2. Drain the boiler. Refer to Frame 60.
3. Remove the fan / venturi assembly and place on one side.
Refer to frame 46.

12. Undo the inlet pipe union nut and remove the retaining spring
clip and remove pipe.
13. Undo the flow pipe union nut and remove pipe.
14. Remove the condensate rubber pipe. Refer to Frame 56, no. 2.

4. Remove the burner and place on one side. Refer to Frame 15. Remove the two heat exchanger fixing screws.
48.
16. Remove the Heat exchanger.
5. Remove the ignition and detection electrodes and diverter 17. Reassemble in reverse order, ensuring the heat exchanger
actuator head. Refer to Frames 51, 52 and 55.
LH retaining bracket is correctly positioned. Replace any
6. Remove the spark generator. Refer to Frame 53.

9. Remove the expansion vessel. Refer to Frame 73.

new ‘o’ rings supplied with new heat exchanger and replacing
gaskets or seals if any sign of damage is evident. When
replacing the spring clips located on both the flow and return
pipe connections, ensure clip is oriented to correctly match
connecting pipe diameters.

10. Remove the no flow thermistor. Refer to Frame 71.

18. Ensure the trap/siphon is filled with water. Refer to Frame 56.

7. Disconnect flue thermostat.
8. Remove the gas valve. Refer to Frame 54.

servicing

11. Remove the 2 M5 screws retaining the gas valve mounting 19. Refill the boiler. Refer to Frame 22.
bracket and transfer bracket to the new heat exchanger.
20. Check operation of the boiler. Refer to Frame 36.

Keston Combi - Installation and Servicing

SERVICING
73 expansion vessel recharging & replacement
RECHARGING

Recharge
Point

1. Refer to Frame 45.
2. Remove the charge point cover.
3. Recharge the tank pressure to 0.75 bar.

4. Re-assemble in reverse order
5. Check operation of the boiler. Refer to Frame36.
REPLACEMENT
6. Refer to Frame 45.
7. Drain the boiler CH circuit. Refer to Frame 60.
8. Unscrew the union nut on the vessel water
connection pipe.

Servicing

9. Support the expansion vessel and unscrew the 2
screws from the securing clamp, located on the top
of the boiler, and remove. (Note the position of the
bracket on the vessel)

10. Remove the expansion vessel.
11. Fit the new expansion vessel.
12. Reassemble in reverse order.
13. Refill the boiler. Refer to Frame 22.
14. Check operation of the boiler. Refer to Frame 36.

74 Boiler sealing panel seal replacement
1. Refer to Frame 45.
2. Remove the old seal from the casing and
thoroughly clean the casing surfaces.
3. Fit the new seal, ensuring the bottom joint
provides an air tight seal.
5. Reassemble in reverse order.
6. Check operation of the boiler. Refer to
Frame 36.
Note. Ensure that the boiler front panel is
correctly sealed, compressing the seal
to make an airtight joint.

Keston Combi - Installation and Servicing

Fault finding
Note. Boiler status display information is shown in shaded boxes below. Up to six messages will be displayed in rotation.

Overheat lockout

1 Fill system to 1.0 bar

2 Bleed radiators

3 Check radiator valves open

4 Reset boiler

5 Contact installer

Ignition lockout /
Flue Overheat

Go to Frame 76
Flow Temperature Overheat Lockout

1 Check other gas appliances work

2 Reset boiler

3 Contact Installer

Go to Frame 77
Ignition Lockout

Too many resets

Contact installer

5 Resets with 15 minutes
Turn power off and on

Fault 8

Contact installer

Go to Frame 78
False Flame Lockout

Low water pressure

1 Fill system to 1.0 bar

Flame loss

2 Bleed radiators

1 Check other gas appliances

3 Contact installer

2 contact installer

Go to Frame 79
Low Water Pressure
Go to Frame 80
Flame Loss

Fan fault

Contact installer

Go to Frame 81
Fan Fault

Return thermistor fault

Contact installer

Go to Frame 82
Return Thermistor Fault

Outside sensor fault

Contact installer

Go to Frame 83
Outside sensor fault

Low mains voltage

Contact electricity provider

Low mains voltage
Contact Electricity Provider

PCB Fault

Contact installer

If PCB is a spare check Boiler Chip Card
(BCC) fitted otherwise replace PCB

PCB Replaced

Reset boiler

Reset the boiler

Flow thermistor fault

Contact installer

Go to Frame 82
Return Thermistor Fault

Boiler Chip Card Fault

Contact installer

Go to Frame 85
BCC Fault

12 month service interval request

Contact installer

It is recommended to have the boiler serviced
Reset the boiler to clear message

No CH operation but DHW operates OK

Go to Frame 86
No CH operation but DHW works OK

No DHW operation but CH operates OK

Go to Frame 87
No DHW but CH operates OK

No Display

Go to Frame 88
No Display

RESET PROCEDURE - To reset boiler, turn mode knob to reset position and immediately turn knob back to required setting.

Keston Combi - Installation and Servicing

FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING

75 fault finding chart MAIN MENU

FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING

Fault finding
76 Overheat lockout - 1 fill system to 1.0 bar - 2 bleed radiators
3 check radiator valves open - 4 reset boiler - 5 contact installer
Is the Boiler and CH System filled with water and all
isolation and radiator valves open?

Fill and vent the system and open all
isolation valves, then reset boiler

yes

Check that the Pump is rotating freely. Is
the Differential now below 20°C?

yes
Is the Flow/Return Differential across the Boiler in
excess of 30°C?
NO

Check the Return Thermistor (Refer to Frame 49)
Check resistance using a suitable multimeter
connected across the thermistor’s terminal pins
At 25 oC expect

9,700 - 10,300

At 60 C expect

2,400 - 2,600

Ohms

At 85 oC expect

1,000 - 1,100

Ohms

yes

Replace the Pump,
then reset boiler

OK, now
reset boiler

Ohms
RESET PROCEDURE - To reset boiler, turn mode knob to reset
position and immediately turn knob back to required setting.

77 Ignition lockout / FLUE OVERHEAT - 1 check other gas appliances work

- 2 reset boiler - 3 contact installer
If the boiler is reset does the boiler ignite no
for a short time and then extinguish?
yes

Check gas supply and
rectify fault

yes

Check the detection electrode and
associated harness for: continuity,
visual condition and position (Refer to
Frame 52). Check if the condensate
pipe is blocked. Replace as necessary

Check ignition electrode and associated
harness for: continuity, visual condition
yes
and position. (Refer to Frame 51) Are
these functioning correctly?
yes

Is the Gas Pressure available at
the Boiler Inlet (>18 mbar)?

Check siphon and condensate drain
pipe work for blockage and rectify if
necessary. Boiler now working OK?

Is approx 215Vdc supply available
at the Gas Valve? (* See note)

yes
Unplug gas valve. Is resistance
between outside pins 4KΩ (±2)?

Check wiring connection
from gas valve to PCB for
continuity. If the wiring is
OK then replace the PCB
Replace Gas Valve

yes
Check spark generator and associated
harness for: continuity and visual
condition. (Refer to Frame 53) Are
these functioning correctly?

Replace Spark
Generator and harness
as necessary

Replace Ignition Electrode and
associated harness as necessary

No
Check flue for obstruction

yes

Clear obstruction

yes

Ensure wiring correctly
connected

No
Check wiring to thermostat
No
Check flue temperature always
remains below 90ºC

yes

Replace Thermostat

No
Check if burner is damaged
No
Replace heat exchanger

yes

Replace burner

* Note: due to the wave form of
the rectified voltage, the reading
will vary depending on the type
of meter used to measure the
value. In general terms a reading
greater than 150V indicates that
the correct voltage is supplied to
the gas valve.
RESET PROCEDURE - To reset
boiler, turn mode knob to reset
position and immediately turn
knob back to required setting.

Keston Combi - Installation and Servicing

Fault finding

Reset the boiler, does Boiler Work OK?

YES

NO
Separate the flame detection electrode in-line
connector. Is there continuity between the terminals
pins connected to the electrode?

yes

Check routing and integrity of internal boiler
wiring is OK. Check condition of Flame Sense
Electrode and replace if deteriorated.

Replace Flame Detection Electrode

NO
Check routing and integrity of internal boiler wiring.

RESET PROCEDURE - To reset boiler, turn mode knob to reset position and immediately turn knob back to required setting.

79 LOW WATER PRESSURE - 1 FILL SYSTEM TO 1.0 BAR
3 CONTACT INSTALLER

Are the Boiler and CH System filled with water and
all isolation and radiator valves open (check pressure
gauge is between 1 to 1.5 bar)?

2 BLEED RADIATORS -

Fill and vent the system and open all isolation valves

YES
Are connections on water pressure sensor secure?

Re-fit connections

YES
Replace water pressure sensor

Keston Combi - Installation and Servicing

FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING

78 FAULT 8 - CONTACT INSTALLER (False Flame Lockout)

FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING

Fault finding
80 FLAME LOSS - 1 CHECK OTHER GAS APPLIANCES WORK
2 CONTACT INSTALLER
Does the boiler ignite for a short
time and then extinguish?
yes
Check the detection electrode and
associated harness for: continuity,
visual condition and position (Refer
to Frame 52). Check if condensate
pipe is blocked. Check if flue is
blocked.
Replace as necessary

Is the Gas Pressure available at
the Boiler Inlet (18 mbar)?

Check gas supply and
rectify fault

yes
Is 215Vdc supply available at the
Gas Valve while the flame is on?
(* See note)

Check wiring from gas
valve to PCB for continuity.
If the wiring is OK then
replace the PCB

yes
Check spark generator and
associated harness for: continuity
and visual condition. (Refer to
Frame 53) Are these functioning
correctly?

Replace Spark Generator
and Harness as necessary.

yes
Check ignition electrode and
associated harness for: continuity,
visual condition and position.
(Refer to Frame 51) Are these
functioning correctly?

Replace Ignition
Electrode and
associated harness as
necessary

yes
Check siphon and condensate
drain pipe work for blockage and
rectify if necessary. Boiler now
working OK?

Replace Gas Valve

No
Check flue for obstruction

yes

Clear obstruction

no
Check wiring to thermostat

yes

Ensure wiring correctly
connected

no
Check flue temperature always
remains below 90ºC

yes

Replace Thermostat

no
Check if burner is
damaged

yes

Replace burner

no
Replace heat exchanger
* Note: due to the wave form of the rectified voltage, the reading will vary depending on the type of meter used to measure the
value. In general terms a reading greater than 150V indicates that the correct voltage is supplied to the gas valve.

Keston Combi - Installation and Servicing

Fault finding

Does the wiring from the Fan to the PCB have
secure connections at both ends and has not
deteriorated? Does the wiring have continuity?
yes
Is there 230Vac at the Blue and Brown connections
to the 3 way connection on the Fan?

Rectify Wiring &
connections

Replace PCB

FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING

81 FAN FAULT - CONTACT INSTALLER

YES
Replace Fan

82 RETURN THERMISTOR FAULT - CONTACT INSTALLER
Remove the Return Thermistor from the CH Return
Pipe and disconnect the wires.
Check the resistance using a suitable multimeter
connected across the thermistor’s terminal pins.
At 25 oC expect

9,700 - 10,300

At 60 C expect

2,400 - 2,600

Ohms

At 85 oC expect

1,000 - 1,100

Ohms

Fit a new Thermistor

Ohms

Is the Thermistor value correct?

Check and replace wiring as necessary

yes
Is there continuity between the PCB and the Thermistor?
yes

Replace PCB

83 OUTSIDE SENSOR FAULT - CONTACT INSTALLER

Is the wiring securely connected at both the boiler and
Outside Sensor?

Securely connect the wiring at both the
boiler and Outside Sensor

yes
Disconnect the wires to the outside sensor.
Check the resistance using a suitable multimeter
connected across the Outside Sensor’s terminal pins.
At 0 oC

expect

31,000 - 35,000

At 15 oC expect

15,000 - 16,500

Ohms

At 30 oC expect

7,700 - 8,500

Ohms

Fit a new Outside Sensor

Is the Outside Sensor value correct?
yes
Is the wiring securely connected between the
incoming terminal block boiler connection of the
Outside Sensor and the PCB?

Keston Combi - Installation and Servicing

yes

Securely connect the wiring at the
Terminal Block and the PCB

Replace PCB

FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING

Fault finding
84 FLOW THERMISTOR FAULT - CONTACT INSTALLER
no

Is the wiring securely connected to the Flow Thermistor
(located in the top of the Heat Exchanger?)
yes

Disconnect the wiring from the Flow Thermistor
Check the resistance using a suitable multimeter connected
across the Thermistor’s terminal pins.
At 25 oC expect

9,700 - 10,300

Ohms

At 60 oC expect

2,400 - 2,600

Ohms

At 85 oC expect

1,000 - 1,100

Ohms

YES

Securely connect the wiring to the Flow
Thermistor

Fit a new Thermistor

Is the wiring securely connected to the low
voltage 6 way connector at the front left hand
side of the PCB?
yes

Is the Thermistor value correct?

Replace PCB

NO
Securely connect the
wiring to the PCB

85 BOILER CHIP CARD FAULT - CONTACT INSTALLER
Is the correct BCC for the boiler securely inserted into the
slot at the front left of the PCB?
(identified by the label on the BCC)

Securely attach the BCC for the boiler onto
the PCB and after switching power on and ‘c0’
being shown, reset the boiler.
Note. Ensure the correct orientation of BCC by
placing “TOP” side up.

yes
Replace the BCC with a new BCC (that is correct for the
boiler). After switching power on and ‘c0’ being shown,
reset the boiler. Is ‘c2’ still shown?

YES

Replace PCB

RESET PROCEDURE - To reset boiler, turn mode knob to reset position and immediately turn knob back to required setting.

86 nO ch oPERATION BUT dhw WORKS ok
no

Is the mode knob in the Winter position?
yes
Are the Timer and the Room Thermostat switched on?

Move the mode knob to the Winter position

Switch the Timer and Room Thermostat On

Open the Radiator Valves

yes
Are the Radiator Valves Open?
yes
Is there 230Vac at (A)?
yes
Replace the
Diverter Valve

NO
There is no Voltage from the
Timer/Room Stat. This is not
boiler fault. Ensure Voltage
is supplied to boiler by
rectifying external wiring.
A

Keston Combi - Installation and Servicing

Fault finding
87 nO HW BUT CH ON
no

yes
Are the flow rates correct as per Frame 2.

yes
Is the wiring between the PCB and the diverter no
valve motor connected?
yes
Check diverter head fully engaged and clip
secured onto waterset.

yes
no

Is diverter stuck in the CH position

Is the red neon
illuminated on the turbine
sensor?
Adjust flow rates to achieve 35º
temp rise and check filter fitted in
turbine is not blocked with debris.
Reconnect wiring or
replace wiring harness if
no continuity.
Re-engage diverter
head and secure clip to
wateset
Replace PCB

yes

YES Is hot and cold
pipework crossed?
NO

FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING

Does the display show “hot water” “temperature XXºC” - “high efficiency”?

NO
Replace PCB

Is the wiring connected
between PCB and DHW
sensor?

YES
Remove the turbine, and
check for debris in the
turbine & filter. Replace
turbine if necessary. Is
DHW OK?
NO

Check and replace diverter valve motor head.
Is Boiler DHW OK?

Replace turbine sensor

NO
Change diverter Valve cartridge - rear section

Re-connect wiring

88 No Display
Is there 230Vac to the boiler at L and N?

Supply power to the boiler

Connect the wiring from the terminal block to the
Main PCB securely.

Connect the ribbon from the main PCB to the User
Interface PCB securely

yes
Is the wiring from the terminal block to the Main PCB
connected securely?
yes
Is the ribbon cable from the main PCB to the User
Interface PCB connected securely?
yes
Is ribbon cable damaged?

yes

Replace the
User Interface
PCB

Replace ribbon cable

L
N

Keston Combi - Installation and Servicing

SPARE parts
When replacing any part on this appliance use only spare parts that you can be assured conform to the safety and performance
specification that we require. Do not use reconditioned or copy parts that have not been clearly authorised by Keston. Failure to do so
could affect safety or performance of this appliance.

Our Parts team are also available to help with your Keston Spare Parts enquiries on 01482 498665.
When calling, and to ensure we can provide you with the most accurate parts information, please ensure you have the following to
hand;
-

Boiler Model

Appliance GC Number

Boiler Serial Number

Keston Combi - Installation and Servicing

Benchmark Commissioning and
Servicing Section
It is a requirement that the boiler is installed and commissioned to the
manufacturers instructions and the data fields on the commissioning checklist
completed in full.
To instigate the boiler guarantee the boiler needs to be registered with the
manufacturer within one month of the installation.
To maintain the boiler guarantee it is essential that the boiler is serviced annually
by a Gas Safe registered engineer who has been trained on the boiler installed.
The service details should be recorded on the Benchmark Service Interval
Record and left with the householder.

GAS BOILER SYSTEM COMMISSIONING CHECKLIST
This Commissioning Checklist is to be completed in full by the competent person who commissioned the boiler as a means of demonstrating
compliance with the appropriate Building Regulations and then handed to the customer to keep for future reference.

CONTROLS
Programmable room thermostat
Optimum start control
Combination Boiler
Fitted
Fitted
Fitted
Automatic bypass to system

Fitted

Boiler interlock
ALL SYSTEMS
Yes

Yes
CENTRAL HEATING MODE
OR
mbar

mbar

Central heating return temperature
COMBINATION BOILERS ONLY
Yes
Yes
DOMESTIC HOT WATER MODE
OR
mbar OR

mbar

Cold water inlet temperature
Yes

Temperature

CONDENSING BOILERS ONLY
Yes
ALL INSTALLATIONS
AND

Ratio

AND

Ratio
Yes
Yes
Yes
Yes

* Allinstallations in England and Wales must be
to Local Authority Building Control (LABC) either directly or through a
Competent Persons Scheme. A Building Regulations Compliance
will then be issued to the customer.
www.centralheating.co.uk

SERVICE RECORD
It is recommended that your heating system is serviced regularly and that the appropriate Service Interval Record is completed.
Service Provider

SERVICE 01

SERVICE 02

AND
(Where Possible)

AND

²%
²%

(Where Possible)

Signature

SERVICE 03

SERVICE 04

AND
(Where Possible)

AND

²%
²%

(Where Possible)

Signature

SERVICE 05

SERVICE 06

AND
(Where Possible)

AND

(Where Possible)

Signature

SERVICE 07

SERVICE 08

AND
AND

(Where Possible)

Signature

SERVICE 09

SERVICE 10

AND

Signature

AND

²%
²%

Signature

(Where Possible)

AND

²%
²%

Signature

(Where Possible)

AND

²%
²%

AND

AND
(Where Possible)

AND

²%
²%

Signature

www.centralheating.co.uk

FLOWCHART FOR CO LEVEL AND COMBUSTION RATIO
CHECK ON COMMISSIONING A CONDENSING BOILER

Important Preliminary Information on Checks
The air gas ratio valve is factory-set and must not be adjusted DURING COMMISSIONING.
If the boiler requires conversion to operate with a different gas family (e.g. conversion from natural gas to LPG) separate guidance is provided with the conversion kit supplied and this must be followed.
PRIOR TO CO LEVEL AND COMBUSTION RATIO CHECK
The installation instructions must have been followed, gas type verified and gas supply pressure / gas rate checked as
required prior to commissioning.
As part of the installation process, ESPECIALLY WHERE A FLUE HAS BEEN FITTED BY PERSONS OTHER THAN
THE BOILER INSTALLER, visually check the integrity of the whole flue system to confirm that all components are
correctly assembled, fixed and supported. Check that maximum flue lengths have not been exceeded and all guidance
has been followed (e.g. Gas Safe Register Technical Bulletin (TB) 008 where chimney/flues are in voids).
The ECGA should be of the correct type, as specified by BS 7967.
Prior to its use, the ECGA should have been maintained and calibrated as specified by the manufacturer. The installer
must have the relevant competence for use of the analyser.
Check and zero the analyser IN FRESH AIR in accordance with the analyser manufacturer’s instructions.

KEY:
CO = carbon monoxide
CO2 = carbon dioxide
O2 = oxygen
Combustion Ratio = The CO reading measured in ppm divided by the CO2 reading first converted to ppm
ppm = parts per million
GS(I&U)R = Gas Safety (Installation and Use) Regulations

*Setting to Minimum Rate:
1. Turn the CH temperature control knob into the 10 O’clock position.
2. Create a CH demand by ensuring that the system controls are requesting heat and the boiler Mode
Knob is in the Winter Position.
3. Within an overall time of 3 seconds, turn the CH temperature control knob fully clockwise, back to
10 O’clock and then fully clockwise again.
4. The following messages will be shown in rotation on the display:
“Service Mode”
“Minimum Output”
“Move CH Knob to End”
and the boiler output will be reduced to minimum.
5. The boiler will remain at minimum rate for 5 minutes before reverting to normal operation.

Keston Combi - Installation and Servicing

Start

Set Boiler to Maximum Gas Rate
In accordance with boiler instructions,
set boiler to operate at maximum rate
(full load condition). Allow sufficient
time for combustion to stabilise.
Note. Do not insert analyser probe
during this period to avoid possible
flooding of sensor.

Carry Out Flue Integrity Check Using Analyser
Insert analyser probe into air inlet test point (where available) and allow
readings to stabilise.
Note. Where no air inlet test point is provided then a flue integrity check with
the analyser is not possible. The installer should verify that flue integrity has
been visually checked in accordance with the “Prior to CO level and
combustion ratio check” (see opposite page) before proceeding to the
“check CO level and combustion ratio at maximum rate” stage below.

Verify Flue Integrity
Analyser readings indicate that combustion products and inlet air
must be mixing. Further investigation of the flue is therefore required.
Check that flue components are assembled, fixed and supported as
per instructions. Check that flue and flue terminal are not obstructed.

Is
O2 more than or
equal to 20.6% OR CO2
less than or equal to
0.2%?

Yes
Is
O2 more than or
equal to 20.6% OR CO2
less than or equal to
0.2%?

Check CO level and Combustion Ratio
at Maximum Gas Rate

Yes

With boiler still set at maximum gas rate,
insert analyser probe into flue gas
sampling point. Allow readings to stabilise
before recording.

No
Turn off appliance and call Ideal Technical Helpline for advice
The appliance must not be commissioned until problems are identified
and resolved. If commissioning cannot be fully completed, the appliance
must be disconnected from the gas supply in accordance with GSIUR.

Yes

Check that no seals, e.g. Those on flue extensions, have
been displaced during installation. Rectify if necessary.

Is
CO level less
than 350ppm AND CO/CO2
ratio less than
0.0040?

Set Boiler to Minimum Gas Rate
(*see opposite page)
In accordance with boiler instructions, set boiler to
operate at minimum rate (to minimum load condition).
Allow sufficient time for combustion to stabilise.

Yes

Check CO and Combustion Ratio at Minimum Gas Rate
With boiler set at minimum rate, insert analyser probe into flue
gas sampling point. Allow readings to stabilise before recording.

No
Turn off Appliance and Call Ideal Technical Helpline
The appliance must not be commissioned until problems
are identified and resolved. If commissioning cannot be
fully completed, the appliance must be disconnected from
the gas supply in accordance with GS(I&U)R. NOTE:
Check and record CO level and combustion ratio at both
maximum AND minimum rate before contacting Ideal.

Is
CO level less
than 350ppm AND CO/CO2
ratio less than
0.0040?
Yes

Boiler is Operating Satisfactorily
No further actions required.
Ensure test points are capped, boiler case is correctly replaced and all
other commissioning procedures are completed. Complete Benchmark
Checklist, recording CO and combustion ratio readings as required.

Keston Combi - Installation and Servicing

Keston Heating, PO Box 103, National Avenue, Kingston Upon Hull, HU5 4JN
Tel. +44 (0) 1482 443005 Fax. +44 (0) 1482 467133.
www.keston.co.uk

February 2014

UIN 207895 A03

Keston pursues a policy of continuing improvement
in the design and performance of its products.
The right is therefore reserved to vary specification without notice.

Source Exif Data:

File Type                       : PDF
File Type Extension             : pdf
MIME Type                       : application/pdf
PDF Version                     : 1.6
Linearized                      : Yes
Create Date                     : 2014:02:12 10:21:05Z
Creator                         : Adobe InDesign CS6 (Windows)
Modify Date                     : 2014:02:12 10:33:37Z
XMP Toolkit                     : Adobe XMP Core 5.2-c001 63.139439, 2010/09/27-13:37:26
Metadata Date                   : 2014:02:12 10:33:37Z
Creator Tool                    : Adobe InDesign CS6 (Windows)
Instance ID                     : uuid:646f5e1b-9edf-44bb-b97f-f3d452f30f13
Original Document ID            : xmp.did:0FD61563DEE0DF119B0BC19533DBCE45
Document ID                     : xmp.id:CE68DBDFC893E311B503B0D655ED5B3C
Rendition Class                 : proof:pdf
Derived From Instance ID        : xmp.iid:6600DDA9F28FE311A714A471F059E62D
Derived From Document ID        : xmp.did:8DEFE4B3E48FE311A714A471F059E62D
Derived From Original Document ID: xmp.did:0FD61563DEE0DF119B0BC19533DBCE45
Derived From Rendition Class    : default
History Action                  : converted
History Parameters              : from application/x-indesign to application/pdf
History Software Agent          : Adobe InDesign CS6 (Windows)
History Changed                 : /
History When                    : 2014:02:12 10:21:17Z
Format                          : application/pdf
Producer                        : Adobe PDF Library 10.0.1
Trapped                         : False
Page Count                      : 72

EXIF Metadata provided by EXIF.tools

Keston Combi 35Kw Users Manual

keston combi manual keston combi manual

Navigation menu

Versions of this User Manual:

Views

Navigation