BOSCH Water Heater, Gas Manual L0803440

User Manual: BOSCH BOSCH Water heater, Gas Manual BOSCH Water heater, Gas Owner's Manual, BOSCH Water heater, Gas installation guides

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BOSCH

MODEL

125BO LP and 125BO NG - OUTDOOR

MODEL

For exterior use only
Piezo Ignition
Suitable for heating potable water only
Not approved for space heating purposes

AQ 125 BO NG - Natural Gas
AQ 125 BO LP - Liquefied Petroleum

-J

Warning:
If the information in this manual is not
followed exactly, a fire or explosion may result
causing property damage, personal injury or death.
Do not store or use gasoline or other flammable
vapor and liquids in the vicinity of this or any other
appliance.
Improper installation, adjustment, alteration, service
or maintenance
can cause injury or property
damage. Refer to this manual. For assistance or
additional information consult a qualified installer,
service agency or the gas supplier.
In the Commonwealth
of Massachusetts
this

o
CO

product
is approved
only for seasonal
use.
Installation
must be performed
by a licensed
plumber or gas fitter.
Upon
completion
of
the
installation,
these
instructions should be handed to the user of the

appliance
oo

for future reference.

(LP) Gas

What

to do if you smell gas

•

Close gas valve.

•

Do not try to light any appliance.

•

Do not touch

any electrical

switch;

do not use any

phone in your building.
•

If you cannot
department.

reach your gas supplier,

calI the fire

•

Immediately calI your gas supplier from a neighbor's
phone. Follow the gas supplier's instructions

•

Installation and service must be performed
by a
qualified installer, service agency or the gas supplier.

Index

Warning

2
2.1

Appliance
Features

2.2

AQ125

2.3

Unpacking

2.4
2.5

General rules to follow for safe operation
Dimensions and installation clearances

5
6

Installation

3.1

Introduction

3.2

Proper location

3.3

Heater placement

3.4

Mounting

3.5

Gas piping

3.6
3.7

Measuring gas pressure
Water connections

12
12

3.8

Electrical

Operation

4.1

For your safety read before operating
heater

details

Warning

4
4

BO specifications

(Technical

the AQ-1 25-BO

data)

heater

4
5

instructions

7
for installing

your heater

and clearances

7
8

installation

& connections

connections

instructions

Featuring
Piezo Ignition

your water
14

4.2

Lighting

For your safety

4.3

To turn off appliance

4.4

Setting

Do not store or use gasoline or other flammable,
combustible or corrosive vapors and liquids in the
vicinity of this or any other appliance,

Maintenance

5.1

Maintenance

5.2

Water

5.3
5.4

Pilot
Main burners

16
16

5.5

Vent assembly

5.6

Mineral

6
6.1

Troubleshooting
Introduction

17
17

6.2
6.3

Pilot will not light
Pilot will light but not stay on when button released

17
17

6.4

Burner do not ignite with water flow

6.5
6.6

Hot water temp fluctuates
Water is too hot

17
18

6.7

Water

Interior

7.1

Interior

7.2
7.3

Components
Parts list

Protecting the environment

Twelve Year Limited Warranty

instructions
the water temperature

and service

intervals

valve

scale build-up

from hot to cold

is not hot enough

components

and diagram

components
diagram

parts list

19
19
20
21

8 716 473 147

Warning

What

to do if you smell gas

•

Close gas valve.

•

Do not try to light any appliance.

•

Do not touch any electrical
phone in your building.

•

Immediately call your gas supplier from a neighbor's
phone. Follow the gas supplier's instructions.

•

If you cannot
department.

•

Installation and service must be performed
by a
qualified installer, service agency or the gas supplier.

switch;

do not use any

reach your gas supplier,

call the fire
_k
LL_ Vapors from flammable
liquids will explode and
catch fire causing death
or severe bums.
Do not use or store flammable
=roducts such as gasoline,
solvents or adhesives in the
same room or area near the
water heater.
Keep flammable products:
1. far away from heater,
2. in approved containers,
3. tightly closed and
4. out of children's reach.

Water heater has a main
burner:
1. which may come on
any time and
2. will ignite flammable
vapors.
Vapors:
1, cannot be seen_
2, are heavier than air,
3, go a long way on the floor and
4, can be carried from other
rooms to the pilot flame by
air currents.

Installation:

area at least 18" above the

Do not install water heater
where flammable
products will
be stored or used unless the
main burner and pilot flames

floor. This will reduce, but not
eliminate, the risk of vapors
being ignited by the main
burner or pilot flame.

Read and follow water heater warnings and instructions.
If owners manuals is missing, contact the retailer or manufacturer.

Fig.

Water temperature over 125 F can
cause severe burns instantly or
death from scalds.
Children, disabled and elderly are
at highest risk of being scalded.
See instruction manual before
setting temperature at water
heater.
Feel water before bathing or
showering.
Temperature limiting valves are
available, see manual.

Fig. 1

8 716 473 147

Appliance details

Appliance

2,1

Features

details
•

Cold water connection

Burner output proportional to hot water flow demand
for maximum energy efficiency

•

Water valve material:
Sulfid)

Stainless

•

Minimum water flow: 0.5 gallon/minute

•

Minimum recommended
(2.07 bar)

Adjustable water flow restrictor to ensure that water
flow demand will not exceed the heating capacity of
the heater

•

Connections:

•

Safety thermocouple

Dimensions

•

Automatic

•

Copper

•

Easily removable

•

Easy one person installation

•

Easy Pilot
ignition.

steel burners with stabilized

Built-in corrosion

blue flame

resistant draft diverter

at pilot burner

overheating

protection

heating coils for endless
one-piece

Flame

Ignition

shut-off

sensor

supply of hot water

cover

with

push

button

piezo

BOSCH
is constantly
improving
its
products,
therefore
specifications
are
subject to change without prior notice.

2,2

AQ125

BO specifications

(Technical
Approved

data)

Maximum flow
(25°C) rise.

rate: 3.7

GPM

(14

I/min)

water

(1.9 I/m)

pressure:

PSI

Bottom of heater

Depth (in): 10.5" (265 mm)

•

Width

•

Height (in): 36.75"

•

Weight:

(in): 18.25"

(460 mm)

64 pounds

(936 mm)
(29 kg).

Gas types
Natural Gas.
LP Gas
Safety

devices

•

Flame failure device (ionization

•

Pressure relief valve (supplied

•

Over heat prevention

flame rod sensor)
with heater)

(temperature

limiter).

resistant

IP X5 (protection

Capacity

Polymer (PPS) (Polypropylene

•

Water

in US/Canada

(inches) - 1/2"

against water drops).

at a 45°F

Maximum output
101,772 Btu/h (29.8 kW)
Maximum input
117,000 Btu/h (34.3 kW)
Efficiency in %
Recovery efficiency 80%
Min. Output
28,000 Btu/h (8.2 kW)
Gas Requirement
Gas connection
Inlet gas pressure

(inches) - 3/4"
under maximum operation*

•

Propane:

10.5" - 14" water column

•

Natural Gas: 5.7" - 14" water column.

* To measure Gas Pressure,
Pressure, chapter 3.6.

see

Measuring

Gas

Water
•

Hot water connection

(inches) - 1/2"

8 716 473 147

Appliance details

2.3

Unpacking

the AQ-125-BO

heater

2.4

This heater is packed securely.
Before installing the unit, be certain you have the
correct heater for your type of Gas - Propane or
Natural Gas. Identification labels are found on the

•

shipping box, and on the rating plate which is located on
the right side panel of the cover.
The box includes:

• Heat shield
Mounting

•

Product

•

Installation

card

•

3. The appliance must be isolated from the gas
supply piping system by closing its individual manual
gas shutoff valve (not supplied with heater) during
any pressure testing at pressures in excess of 1/2Psig
(3.5 kPa).

Do not lose this manual, there is a charge for a
replacement,
Please complete and return the enclosed product
registration card.

The appliance and its gas connection
must be leak
tested before placing the appliance in operation.
•

4. Keep water heater area clear and free from
combustibles
and flammable liquids. Do not locate
the heater over any material which might burn.

•

5. Correct gas pressure is critical for the optimum
operation of this heater. Gas piping must be sized to
provide the required pressure at the maximum output
of the heater, while all the other gas appliances are in
operation. Check with your local gas supplier, and
see the section on connecting the gas supply.

•

6. Should overheating occur or the gas supply fail to
shut off, turn off the gas supply at the manual gas
shut off valve, on the gas line. Note: manual gas
shutoff valve is not supplied with the heater.

•

7. Do not use this appliance if any part has been
underwater.
Immediately
call a qualified
service
technician to inspect the appliance and to replace
any part of the control system and any gas control
which has been underwater.

The AQ125 BO is not approved or designed for:

• Heating or other recirculating/pumping

applications*

• Solar/preheat backup or high temperature booster
use
* This includes domestic hot water circulator pump loop
systems that may previously exist in a home hot water
system. The use of a small electric mini-tank (4-6 gallon
size) should be used for this application; when
designed so the pump will circulate the hot water in the
mini-tank only and through the building's hot water
return loop (timed or thermostatic controlled operation
of the pump is commonly done). The AQ125 BO should
be plumbed in line before the mini-tank water heater,
contact BBTNA if further instruction is needed.

8 716 473 147

and /or

2. Carefully plan where you install the heater. Proper
clearances must be followed.

manual.

• Manufactured (mobile) homes, RV's or boats

CODES

•

screws
registration

for safe

1. You should follow these instructions
when you
install your heater.
In the United States:
The
installation must conform with local codes or, in the
absence of local codes, the National Fuel Gas Code
ANSI Z223.1/NFPA
54.
In Canada: The Installation
should conform
with
CGA B149.(1,2)
INSTALLATION
local installation codes.

• Pressure relief valve

•

General rules to follow
operation

Appliance details

2,5

Dimensions

and installation

clearances
10_½ "

18"

_0
03

WATER

INLET

WATER

OUTLET

GAS

INLET

AQ125B

Fig. 3

10.JS

Dimensions

Fig, 4

Minimum

clearances

3ft.
4 ft.
0"

4 ft.
1 ft.

Table 1 Minimum

clearances

8 716 473 147

Installation

3.1

Introduction

Please

instructions

these

instructions

instructions.

Failure

may result in:

•

Damage or injury.

•

Improper

•

Loss of warranty.

operation.

Please contact

3,2

instructions

BBT North America with any questions.

Proper location
heater

for installing

your

Carefully select the location of the water heater.
Follow the guidelines below:
•

1, Locate the heater where an adequate gas line size
and
plumbing
connections
are
feasible
and
convenient,

•

2, The hot water lines should be kept short to save
energy. Centrally locating the water heater is best. It
is always best to have hot water lines insulated to
prevent the possibility of any freeze damage.

•

3. The water in this heater is cold
cold except for the times that hot
The heater is equipped
with
equipment that will operate and
the water in the heater to 5°F

and always remains
water is being used.
freeze prevention
prevent freezing of
with no wind chill,

Electrical power must be maintained
allow this to function,

8 716 473 147

to the heater to

Installation

3.3

instructions

Heater

placement

and clearances

3.4

Mounting

installation

The AQ125
BO is design certified
for installation
directly on a combustible
wall. (see 3.4 Mounting
installation). For installation on vinyl siding see Fig. 7.
Keep the area below the heater free of combustible
material.
Minimum

clearances

If the appliance is installed under an overhang, there
must be a 36" clearance from the top of the appliance
and the mounting area must be open in front and on the
sides of the appliance.

Front cover should be removed in order to
inspect
components
instructions below).

visually

(see

To remove front cover.
•

Loosen the two screws

located

on the sides of the

front panel, see Fig. 6.

AQ125BO_6

Fig. 5

ill

!iiii

i ¸_ _ _

_i _

__;_

_ ¸

;i;

Fig. 6

Directly

opening; operable windows,
doors and any fresh air
openings

> 4 ft

From any adjacent
shruberry

> 4 ft

Below a gutter, sanitary
pipework, eaves or overhang

> 3 ft

Above ground

> 1 ft

From a gas meter, gas
regulator, electrical box or
another 125 BO heater.

> 3 ft

front cover

•

Ensure that the flue
combustible
material.

•

After inspection,
screws.

•

Install only on an external wall, as close as possible
to the most frequently used hot tap (note clearances
in chapter 3.3).

•

If the unit is to be installed on a combustible

below or from an

wall or tall

Remove

use the enclosed

terminal

clear

any

replace front cover and tighten

surface

heat shield (see Fig. 5).

Table 2 Clearances

8 716 473 147

Installation

instructions

Vinyl

siding

Vinyl
siding

Fig. 7
•

Secure heater to wall using enclosed
mounting
screws, Use mounting template for proper screw
location.

•

Locate head of screw
mounting bracket.

in the key hole of the top

Vent Safety System
The AQ125 BO will shut down if the intake or exhaust
louvers on the vent cap are blocked for any reason; see
troubleshooting section on page 17.

8 716 473 147

Installation

3.5

instructions

Gas piping & connections

/_1

Before connecting
the gas supply, check the rating
plate on the right side of the heater to be sure that the
heater is rated for the same gas to which it will be
connected.
In the United States: The installation must conform with
local codes or, in the absence of local codes, the
National Fuel Gas Code ANSI Z223.1/NFPA
54.
In Canada: The Installation should conform to CGA
B1 49 INSTALLATION
CODES and/or local installation
codes.
Note: The 125 BO comes
with a gas pressure
regulator installed. Disconnecting
or altering the gas
pressure
regulator
will be a violation
of CSA
certification of the unit. The regulator supplied with the
heater is preset for the gas shown on the rating plate to
the correct pressure. It is an appliance level regulator
designed for (low inlet) pressure (less than 1/2 Psig or
14" W.C,).

HIGH

ALTITUDE

INSTALLATION

The pressure regulator
provided
with the heater is
adjusted
to deliver the proper
gas pressure
(as
indicated on the rating plate and in the manual for
altitude up to 2000 feet (660 meters) above sea level.
On appliances
being installed above 2000 ft (660
meters) elevation, the inlet gas pressure should be set
at installation to the value shown below.
Note: The gas pressures
specified
below refer to
pressures taken at the pressure tap on the gas inlet pipe
just above the regulator. See chapter 3.6 for measuring
gas pressure.
MAXIMUM INLET GAS FLOW

PRESSURE

SETTING

0'- 2 000 ft

5.7"

10.5"

2 000 ft- 4 500 ft

4.6"

8.4"

Table 3 Above

4.500 ft consult your local gas provider

GAS LINE SIZING
The gas supply piping should be sized according to the
applicable code for a maximum draw of 11 7,000 BTUH.
Measure the length of gas supply line and use the tables
in Fig. 9 or the gas line manufacturer's
sizing tables to
determine
the
pipe
diameter
necessary
to
accommodate
the BTU demand of the unit. If there are

GAS CONNECTIONS
•

Install a manual gas shut off valve, on the gas supply
line.

•

Install a union when connecting

•

The minimum diameter
connector used is 3/4".

•

National Fuel Gas Code requires that a sediment
trap (drip leg) be installed on gas appliances not so
equipped. The drip leg must be accessible and not
subject to freezing conditions. Install in accordance
with the recommendations
of the serving
gas
supplier.

required

gas supply.
for any appliance

more gas drawing appliances on the line, size the gas
line according
to the total maximum amount of BTU
draw for all appliances.
Note: Under sizing the gas line may result in diminished
output and improper operation. See chapter
procedure to confirm gas pressure.

3.6 for the

When connections are made, check for gas leaks at all
joints. Apply some gas leak detection solution to all gas
fittings. Bubbles are a sign of a leak. A combustible
gas
detector may also be used to detect for leaks.

8716473147

Installation

FOR NATURAL

instructions

GAS

Maximum Capacity of pipe in Cubic Feet of Gas per Hour for Gas Pressure of 0.5 Psig or less and a Pressure drop
of 0.3 in Water Column (0.75mbar).(Based
on a 0.60 Specific Gravity Gas) Btu numbers given in thousands.
Copper tubing is prohibited for use with Natural Gas in the Commonwealth
of Massachusetts
and not recommended
elsewhere.

Follow boxed numbers for piping just one AQ125 BO (example: 3/4" B.I. Natural Gas pipe for 20 ft (6.1m). will I
handle 190,000
btu's (55.7
applicable
chart below.

kWh).

For multiple

appliances

combine

the

total

btu input

load

and

then

refer

Nominal
Iron

Length

Pipe

Internal

Size

Diameter

inches

1/4

0,364

3/8

0.493

of Black

Iron Pipe, Feet

t 00

125

t 50

175

200

0.824278
1.049
0.622

1t32520

t90

t52

130

t05

350
92

285
73

245
63

I 2t5
56

tt5

t95
50

180
46

t70
43

160
40

t50
38

130
34

t201110100110
31
28

55
100
26

1.380

1050

730

590

500

440

400

370

350

320

305

275

25012252101

t t/2

1.6t0

1600

t100

890

760

670

6t0

560

530

490

460

410

380

350

320

2.067

3050

2t00

1650

1450

1270

t150

t050

990

930

870

780

7t0

650

610

Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet
Tube
size,
inches

EHD*

1/2

23
H[_116
30 EHD 3301231

96
188

83
162

75
144

68
131

* EHD

37 EHD

374

325

292

267

value of EH D, the greater

18 EHD

11/4

639456

= Equivalent

Hydraulic

Diameter.

The greater

the gas capacity

the

of the tubing.

FOR LP GAS
Maximum Capacity of Pipe in Thousands of BTU per Hour of Undiluted Petroleum Gases (at 11 inches Water Column Inlet
Pressure) (Based on a Pressure Drop of 0.5 Inch Water Column).
* EHD = Equivalent

Hydraulic

value of EH D, the greater

Nominal

Diameter.

The greater

the gas capacity

the

of the tubing.

Length of FlexbleCorrugatedSta nlessSteel Tubng (CSST), Feet

Iron pipe

Black

size

Length

Tube

Iron Pipe

size
inches

of pipe,

Feet
80

inches
90

100

125

EHD*

150

t,2,2. ,sgt52,2g tt4
to3g65g5375 6g 53
113/4

Ir 567

693

315

2671

237

217

196

185

173

162

146

132

107

732

590

504

448

409

378

346

322

307

275

252

1 1/4

220

149

121

103

913

834

771

724

677

630

567

511

1 1/2

330

229

185

155

141

127

118

108

102

975

866

787

522

433

346

299

264

239

220

204

192

1811

1606

1496

Maximum

Capacity

Petroleum

BTU

Gases

Semi-Rigid

per
(at

Hour

inches

copper
Undiluted
Water

Tubing

Inlet

_18

* Source

on a Pressure
National

- No Additional
number

of fittings

Drop of 0.5 Inch Water

Fuel Gas Code
Allowance

23 EHD
EH_
30 EHD

2541183
91
365

151
74
297

131
64
256

118
58
227

107
5_

521

37 EHD

971

661

528

449

397

359

Copper(LPgas
3utside

Length

ofTubing,

only)

Feet

diameter
nch

Pressure).
(Based

Liquefied

Column

1 1/4

Thousands

100

3/8

1/2

5/8

_107

3/4

329

145

131

1211

112

104

Column)

NFPA 54, ANSI Z223.1

is necessary

for an ordinary

2161181
I

Fig. 8

8 71 6 473 147

Installation

3.6

instructions

Measuring

Connecting

gas pressure

manometer

•

Shut off gas.

•

Remove front cover and locate inlet gas pressure
measuring point on the right side of the gas valve.

•

Loosen screw from test point on the left side of gas
valve and connect manometer tube on test point.

are no loose particles or dirt in the piping. Blow out or
flush the lines before connecting
to the water heater.
Full port valves should be installed on both the cold
water supply and hot water outlet lines to facilitate
servicing the heater (see Fig. 9). For installation on a
private well system with the use of a pressure tank, the
lowest pressure range setting recommended
is 30-50
psi (2.07 and 3.45bar).
Connecting

Static

pressure

test

relief valve (PRV)

A listed pressure relief valve supplied with the heater
must be installed at the time of installation. No valve is

•

Turn gas supply back on.

•

Operate all other gas appliances
system at maximum output.

•

Record static gas pressure
manual.

on same gas piping

reading on back page of

Operating pressure test
•

Run high hot water flow rate.

•

Set flow control knob fully clockwise.

•

Set slide control to the right.

•

Record operating
page of manual.

gas

the pressure

pressure

reading

back

to be placed between the PRV and the
reducing coupling or other restriction may
in the discharge
line. The discharge
line
minimum of 4" above a drain and installed

heater. No
be installed
must be a
such that it

allows complete drainage of both the PRV and the line.
The location of the PRV must be readily accessible for
servicing or replacement, and be mounted as close to
the water heater as possible. See Fig. 9. To install the
PRV, a suitable fitting connected
to an extension on a
"T" fitting can be sweated to the hot water line.
Support all piping.

Gas pressures lower than 5.7" W.C. for Natural Gas or
10.5" W.C. for LP Gas will result in insufficient degree
rise to the hot water being used, and must be corrected.
See Gas Line Sizing under chapter 3.5.

3.7

Water

connections

When facing the heater, the 1/2"cold water inlet is on the
bottom right and the hot water outlet is on the bottom
left.
•

INSTALL
A
UNION
WHEN
CONNECTING
WATER
PIPE
TO
FACILITATE
ANY
NECESSARY
CLEANING AND SERVICING.

Although water piping throughout your structure may be
other than copper, we recommend that copper piping
or suitably rated stainless steel flex line piping be used
for at least three feet before and after the heater (follow

_
Fi9.9

Plumbing
Valve

t
Connections

and

Pressure

Relief

local codes if more stringent).
Never sweat any rigid
piping directly to or beneath the water connections,
damage can occur to the internal water valve from
heating of the pipe. Plastics or other PEX type plumbing
line materials are not recommended
for connecting
directly to the water heater. Keep water inlet and outlet
pipes to no less than 1/2" (12.7ram) diameter to allow the
full flow capacity.
It is recommended
that all water piping below the
heater be properly insulated to avoid heat loss. If
below freezing temperatures are ever anticipated where
the heater is located, insulation material is required and
must be capable of protecting the piping from freezing.
The freeze protection provided with the heater will not
prevent any freeze damage to the exterior water piping.
If the cold and hot connections
to the heater are
reversed,

the heater will not function.

Be certain there

8716473147

Installation

3.8

Electrical

instructions

connections

The 125 BO requires an electrical power supply from a
120VAC 60Hz circuit and must be properly grounded.
A means for switching off the 120VAC power supply
must be provided.

8716473147

Operation instructions

Operation

instructions

4,1

For your safety read before
operating your water heater

8. Observe the pilot flame through the peephole. The
gas valve button should be held down for at least 15
seconds
with pilot burning. When the gas valve
button is released, the pilot should continue to burn.
- If the gas valve button does not pop up when
released,
stop and immediately
call your service
technician or gas supplier.
- If pilot does not stay lit, repeat steps 1 through 8.
- If pilot will not stay lit after several tries, slide the gas
valve button all the way to the left and call service
technician or gas supplier.

A. This appliance employs a piezo-igniter to light the
pilot burner. When lighting the pilot, follow these
instructions exactly,
B. What to do if you smell gas.
•

WHAT TO DO IFYOU SMELL GAS
•

Do not try to light any appliance.

•

Do not touch any electric
phone in your building.

switch;

9. Once pilot remains lit, release the gas valve button.
The heater will now fire at minimum power when
water is drawn at a rate greater than the threshold
flow rate.

do not use any

•

Immediately call your gas supplier from a neighbors
phone. Follow the gas supplier's instructions.

•

If you cannot
department.

reach your gas supplier,

Note: If main burner should fail to ignite, make sure pilot
is burning. If not, repeat lighting steps 1 through 8.
Note: The 125BO
operates
in two modes. See
SETTING THE WATER TEMPERATURE.

call the fire

C. Use only your hand to push in the gas control
buttons. Never use tools. If a button will not push in,
check to make sure the buttons are being pushed in the
proper sequence. Follow these instructions
exactly. If
control
button(s)
are jammed,
close the heater's
individual manual shutoff valve and call a qualified
service technician.
Forced or attempted
repair may
result in a fire or explosion.
D. Do not use this appliance if any part has been under
water. Immediately call a qualified service technician to
inspect the appliance and to replace any part of the
control system and any gas control which has been
under water.

Note:
On
first
time
initial
installation,
existence of air in the
gas supply line and in the water
line may cause
some
ignition
delay. In that case, repeat the
ignition
process until all the air
has been purged.

4.3
•

Slide the gas valve button all the way to the left and
turn off the manual gas valve on the supply line to the
heater.

4.4
4.2

Lighting

instructions

•

1. STOP! Read the previous

•

2. The gas valve must be turned off by sliding the gas
valve button to all the way to the left.

•

3. Wait five (5) minutes to clear out any gas. If you
smell gas, STOP! Follow "B" in the safety information
above on this plate. If you don't smell gas, go to next
step.

•

4. The pilot burner is located behind the peephole
the front center of the cover directly below this
instruction plate.

•

5. Open the sliding viewer window.

•

6. Slide the gas valve button to the right, under
mark (_.

•

7. Fully depress gas valve button and light pilot by
pushing the button marked "_.
This step may have
to be repeated.

safety information.

To turn off appliance

Setting

the water temperature

The 125 BO has a gas control that modulates burner
input in response to flow. Its purpose is to ensure that
the hot water temperature will remain steady, although
the water flow demand
might vary. The output
temperature
can
be
adjusted
with
either
the
temperature adjustment knob or the gas control slide.

the

8716473147

Operation instructions

GAS CONTROL
SLIDE

ADJUSTMENT KNOB

Fig. 10 Temperature Adjustment Controls
Temperature

adjustment knob

The temperature adjustment knob on the front bottom of
the heater (see Fig. 10) adjusts temperature by
adjusting flow capacity. See table 4 for details.

Degree rise
Activation

rate

Max flow rate

90°F

45°F

0.5 GPM

1.1 GPM

2.0 GPM

3.7 GPM

Table 4 Clearances
As the temperature adjustment knob is turned counterclockwise,
the output temperature
will lower and the
activation
rate will be raised. Turning
the knob
clockwise
will raise the temperature
and lower the
activation rate.

Fig. 11

Gas control slide button
The gas control slide button adjusts temperature by
adjusting how much gas is allowed to flow to the
burners.
As the slide is adjusted to the left, the output
temperature will lower, with the lowest setting being the
one flame position 0}. The hottest position is the three
flame position all the way to the right 0_.

8716473147

Maintenance

and service

Maintenance

5,1

Maintenance

and service
intervals

The 125 BO requires periodic
time maintenance
intervals
operating for many years.

5.3

maintenance. The below
should
kept the unit

Every year
_- Inspect

inlet water filter screen (5.2)

_- Inspect

pilot assembly

_- Inspect

burner assembly

and flame
(5.4)

and clean water valve (5.2)

Every 3 to 5 years
_- Rebuild water valve (5.2)
_- Clean pilot assembly
(5.3)

Inspecting

and clean or replace orifice

Water

to fire. If the periodic maintenance is neglected,
costly damage may occur over time.
inlet water

filter

screen

Shut off the installer supplied cold water supply valve.
Disconnect water pipe going to the back of the water
valve. Remove filter from back of water valve. Clean the
filter and inspect for damage. Replace if the filter is at all
damaged. Inspect the top of the water valve for signs of
a water leak or corrosion. If present, rebuild the water
valve. (See below).
Lubricating

the water

valve

A more detailed instruction
at www.boschhotwater.com.

is available on our website
Shut off all water to the

unit and disconnect water pipe going to the back of the
water valve. Disconnect
water pipe going to heat
exchanger
by removing
pin and pulling pipe out.
Loosen two set screws at the base of the gas valve and
drop the water valve down. Separate the two halves by
removing 5 screws on the top of the water valve. Apply
lithium or faucet and valve grease to the pushrod (see
Fig 13, pos. 23). Inspect and clean the venturi (see Fig
13, pos. 29).
Rebuilding

assembly

Main burners

valve

The water valve is the main control that tells the heater

Inspecting

pilot

Disconnect the flame sensor rod cable and the igniter
cable by pulling gently down. Remove two screws holding pilot assembly in place. Loosen compression
fitting
and remove pilot assembly. Note: The orifice sits on top
of the compression fitting DO NOT LOSE. Polish flame
sensor rod and igniter tip with emery cloth. Clean out
pilot assembly and orifice with carburetor
cleaner.
If
heater is an LP unit, replace orifice. Caution:
Do not
enlarge orifice.

5.4
5.2

pilot

The pilot should burn with a clean sharp blue flame. The
flame should fully envelope the bend of the flame sensor
rod. If it does not, clean the pilot assembly per
procedure below.
Cleaning

(5.3)

Every 2 years
_- Lubricate

Pilot

the water

valve

The main burner flames should be blue, with a more
intense blue cone in the center core. Yellow flames
could be a sign of wrong size gas orifices or dirty
burners, or a blockage on the heat exchangers fins. If
some burners have yellow flames while others have
good flames, it is likely that dust, lint or spider webs
have partially clogged the burner venturis. To clean the
burners, contact a gas service person.

5.5

Vent assembly

Inspect the draft hood and heat exchanger fins for signs
of soot build-up or any other foreign material such as
spider webs. Clean out any debris found in the vent
hood. Signs of soot indicate insufficient combustion air
or exhaust draft. Check for vent assembly blockage or
combustion air blockage on the underside of the unit.

5.6

Mineral

scale build-up

The 125 BO, when operated at lower temperatures
settings,
does not accumulate
mineral build-up.
If
however, the heater is used at the higher temperature
settings and the water has a high mineral content,
periodic descaling may be necessary. The heating coils
should be flushed with a descaling
solution. Consult
your dealer or BBT North America for instructions.
Consult your service person.

Several parts within the water valve should be replaced
every 3-5 years. The parts list and instruction can be
found on our website at www.boschhotwater.com.

8716473147

Troubleshooting

6.1

Introduction

millivoltage from the thermocouple
lead to ground.
The expected reading is 24mVDC or greater.

Many of the questions
customers
ask regarding
operation of this unit can be answered by following the
troubleshooting
steps as outlined below. Visit our web
site at www.boschhotwater.com
for more detailed
troubleshooting.
For best results, perform each step
before proceeding to the next. The suggested solutions
may require that the cover be taken off. (See chapter
3.4).

6,2

•

3. Clean or replace the pilot orifice. See chapter
for instructions.

6,3

•

1. Verify the pilot is lit.

•

2. Turn temperature
adjustment
knob all the way
clockwise. Turn hot water faucet to full on position
and fill a quart container. If the container fills in 30
seconds or less your flow rate (1/2 gallon per minute)
is sufficient to activate the heater. If the knob is full
counter clockwise,

was just installed or the gas lines have
on, there may be air in the gas line. To
of the gas line, hold down the gas valve
hitting the piezo ignitor button '_-, every

2. Check to make sure the manual gas shut off valve
is in the open position. Have licensed gas technician
or service person check the presence of gas at the
gas pressure measuring tap on the left side of the
gas control valve. If gas is not present, the regulator
may be locked
up and need
replacing.
See
chapter 3.5 for required gas pressures.

the container

will need to fill in 14

seconds
(1.1 gallons per minute) to activate the
heater. Check for restrictions
in the water line such
as clogged aerators or a clogged
screen if flow rate is not sufficient.

inlet water

filter

•

3. Clean water inlet filter screen. See chapter

•

4. Shut off installer supplied cold water supply valve
(if none installed, install before proceeding). Open all
hot water taps supplied by the 125 BO. Wait 5
minutes and check all taps. Water running is a sign
of a plumbing cross-over. Consult a local plumber or
service person for help in correcting plumbing crossover.

•

5. Verify the cold water supply
right side of the heater.

•

6. Service the water valve.
intervals and instructions.

5.3

Pilot will light but not stay on when
button released

Burners do not ignite with water
flow

•

Pilot will not light

1. If the unit
been worked
bleed air out
button while
second.
•

6.4

is connected

See

chapter

5.2.

to the

5.2

for

1. When lighting pilot ensure the gas valve button is
fully depressed and held down for at least 15 sec
after pilot is lit.

6.5

•

2. Pilot flame should be blue in color and hitting the
thermocouple
tip. See chapter 5.3 for instructions.

•

3. Check the electromagnet
connections.
Electromagnet is located on the right side of the gas valve
behind
the piezo
push-button
assembly.
The
Electromagnet connection is a large aluminum 17mm
hex head nut. The thermocouple
end is a 5 mm brass
nut which screws into the 17 mm nut. Tighten both
nuts snugly but do not over tighten.

1. Shut off installer supplied cold water supply valve
(if none installed, install before proceeding). Open all
hot water taps supplied by the 125 BO. Wait 5
minutes and check all taps. Water running is a sign
of a plumbing cross-over. Consult a local plumber or
service person for help in correcting plumbing crossover.

•

2. Check

•

4. Check

if connections

at the ECO

are loose or

corroded. Clean any corrosion with very fine sand
paper or an eraser and reconnect leads.
•

•

5. If cleaning the terminals attached to the ECO did
not fix the problem, connect a jumper wire between
the two wires attached to the ECO and try to relight
the pilot. If the pilot flame now remains on, the ECO
may be defective and need to be replaced. Do not
leave jumper connected.
6. Have a licensed gas technician verify the proper
operation of the thermocouple
by measuring the

8716473147

Hot water temp fluctuates
to cold

for restrictions

clogged aerators, clogged
inlet water filter screen.

in the water

from hot

line such as

shower head or a clogged

3. If hot water is so hot that a large amount of cold
water must be introduced to lower temperature to
comfortable
level, lower output temperature.
See
chapter 4.4 for instructions.
4. Check the inlet water pressure. For installation on
a private well system with the use of a pressure tank,
the lowest pressure range setting recommended
is
30-50
psi (2.07 - 3.45 bar). Confirm
that the
pressure tank is not water logged.

Troubleshooting

5. Service water valve See chapter
and instructions.

5.2 for intervals

6. ECO (overheat sensor) tripped due to overheating
re-ignite the appliance 10 minutes later. If it happens
again, contact your service person.

6.6

Water

is too

hot

•

1. Check gas type on right side panel rating plate.
NG is a natural gas unit and LP is for liquid propane.

•

2. Since the unit does not measure incoming water
temperature, the output water may be warmer in the
summer than in the winter. Use the slide control to
lower output temperature

as outlined

in chapter

4.4.

•

3. Contact your service person if water temperature
does
not
lower
per
procedure
outlined
in
chapter 4.4.

•

4. Check the inlet water pressure. For installation on
a private well system with the use of a pressure tank,
the lowest pressure range setting recommended
is
30-50
psi (2.07 - 3.45 bar). Confirm
that the
pressure tank is not water logged.

•

5. Service water valve See chapter
and instructions.

•

6. ECO (overheat sensor) tripped due to overheating
period Re-ignite the appliance 10 minutes later. If it
happens again, contact your service person.

6,7

Water

5.2 for intervals

is not hot enough

•

1. Adjust the temperature

per chapter

4.4.

•

2. Shut off installer supplied cold water supply valve
(if none installed, install before proceeding). Open all
hot water taps supplied by the 125 BO. Wait 5
minutes and check all taps. Water running is a sign
of a plumbing cross-over. Consult a local plumber or
service person for help in correcting plumbing crossover.

•

3. While the heater is running with full hot water flow,
the flames should be 3-4" tall off the burner bed. If
the flames are not this tall, have the gas pressure
measured
per chapter3.6
by a license
gas
technician or your service person.

•

4. Service water valve See chapter
and instructions.

5.2 for intervals

8716473147

Interior components and diagram parts list

Interior components

7.1

Interior

and diagram

parts list

components

2
4

7
8
10

Fig.
1
2
3
4
5
6

Functional

scheme

Heat exchanger
Pilot assembly
Burner manifold gas pressure test nipple
Main gas burner
Pilot gas tubing
on/off switch

8716473147

7
8
9

Water valve
Gas control slide
Electronic control box

Temperature adjustment selector

Interior components

7.2

and diagram parts list

Components

diagram

Fig, 13

Components

Diagram

8 716 473 147

Interior components and diagram parts list

7.3

Parts list

Screw

8 716 461 314

Heat exchanger

8 705 406 235 0

Temperature limit

8 707 206 017 0

Hot water pipe

8 716 416 714

Thermocouple

8 707 202 087 0

Burner

8 708 120 298 0 (NG)

Burner

8 708 120 296 0 (LP)

Nozzle (120)

8 708 202 124 0 (NG)

Nozzle (79) (10x)

8 708 202 149 0 (LP)

Washer

8 701 003 010 0

Washer 1" (10x)

8 710 103 060 0

Throttle disc (7,0)

8 700 100 174 0

Pilot burner (41.1)

8 718 105 051 0

Pilot injector (5)

8 708 200 005 0 (NG)

Pilot injector (49)

8 748 200 173 0 (LP)

Sparking plug

8 708 107 002 0

Strainer

8 700 507 055 0

Pipe - Pilot gas

8 700 707 320 0

Gas valve

8 707 021 090 0 (NG)

Gas valve

8 707 021 091 0 (LP)

Magnetic unit

8 707 201 012 0

Piezo igniter

8 708 108 040 0

Nut

8 743 301 025 0

Cable

8 704 401 023 0

Water valve

8 707 002 708 0

Cover

8 705 500 101 0

Sleeve

8 700 306 114 0

Diaphragm (C)

8 700 503 053 0

Wire form spring

8 704 705 024 0

Water strainer

8 700 507 001 0

Selector Screw

8 708 500 289 0

Volumetric water governor

8 705 705 027 0

Venturi (23s)

8 708 205 279 0

Gas regulator

8 716 487 043 (LP)

Gas regulator

8 716 487 044 (NG)

Anti frost device

8 716 459 336

Thermostat

8 716 459 273

Screw

8 703 401 051 0

Cold water pipe

8 716 416 715

34
Table 5

8 716 473 147

Protecting the environment

Protecting

the environment

Packing
The packing

box may be fully recycled

the recycling

symbol

as confirmed

&_3'

Components
Many parts in the heater can be fully recycled in the end
of the product life, Contact your city authorities
for
information about the disposal of recyclable products.

Saving water resources:
_- Make sure you close all the taps after any use. Avoid
leaving the taps dripping. Repair any leaking tap.
_- Define the temperature you want, This way you have
the precise water flow needed (mixing cold water to
regulate temperature will increase the water flow with
consequent waste of water).

For increased safety shut off the appliance from
the main water supply if your are staying away
from home for a considerable time.
At below freezing temperatures, disconnect the
plumbing connections to the heater and allow
the heater to drain.
To prevent any freeze damage, introduce short
bursts of compressed air (20-40 psi) through
these connections to remove the residual water
in the horizontal pipes and water valve.

8 716 473 147

Twelve Year Limited Warranty

Twelve

Year

Limited

Warranty

General
Aquastar
water
heaters
are warranted
by the
Manufacturer
(BOSCH)
through BBT North America.
BBT North America (BBTNA) will furnish a replacement
heat exchanger and will furnish a replacement of any
other part which fails in normal use and service within
the applicable periods specified below, in accordance
with
the terms
of this
warranty.
The
BBTNA
replacement will be warranted for the unexpired portion
of the original warranty. This warranty will be valid only
for water heaters in possession of the original purchaser
as recorded on the warranty card.

costs associated with service, removal or re-installation
of the original water heater or a replaced water heater.
Note:

the water

heater

must be free of

damaging scale deposits and not subject
to gas pressures
greater
than those
shown on the rating plate, which must not
be altered, defaced or removed.

How to Make a Claim
Any claim for warranty parts should be made to your
local dealer, distributor or to BBTNA. If BBTNA, please
contact the Technical Support Department:

The Heat Exchanger
If the heat exchanger fails within twelve (12) years after
the original installation and operation BBTNA will
furnish a replacement heat exchanger. However, if the
water heater is installed in other than a single family
dwelling this heat exchanger warranty is limited to two
(2) years from date of original installation and operation.

BBT NORTH AMERICA
Bosch Group
340 Mad River Park
Waitsfield, VT 05673
Phone: 800-642-3111
www.boschhotwater.com

Exceptions
This warranty will not apply:
•

1. to defects or malfunctions
resulting from failure to
properly install, operate
or maintain
the unit in
accordance with the printed instructions provided;

•

2. to damage or abuse, accident,
and other acts of nature;

•

3. to damage resulting from operation with either the
flame sensor rod or overheat sensor removed;

•

4. to failure of the heat exchanger resulting from the
operation
of the water
heater
in a corrosive
atmosphere or at water temperatures exceeding the
maximum rating, or if the water heater is not supplied
with potable water;

•

5. to defects or damage cause by any attachment
or modification,
including any energy-saving device.

neglect

or freezing

All Other Parts
If any other part fails within two (2) years after original
installation and operation, BBTNA will furnish a
replacement part free of charge.
Shipping costs

In most cases, the dealer or distributor will be able to
promptly honor your claim and subsequently notify
BBTNA. However, all replacements are made subject to
validation by BBTNA of in-warranty coverage. The
damaged or defective item must be made available in
exchange for the replacement.
Miscellaneous
No one is authorized to make any other warranties on
behalf of BBTNA. It is expressly understood that the
replacement warranty of BBTNA shall be in lieu of any
and all other warranties, express or implied, including
warranties of merchantability
or fitness for a particular
use or purpose, and further that BBTNA shall not be
liable for any loss or damage directly or indirectly arising
from the use of the hot water heater, or for any
consequential
damages
arising
from
such
use
(including damages from water leakage). BBTNA sole
liability with respect to any defect shall be for the
replacement of the defective part(s). Some states do
not allow such limitations and exclusions, so the above
may not apply to you.
This warranty gives specific legal rights. You may also
have other rights which vary from state to state.

In addition to supplying the replacement part(s),
BBTNA will provide ground service delivery for these
parts. Expedited or upgraded shipping will be charged
to the customer.
Service

Labor Costs

This warranty
does
not cover
any labor
costs
associated
with service, removal or re-installation
of
part(s). All such costs must be borne by the Purchaser.
Additionally,
this warranty does not cover any labor

8 716 473 147

Installer Checklist,

to be performed

by installer upon installation

Serial Number
(8 digit serial number

Gas Pressure Reading*
Building

Water

Average

Winter Temperature

Average

Summer Temperature

Installing

is located

on rating plate on right side panel)

Static

Pressure

Operating
Range if on Well system

Company

Installer name
Address
Phone
* See Chapter
Installation

3.6 and gas pressure

table (to be filled out by installer)

manual should be left with the owner after the installation

Replacement

Parts available

is tested

and completed

from:

BBT NORTH AMERICA
Bosch Group
Bosch Water Heating
340 Mad River Park
Waitsfield,
VT 05673
Phone 800-642-3111
Fax (802)

VULCANO

Termodomesticos

S.A,

Estrada de Cacia
3801

- 856 Aveiro - PORTUGAL

496-6924

www.boschhotwater.com
techsupport@

Recycled

paper

boschhotwater.com

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BOSCH Water Heater, Gas Manual L0803440

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