Trane Rtaa 70 125 Ton Users Manual RTAA_SB

RTWA 70-125 TON to the manual da09da43-29ef-49f5-8bb8-6a308b5c8a56

2015-01-21

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Diagnostic
Troubleshooting
Repair
Series R®
70-125 Ton Air-Cooled and Water-Cooled
Rotary Liquid Chillers

Model
RTAA 70-125 Ton
RTWA 70-125 Ton
RTUA 70-125 Ton

August 2005
© American Standard Inc. 2005

RLC-SVD03A-EN

NOTICE: Warnings and Cautions appear at appropriate sections throughout this literature. Read these carefully.

WARNING:

Indicates a potentially hazardous situation which, if not
avoided, could result in death or serious injury.

CAUTION: Indicates a potentially hazardous situation which, if not
avoided, may result in minor or moderate injury. It may also be used to
alert against unsafe practices.
CAUTION: Indicates a situation that may result in equipment or propertydamage only accidents.

Important - Read This First!
This manual is intended for experienced service personnel familiar with the
proper use of electrical diagnostic instruments and all personal safety
procedures when working on live electrical circuits.
This Manual is not intended for individuals who have not been properly trained
in handling live electrical circuits.

Environmental Concerns!
Scientific research has shown that certain man-made chemicals can affect the
earth’s naturally occurring stratospheric ozone layer when released to the
atmosphere. In particular, several of the identified chemicals that may affect the
ozone layer are refrigerants that contain Chlorine, Fluorine and Carbon (CFCs)
and those containing Hydrogen, Chlorine, Fluorine and Carbon (HCFCs). Not all
refrigerants containing these compounds have the same potential impact to the
environment. Trane advocates the responsible handling of all refrigerants—
including industry replacements for CFCs such as and HCFCs and HFCs.

Responsible Refrigerant Practices!
Trane believes that responsible refrigerant practices are important to the
environment, our customers, and the air conditioning industry. All technicians
who handle refrigerants must be certified. The Federal Clean Air Act (Section
608) sets forth the requirements for handling, reclaiming, recovering and
recycling of certain refrigerants and the equipment that is used in these service
procedures. In addition, some states or municipalities may have additional
requirements that must also be adhered to for responsible management of
refrigerants. Know the applicable laws and follow them.

WARNING
Contains Refrigerant!
System contains oil and refrigerant under high pressure. Recover refrigerant to
relieve pressure before opening the system. See unit nameplate for refrigerant
type. Do not use non-approved refrigerants, refrigerant substitutes, or refrigerant
additives.
Failure to follow proper procedures or the use of non-approved refrigerants,
refrigerant substitutes, or refrigerant additives could result in death or serious
injury or equipment damage.

RLC-SVD03A-EN

Contents
General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Service Philosophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
System Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
System Level Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Interprocessor Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
IPC Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Troubleshooting Modules Using IPC Diagnostics . . . . . . . . . . . . . . . . . . . . . . . 9
Troubleshooting Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Temperature Sensor Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Temperature Sensor Checkout Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Compressor Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Restart Inhibit Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Compressor Start/Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Variable Speed Inverter/Condenser Fan Control . . . . . . . . . . . . . . . . . . 21
Outdoor Air Temperature and Fan Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
VSF Inverter Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Current Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
CT and MCSP Compressor Current Input Checkout Procedure . . . . . . . . . . . 24
Under-Over Voltage Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Under-Over Voltage Transformer Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Compressor Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Checkout Procedure for MCSP Load/Unload Outputs . . . . . . . . . . . . . . . . . . 35
Checkout Procedure for the Slide Valve and Load/
Unload Solenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Checkout Procedure for MCSP Step Load Output . . . . . . . . . . . . . . . . . . . . . 39
Checkout Procedure for Step Load Solenoid Valve
and Piston . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Module Power and Miscellaneous I/O . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Clear Language Display (CLD) 1U6 Keypad Overview . . . . . . . . . . . . . . . . . . 42
Chiller Module (CPM) (1U1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Options Module (CSR) (1U2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Electronic Expansion Valve Module (EXV) (1U3) . . . . . . . . . . . . . . . . . . . . . . . 58
Compressor Module (MCSP) (1U4 AND 1U5) . . . . . . . . . . . . . . . . . . . . . . . . . 72
Interprocessor Communication Bridge Module (IPCB) (1U7) . . . . . . . . . . . . . 78
LonTalk® Communications Interface - Chillers Module
(LCI-C) (1U8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Variable Speed Fan System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Inverter Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Troubleshooting Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Other Service Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Service Pumpdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Circuit Lockout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Circuit Diagnostic Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

RLC-SVD03A-EN

General Information
The Unit Control Modules (UCMs) described in this troubleshooting guide
provide a microprocessor based refrigeration control system, intended for
use with Trane 70-125 ton helical rotor chillers. Six types of modules are
used, and throughout this publication will be referred to by their abbreviations
or their Line Wiring Drawing Designations, see Table 1.
Table 1

Unit Control Module Designations

Line Drawing
Designation

Controller Name
Chiller Module

Abbrev.
CPM

1U2

Options Module

CSR

1U3

Expansion Valve Module

EXV

1U4 & 1U5

Compressor Module

MCSP A & B

1U6

Clear Language Display

CLD

1U7

Interprocessor
Communications Bridge
(Remote Display Buffer)

IPCB

Service Philosophy
With the exception of the fuses, no other parts on or within the modules are
serviceable. The intent of the troubleshooting is to determine which module
is potentially at fault and then to confirm a module problem. This is done
either through voltage or resistance measurements at the suspected input or
output terminals or by checking related wiring and external control devices
(connectors, sensors, transformers, contactors etc.) in a process of elimination. Once a problem has been traced to a module, the module can be
easily replaced using only basic tools. In general, all dip switch settings of the
replaced modules should be copied onto the replacement module's dip
switches before applying control power. CPM replacement is more involved
as there are numerous configuration and set-up items that must be
programmed at the Clear Language Display in order to insure proper unit
operation.
It is helpful to include with the return of a module, a brief explanation of the
problem, sales office, job name, and a contact person for possible follow-up.
The note can be slipped into the module enclosure. Early and timely
processing of Field Returns allows for real measurements of our product
quality and reliability, providing valuable information for product improvement
and possible design changes.

RLC-SVD03A-EN

General Information
System Description
The CPM is the master module and coordinates operation of the entire
system. One is used per chiller. The MCSP is a compressor protection
module with one being used for each of the compressors in the chiller. The
EXV is the expansion valve controller module which controls two Electronic
Expansion Valves. There is one valve on each of the two refrigeration circuits.
The CLD is a two line, 40 character alphanumeric interface to the system. It
allows the operator to read operating and diagnostic information, as well as
change control parameters. The Interprocessor Communications Bridge
(IPCB) provides an extension of the IPC link to the Remote Clear Language
Display, while protecting the integrity of the IPC communications link
between the local modules.
The CSR is an optional communications module which allows for communications between the chiller and a remote building automation system (i.e.
Tracer, Tracer Summit, Generic BAS).
All modules in the system communicate with each other over a serial interprocessor communications bus (IPC) consisting of a twisted wire pair “daisy
chain” link and RS485 type signal levels and drive capability. Multiple modules
of the same type (i.e. MCSPs) in an operating system are differentiated by
address dip switches.
All the modules operate from 115VAC, 50 or 60Hz power and each have their
own internal step-down transformer and power supply. Each is individually
fused with a replaceable fuse. The modules also are designed to segregate
their high and low voltage terminals by placing the high voltage on the right
side of the module and the low voltage on the left. When stacked, segregation is maintained.
In addition to the modules, there are a number of “system level” components that are closely associated with the modules. These components were
specifically designed and/or characterized for operation with the modules. For
this reason, the exact Trane part must be used in replacement.

System Level Components
Description
The following is a list of all the components that may be found connected to
the various modules.
Transformer, Under/Over voltage
Current Transformer - Compressor
Evap EntlLvg Water Temp Sensor Pair
Sat Evap/Cprsr Suc Rfgt Temp. Sensor Pair
Sat Cond RfgtIOil Temp Sensor Pair
Outdoor Air Temperature Sensor
Zone Temp Sensor
Connector (UCM mating connectors)
Connector Keying Plug
Electronic Expansion Valve
RLC-SVD03A-EN

General Information
High Pressure Cutout Switch
Low Pressure Cutout Switch
Variable Speed Fan Drive
Motor Temperature Thermostats
Slide Valve Load/Unload Solenoids
Step Load Solenoid Valve
Chiller Module (CPM) IU1
The CPM module performs machine (chiller) level control and protection
functions. Only one CPM is present in the chiller control system. The CPM
acts as the master controller to the other modules, running top level machine
control algorithms, initiating and controlling all inter-module communication
over the IPC, and providing parameters and operational requests (i.e. loading
and unloading, starting and stopping) to the other modules in the system via
the IPC. The CPM also contains nonvolatile memory, which allows it to
remember configuration and set-up values, setpoints, historical diagnostics
etc. for an indefinite period of time following a power loss. Direct hard wired
I/O associated with the CPM includes low voltage analog inputs, low voltage
binary inputs, 115 VAC binary inputs and 115 VAC (rated) relay outputs. See
Chiller Module (CPM) (1U1) on page 46 for further details.
Compressor Module (MCSP) 1U4 and 1U5
The MCSP module employs the input and output circuits associated with a
particular compressor and refrigeration circuit. Two MCSP modules are used
in the UCM system, one for each compressor. Included are low voltage
analog and digital circuits, 115 VAC input, and 115 VAC output switching
devices. The output switching devices associated with the compressor motor
controlling function are contained in this module. The outputs of this module
control one compressor motor stop/start contactor, one compressor motor
transition contactor, one oil heater, three solenoid valves (compressor load,
compressor unload, step loader), and up to four fan motor contactors or
groups of contactors. Refer to the chiller's line wiring diagrams for details. Dip
switches are provided for redundant programming of the compressor current
overload gains, and for unique IPC address identification during operation.
Inputs to this module include motor temperature thermostats, thermisters,
and safety switches. See Compressor Module (MCSP) (1U4 AND 1U5) on
page 72 for details.
Expansion Valve Module (EXV) 1U3
The EXV module provides power and control to the stepper motor driving the
electronic expansion valves of the chiller. Each module handles two valves,
one in each refrigeration circuit.
Input to the EXV Module is provided by four temperature sensors (two per
refrigeration circuit). The sensors are located in the respective refrigeration
circuits of the chiller and sense Saturated Evaporator and Suction temperatures and calculate the superheat temperatures. High level operational
commands as well as superheat setpoints are received by the EXV Module
over the IPC from the CPM module to modulate the EXV's.

RLC-SVD03A-EN

General Information
Real time data for temperatures, diagnostics and control algorithms etc. are
made available to the CPM and the other modules for display and for input to
higher level functions. See Electronic Expansion Valve Module (EXV) (1U3) on
page 58 for details.
Options Module (CSR) 1U2
The CSR module is an optional part of the system and employs communications circuits for interface to Trane Building Automation Systems, done
through 1C17. The CSR also provides inputs for hard wired external setpoints
and reset functions. Included are low voltage analog and digital input circuits.
See Options Module (CSR) (1U2) on page 50 for details.
Clear Language Display (CLD) 1U6
The CLD Module provides an operator interface to the system, through a two
line, 40 character alphanumeric display. Three reports may be displayed and
various operating parameters may be adjusted by depressing a minimal
number of keys on the CLD. Also, chiller Start/Stop functions may be
performed at this keypad. See Clear Language Display (CLD) 1U6 Keypad
Overview on page 42 for details.
Interprocessor Communication Bridge (IPCB) 1U7
The IPCB module allows connection of a Remote Clear Language Display
module to the UCM, for distances of up to 1500 feet. The Remote Clear
Language Display communicates with the UCM, utilizing the same IPC
protocol, and provides most of the same functions as the local CLD. The IPCB
then serves to protect the UCM's IPC if wires to the Remote CLD become
shorted or broken. See Section 2 and on page 75 for details.

RLC-SVD03A-EN

Interprocessor Communications
The respective modules communicate with each other via an InterProcessor
Communication link (IPC). The IPC allows the modules to work in a coordinated manner with the CPM directing overall chiller operation while each
module handles specific subfunctions. This IPC link is integral and necessary
to the operation of the Unit Controls and should not be confused with the
Optional ICS (Integrated Comfort System) communication.
In the IPC communication protocol scheme, the CPM acts as the initiator and
the arbitrator of all module communication. The CPM essentially requests all
the possible “packets” of information from each module in turn, (including
itself), in a predefined serial sequence. The other modules act as
“responders” only and cannot initiate communication. Modules which are not
currently responding to a specific request, can listen to the data and thus,
indirectly, they communicate with each other. It is helpful to remember when
troubleshooting that a module must be able to hear a request for its information from the CPM, or it will not talk.
The link is non-isolated, which means that a good common ground between
all the modules is necessary for trouble-free operation (provided by the
module enclosures' mounting using star washers). Also, the link requires
consistent polarity on all of the module interconnections. Connections
between modules are made at the factory, using unshielded #18 gauge
twisted pair cable terminated into a 4-position MTA type connector (orange
color code). This connector is plugged onto the 4 pin IPC connection jack
designated as J1, located in the upper left corner of the PC board edge on all
of the modules. The 4 pins actually represent 2 pairs of communications
terminals (J1-1 (+) internally connected to J1-3, and J1-2 (-) internally
connected to J1-4) to allow for easy daisy chaining of the bus.

IPC Diagnostics
The modules, in order to work together to control the chiller, must constantly
receive information from each other over the IPC. Failure of certain modules
to communicate or degradation of the communication link, could potentially
result in chiller misoperation. To prevent this situation, each module monitors
how often it is receiving information from designated other modules. If a
module fails to receive certain other module's transmitted data over a 15
second time period it will:
1.

On its own, take specific action to safely shut-down (or to default) its controlled loads.

2. Report a diagnostic to the CPM (over the IPC link).
The CPM (if it properly receives such) will then report and display the
diagnostic on the Clear Language Display accordingly. The diagnostic will:
•

identify which module is reporting the communication problem and

•

identify which module was to have sent the missing information.

The CPM itself will then send out further commands to the other modules to
shutdown or take default actions as the particular case may warrant.
All IPC diagnostics are displayed in the Clear Language Display's diagnostics
section. For example, “Chiller Mod indicating Options Mod Comm Failure”
indicates that the CPM Module has detected a loss of IPC communication
8

RLC-SVD03A-EN

Interprocessor Communication
from the Options Module. When some problem exists with the IPC link or a
module fails, it is not uncommon for more than one of these IPC diagnostics
to be displayed. Note that only those diagnostics that are indicated to be
active currently exist. All other historic diagnostics should be disregarded for
the purpose of the following troubleshooting discussion. See RTAA-IOM-4 for
a complete listing of diagnostics.

Troubleshooting Modules Using IPC Diagnostics

Improperly set IPC address dip switches

2. Opens or shorts in the twisted pair IPC wiring or connectors
3. Loss of power to a module
4. Internal module failure
5. Improper connections on terminal J2
6. High levels of EMI (Electro-Magnetic Interference)
7.

Module specific function selected without the Options Module.

These are discussed in more detail in the following paragraphs.
1.

Improperly set IPC address dip switches:
This could result in more than one module trying to talk at the same time,
or cause the mis-addressed module to not talk at all. Only the MCSP and
the EXV modules have IPC address dip switches, found in the upper left
hand portion of the Module labeled as SW-1. The proper dip switch setups are shown in Table 2.

2. Opens or shorts in the twisted pair IPC wiring or connectors:
One or more modules may be affected by an open or a short in the IPC
wiring, depending on the location of the fault in the daisy chain. The diagram below shows the daisy chain order and is helpful in diagnosis of an
open link.
Extreme care should be used in making any dip switch changes or when
replacing MCSP modules. “Swapping” of addresses on the MCSPs
cannot be detected by the communication diagnostics discussed above
and serious chiller misoperation will result.

RLC-SVD03A-EN

Interprocessor Communication
*
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5

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5

*
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5
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5AND5AREMUTUALLYEXCLUSIVEOPTIONS
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Figure 1

IPC Link Order For 70-125 Ton RTAA

RLC-SVD03A-EN

Interprocessor Communication
.

Table 2

IPC Address Dip Switch (SW1) Settings for MCSP an EXV Modules

MODULE

DESIG.

CONTROLLING

MCSP “A”

1U4

COMPRESSOR A

DIP SWITCH SETTING
SW1-1
SW1-2
OFF
OFF

MCSP “B”

1U5

COMPRESSOR B

OFF

EXV

1U3

CKTS. 1 & 2

OFF

3. Loss of power to a module:
Generally a power loss to a particular module will only affect communications with that module. The module can usually be identified by analysis
of the IPC diagnostics. (When the display is blank, check power at the
CLD). Loss of power can most directly be diagnosed by measuring the
AC voltage at the top of the fuse with respect to the neutral of the power
connection (pins 4 or 5) on the terminal just below the fuse:

833(55,*+7
&251(52)
02'8/(

IXVHGVLGH

)86(
XQVZLWFKHGVLGH
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Figure 2

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1

Module Fuse and Power Connection, Except CLD

4. Internal module failure:
Internal module failures usually result only in communication loss to the
failed module, but could, in some cases, affect all the modules because
the failed module may “lock up” the IPC bus and prevent all communications. The former can be identified by analyzing all of the active IPC diagnostics. The latter can be identified in a process of elimination, whereby
each module, in turn, is taken out of the IPC link and a jumper installed in
its place. See Figure 3. The CPM can then be reset and the new IPC diagnostics that result can be analyzed.

RLC-SVD03A-EN

Interprocessor Communication
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Figure 3
IPC Jumper For Bypassing Modules (to be inserted into MTA
connector in place of module)

5. Improper connections to terminal J2:
Jack J2, present on all modules except CLD, should have no connections.
This input is for manufacturing test purposes only and any connections,
shorts, etc. will potentially cause the module to not respond, respond to
the wrong address, or (in the case of the CPM) fail to initiate any communications and thus fail the entire IPC.
6. High levels of Electro-Magnetic Interference:
The modules and the IPC have been qualified under severe EMI (both
radiated and conducted) and the system was determined to be immune
to all but extremely high noise levels. Always be sure to close and latch
the control panel cabinet doors as the panel enclosure provides significant shielding and is integral in the overall noise immunity of the control
system.
7.

Module specific function selected without the Options Module:
If any of the functions on the Options Module are selected but the
Options Module is not present, the UCM will look for this module and
generate an error. The Options Module functions include Chilled Water
Reset, Ice Machine Control, External Chilled Water Setpoint, External
Current Limit Setpoint, and Tracer/Summit Communications.

Troubleshooting Procedure
1.

Place the CPM in “Stop”. Record the active IPC diagnostics as shown in
the Diagnostics Report of the CLD. The communication failure diagnostics and their meanings are shown in IPC Diagnostics of the RTAA-IOM-4
manual.

2. Determine which modules are not talking. These modules must be
affected by one of the previously stated problems. If there is a group of
modules not talking, suspect a wiring problem early in the daisy chain
link. If only one module is not talking, suspect a loss of power or blown
fuse.

RLC-SVD03A-EN

Interprocessor Communication
3. Determine which modules are still talking. Wiring up to these is likely to
be OK.
4. Try disconnecting the link or jumping out modules in the link at various
places (use Figure 1). Reset the diagnostics and note which diagnostics
reappear.
Here are some examples of IPC diagnostics:
Diagnostics present:
Chiller Mod Indicating EXV Mod Communications
Cprsr A Indicating EXV Mod Communications
Cprsr B Indicating EXV Mod Communications
The CPM and both MCSP modules are detecting a loss of communications
with the EXV. Suspect power to the EXV or its fuse or a wiring problem
downstream of the MCSP A and B modules.
Diagnostics present:
Chiller Mod Indicating Options Mod Communications
Chiller Mod Indicating EXV Mod Communications
Chiller Mod Indicating Cprsr A Communications
Chiller Mod Indicating Cprsr B Communications
The CPM is reporting that it cannot talk to any of the other modules. Suspect
a shorted IPC bus or a module locking up the bus. The CPM could also be bad
and not be sending recognizable tokens. Discriminating between these possibilities is done by disconnecting the link or jumping out modules in the link at
various places. Refer to Item 4 in Troubleshooting Modules (Troubleshooting
Modules Using IPC Diagnostics on page 9) for the procedure and the IPC
Jumper for bypassing the Modules.
Diagnostics present:
Chiller Mod Indicating Cprsr B Communications
EXV Mod Indicating Cprsr B Communications
The CPM and EXV have both detected a communication loss with MCSP B.
Suspect the address switch on MCSP B or a power/fuse problem.
Diagnostics present:
Chiller Mod Indicating Cprsr A Communications
Chiller Mod Indicating Cprsr B Communications
EXV Mod Indicating Cprsr A Communications
EXV Mod Indicating Cprsr B Communications
The CPM and EXV have both detected a communication loss with MCSP A
and MCSP B. Suspect that the address switches on both modules are set to
the same address. Wiring is probably OK since the EXV can talk to the CPM.
Diagnostics present:
Chiller Mod Indicating Cprsr B Communications
Chiller Mod Indicating Cprsr A Communications
Chiller Mod Indicating EXV Mod Communications

RLC-SVD03A-EN

Interprocessor Communication
The CPM has detected loss of communications with MCSP A, MCSP B,
and EXV. Suspect an open early in the IPC link between the CPM and
MCSP B.
There are a large number of possible combinations of diagnostics. One must
deduce what is causing the problem using all available information.
If the CLD Comm link to the CPM is broken, the message is:
No Communication, Data Not Valid

RLC-SVD03A-EN

Temperature Sensor Checkout
With the exception of the thermostats located in the motor windings of the
screw compressors, all the temperature sensors used on the UCMs are
negative temperature coefficient (NTC) thermistors. The thermistors
employed all have a base resistance of 10 Kohms at 77F (25C) and display a
decreasing resistance with an increasing temperature. The UCMs “read” the
temperature by measuring the voltage developed across the thermistors in a
voltage divider arrangement with a fixed internal resistance. The value of this
“pull-up” resistor is different depending on the temperature range where the
most accuracy is desired. The voltage source for this measurement is a
closely regulated 5.0 VDC supply.
An open or shorted sensor will cause the UCM to indicate the appropriate
diagnostic. In most cases, an open or short will cause a CMR or MMR
diagnostic that will result in a machine or circuit shutdown. Open or shorts on
less critical Outdoor Air or Zone Temperature sensors will result in an
Informational Warning Diagnostics and the use of default values for
that parameter.

Temperature Sensor Checkout Procedure

Measure the temperature at the sensor using an accurate thermometer.
Record the temperature reading observed.

2. With the sensor leads connected to the UCM and the UCM powered,
measure the DC voltage across the sensor leads at the terminal or probe
the back of the MTA plug.
NOTE: Always use a digital volt-ohmmeter with 10 megohm or greater input
impedance to avoid “loading down” the voltage divider. Failure to do so will
result in erroneously high temperature calculations.
3. Locate the appropriate sensor table. Table 3: Evaporator Water and
Refrigerant Temperature Sensors, Table 4: Saturated Condenser Refrigerant and Entering Oil Temperature Sensors. Then compare the temperature in the table corresponding to the voltage reading recorded in Step 2
with the actual temperature observed in Step 1. If the actual temperature
measured falls within the allowable tolerance range, both the sensor and
the UCM's temperature input circuits are operating properly. However, if
the actual temperature is outside the allowable sensor tolerance range,
proceed to Step 4.

RLC-SVD03A-EN

Temperature Sensor Checkout
4. Again measure the temperature at the sensor with an accurate thermometer; record the temperature reading observed.
5. Remove the sensor leads from the terminal strip or unplug the respective
MTA. Measure the resistance of the sensor directly or probe the MTA
with a digital volt-ohmmeter. Record the resistance observed.
6. Next, with the sensor still disconnected from the module, check the
resistance from each of the sensor leads to the control panel chassis.
Both readings should be more than 1 Megohm. If not, the sensor or the
wiring to the sensor is either shorted or leaking to chassis ground and
must be repaired.
7.

Select the appropriate sensor table and locate the resistance value
recorded in Step 5. Verify that the temperature corresponding to this
resistance value matches (i.e. within the tolerance range specified for
that sensor) the temperature measured in Step 4.

8. If the sensor temperature is out of range, the problem is either with the
sensor, wiring, or the MTA connector (if applicable). If an MTA connector
is used and the thermistor reads open, first try cutting off the MTA, stripping a small amount of insulation from the sensor wire's end and repeating the measurement directly to the leads. Once the fault has been
isolated in this manner, install a new sensor, connector or both. When
replacing a sensor, it is easiest to cut the sensor wire near the MTA end
and splice on a new sensor using wire nuts.
9. A decade box can be substituted for the sensor and any sensor table
value used to relate resistance to temperature. By removing the MTA
plug and applying the resistance to the proper pin terminals, the temperature, as sensed by the UCM, can be confirmed. Using the CLD menu displays, scroll to the display of the temperature of interest.
NOTE: All displayed temperatures are slew rate limited and only accurate
within a specified normal range. It is therefore important to be certain that
the temperature readings are stable and that adequate time, up to 1 minute,
is allowed after step changes in resistance inputs are made.
10. In all instances where module replacement is indicated, first perform the
power supply/fuse check according to the information in the section
“Module Power and Miscellaneous I/O” starting on page 41.

RLC-SVD03A-EN

Temperature Sensor Checkout
.

Table 3
Sensor Conversion Data: Outdoor Air (6RT3), Entering and Leaving Evap Water Temp Matched
Pairs (6RT7, 6RT8), and Saturated Evap and Comp Suction Refrigeration Temp (6RT9, 3B1RT5; 6RT10, 4B1RT6)
Actual
Temp.
(F)

Actual
Resistance
(Ohms)

Thermistor
Voltage
(Volts DC)

Actual
Temp.
(F)

Actual
Resistance
(Ohms)

Thermistor
Voltage
(Volts DC)

Actual
Temp.
(F)

Actual
Resistance
(Ohms)

Thermistor
Voltage
(Volts DC)

-20.0
-19.0
-18.0
-17.0
-16.0
-15.0
-14.0
-13.0
-12.0
-11.0
-10.0
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
16.0
17.0
18.0
19.0
20.0
21.0
22.0
23.0
24.0
25.0
26.0
27.0
28.0
29.0

170040.3
164313.4
158796.5
153482.9
148365.0
143432.2
138679.6
134098.6
129684.9
125428.5
121326.1
117369.6
113554.9
109876.5
106328.1
102904.9
99602.3
96416.1
93341.6
90374.2
87510.3
84745.9
82077.1
79500.5
77012.3
74609.7
72288.8
70047.4
67881.9
65790.2
63768.7
61815.3
59927.8
58103.1
56339.6
54634.7
52986.4
51392.6
49851.6
48360.9
46919.2
45524.6
44175.6
42870.3
41607.6
40385.3
39202.7
38057.9
36950.0
35877.4

4.448
4.434
4.414
4.395
4.380
4.360
4.341
4.321
4.302
4.282
4.263
4.238
4.219
4.194
4.175
4.150
4.126
4.106
4.082
4.058
4.033
4.004
3.979
3.955
3.926
3.901
3.872
3.848
3.818
3.789
3.760
3.730
3.701
3.672
3.643
3.608
3.579
3.550
3.516
3.486
3.452
3.418
3.389
3.354
3.320
3.286
3.257
3.223
3.188
3.154

30.0
31.0
32.0
33.0
34.0
35.0
36.0
37.0
38.0
39.0
40.0
41.0
42.0
43.0
44.0
45.0
46.0
47.0
48.0
49.0
50.0
51.0
52.0
53.0
54.0
55.0
56.0
57.0
58.0
59.0
60.0
61.0
62.0
63.0
64.0
65.0
66.0
67.0
68.0
69.0
70.0
71.0
72.0
73.0
74.0
75.0
76.0
77.0
78.0
79.0

34838.9
33833.3
32861.4
31935.3
31038.7
30170.5
29329.5
28515.0
27725.9
26961.4
26220.8
25503.0
24807.5
24133.3
23479.7
22846.1
22231.9
21636.2
21058.7
20498.4
19955.0
19427.9
18916.5
18420.3
17938.8
17471.6
17018.0
16577.8
16150.5
15735.7
15332.9
14941.7
14561.9
14193.0
13834.6
13486.5
13148.3
12819.8
12500.5
12190.2
11888.7
11595.6
11310.7
11033.7
10764.4
10502.6
10248.0
10000.4
9759.6
9525.4

3.120
3.086
3.047
3.018
2.983
2.949
2.910
2.876
2.842
2.808
2.773
2.739
2.705
2.671
2.637
2.603
2.568
2.534
2.505
2.471
2.437
2.402
2.368
2.334
2.305
2.271
2.236
2.207
2.173
2.144
2.109
2.080
2.046
2.017
1.987
1.958
1.924
1.895
1.865
1.836
1.807
1.777
1.753
1.724
1.694
1.670
1.641
1.616
1.587
1.563

80.0
81.0
82.0
83.0
84.0
85.0
86.0
87.0
88.0
89.0
90.0
91.0
92.0
93.0
94.0
95.0
96.0
97.0
98.0
99.0
100.0
101.0
102.0
103.0
104.0
105.0
106.0
107.0
108.0
109.0
110.0
111.0
112.0
113.0
114.0
115.0
116.0
117.0
118.0
119.0
120.0
121.0
122.0
123.0
124.0
125.0
126.0
127.0
128.0
129.0
130.0

9297.5
9075.9
8860.2
8650.4
8446.2
8247.5
8054.1
7865.8
7682.5
7504.2
7330.5
7161.4
6996.7
6836.3
6680.1
6528.0
6379.8
6235.5
6094.8
5957.8
5824.3
5694.2
5567.4
5443.8
5323.3
5205.9
5091.5
4979.9
4871.1
4765.0
4661.5
4560.6
4462.2
4366.3
4272.6
4181.3
4092.2
4005.3
3920.5
3837.7
3756.9
3678.1
3601.1
3526.5
3453.6
3382.4
3313.0
3245.1
3178.9
3114.2
3051.0

1.533
1.509
1.484
1.460
1.436
1.411
1.387
1.362
1.343
1.318
1.294
1.274
1.250
1.230
1.211
1.187
1.167
1.147
1.128
1.108
1.089
1.069
1.050
1.030
1.016
0.996
0.977
0.962
0.942
0.928
0.913
0.894
0.879
0.864
0.850
0.835
0.820
0.806
0.791
0.776
0.762
0.747
0.732
0.723
0.708
0.698
0.684
0.674
0.659
0.649
0.635

1. Overall accuracy for any of the sensors is at least + 2 F over the range shown. Accuracy of matched sensors is + 1 F over specific ranges.
2. As you compare a thermistor resistance (or input voltage) reading with the “actual” temperature indicated by the thermometer, be sure to
consider the precision and location of the thermometer when you decide whether or not the thermistor is out of specified accuracy.
3. The thermistor resistances given do not account for the self-heating effects that are present when connected to the UCM. A connected
“operating” thermistor will read a slightly lower (less than 1%) resistance.

RLC-SVD03A-EN

Temperature Sensor Checkout
Table 4
Sensor Conversion Data: Saturated Condenser and Entering Oil Temperature Matched Pairs
(6RT12, 3B1RT1; 6RT13, 4B1RT2)
Actual
Temp.
(F)

Actual
Resistance
(Ohms)

Thermistor
Voltage
(Volts DC)

Actual
Temp.
(F)

Actual
Resistance
(Ohms)

Thermistor
Voltage
(Volts DC)

Actual
Temp.
(F)

Actual
Resistance
(Ohms)

Thermistor
Voltage
(Volts DC)

0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.0
15.0
16.0
17.0
18.0
19.0
20.0
21.0
22.0
23.0
24.0
25.0
26.0
27.0
28.0
29.0
30.0
31.0
32.0
33.0
34.0
35.0
36.0
37.0
38.0
39.0
40.0
41.0
42.0
43.0
44.0
45.0
46.0
47.0
48.0
49.0

87510.3
84745.9
82072.1
79500.1
77012.3
74609.7
72288.8
70047.4
67881.9
65790.2
63768.7
61815.3
59927.8
58103.1
56339.6
54634.7
52986.4
51392.6
49851.6
48360.9
46919.2
45524.6
44175.6
42870.3
41607.6
40385.3
39202.7
38057.9
36950.0
35877.4
34838.9
33833.3
32861.4
31935.3
31038.7
30170.5
29329.5
28515.0
27725.9
26961.4
26220.8
25503.0
24807.5
24133.3
23479.7
22846.1
22231.9
21636.2
21058.7
20498.4

4.651
4.641
4.630
4.619
4.608
4.596
4.584
4.572
4.560
4.547
4.534
4.521
4.507
4.494
4.479
4.465
4.450
4.435
4.420
4.404
4.388
4.372
4.355
4.338
4.321
4.303
4.285
4.266
4.248
4.229
4.209
4.190
4.170
4.150
4.130
4.109
4.088
4.067
4.045
4.024
4.002
3.979
3.957
3.934
3.910
3.887
3.863
3.839
3.815
3.790

50.0
51.0
52.0
53.0
54.0
55.0
56.0
57.0
58.0
59.0
60.0
61.0
62.0
63.0
64.0
65.0
66.0
67.0
68.0
69.0
70.0
71.0
72.0
73.0
74.0
75.0
76.0
77.0
78.0
79.0
80.0
81.0
82.0
83.0
84.0
85.0
86.0
87.0
88.0
89.0
90.0
91.0
92.0
93.0
94.0
95.0
96.0
97.0
98.0
99.0

19955.0
19427.9
18916.5
18420.3
17938.8
17471.6
17018.0
16577.8
16150.5
15735.7
15332.9
14941.7
14561.9
14193.0
13834.6
13486.5
13148.3
12819.8
12500.5
12190.2
11888.7
11595.6
11310.7
11033.7
10764.4
10502.6
10248.0
10000.0
9759.6
9525.4
9297.5
9075.9
8860.2
8650.4
8446.2
8247.5
8054.1
7865.8
7682.5
7504.2
7330.5
7161.4
6996.7
6836.3
6680.1
6528.0
6379.8
6235.5
6094.8
5957.8

3.765
3.740
3.715
3.689
3.664
3.638
3.611
3.585
3.558
3.531
3.504
3.477
3.450
3.422
3.394
3.366
3.338
3.310
3.282
3.253
3.225
3.196
3.167
3.139
3.110
3.081
3.051
3.022
2.993
2.964
2.935
2.905
2.876
2.847
2.817
2.788
2.759
2.730
2.700
2.671
2.642
2.613
2.584
2.555
2.526
2.498
2.469
2.440
2.412
2.384

100.0
101.0
102.0
103.0
104.0
105.0
106.0
107.0
108.0
109.0
110.0
111.0
112.0
113.0
114.0
115.0
116.0
117.0
118.0
119.0
120.0
121.0
122.0
123.0
124.0
125.0
126.0
127.0
128.0
129.0
130.0
131.0
132.0
133.0
134.0
135.0
136.0
137.0
138.0
139.0
140.0
141.0
142.0
143.0
144.0
145.0
146.0
147.0
148.0
149.0
150.0

5824.3
5694.2
5567.4
5443.8
5323.3
5205.9
5091.5
4979.9
4871.1
4765.0
4661.5
4560.6
4462.2
4366.3
4272.6
4181.3
4092.2
4005.3
3920.5
3837.7
3756.9
3678.1
3601.1
3526.5
3453.6
3382.4
3313.0
3245.1
3178.9
3114.2
3051.0
2989.2
2928.9
2870.0
2812.4
2756.2
2701.2
2647.5
2595.0
2543.7
2493.6
2444.6
2396.7
2349.9
2304.1
2259.2
2216.0
2172.8
2131.6
2090.4
2051.2

2.356
2.327
2.300
2.272
2.244
2.217
2.189
2.162
2.135
2.108
2.082
2.055
2.029
2.003
1.977
1.951
1.926
1.901
1.876
1.851
1.826
1.802
1.777
1.754
1.730
1.707
1.684
1.661
1.638
1.615
1.593
1.571
1.549
1.528
1.506
1.485
1.464
1.444
1.423
1.403
1.383
1.364
1.344
1.325
1.306
1.287
1.269
1.250
1.232
1.215
1.197

1. Overall accuracy for the sensor is at least + 2 F over the range shown.
2. As you compare a thermistor resistance (or input voltage) reading with the “actual” temperature indicated by the thermometer, be sure to
consider the location and precision of the thermometer when you decide whether or not the thermistor is out of specified accuracy.
3. The thermistor resistances given do not account for the self-heating effects that are present when connected to the UCM. A connected
“operating” thermistor will read a slightly lower (less than 1%) resistance.

RLC-SVD03A-EN

Compressor Operation
This feature is called the Auto Lead/Lag and can be found in the Service
Settings Group, under the “Balanced CPRSR Starts and Hours” menu. When
this function is disabled, the UCM always starts compressor “A” first. When
this function is enabled, the following occurs:
The UCM equalizes operating starts and hours. This will cause the
compressor with the least amount of starts to be started first. When a
compressor starts, it is always started unloaded.
When a compressor is stopped, it shuts down in an unloaded state, unless
taken out by a manual reset diagnostic.
When the first compressor is brought on line, it attempts to meet the load by
staging on the step load solenoid and by pulsing the male slide valve load
solenoid. If one compressor cannot meet the load demand, the second
compressor is brought on line. It also attempts to meet the load demand by
staging on its step load solenoid and by pulsing its male slide valve solenoid.
When both compressors are running and both of their step load solenoids are
energized, the male load and unload solenoids on both compressors are
pulsed, thus modulating their respective slide valves to balance the load. The
UCM attempts to distribute the load evenly between the two compressors.
When the load drops off, the compressor with the most hours will always be
the first to unload and turn off. The anti-recycle timer is approximately 5
minutes from start to start. The minimum time between compressor
shutdown and restart is approximately 10 seconds, but only if the
compressor has been running over 5 minutes or longer prior to shutting down
on temperature. Otherwise, it is the remaining portion of the 5 minutes.

Restart Inhibit Timer
If compressor operation is interrupted by an extended (not momentary) loss
of power or a manual reset, there will be a two minute delay between the
power up or manual reset and the start of a compressor, assuming there is a
call for cooling. The timer is factory set at 2 minutes but can be field adjusted
from 30 seconds to two minutes in the Service Settings Group.

RLC-SVD03A-EN

Compressor Start/Stop
To start a compressor after either a “normal' shutdown, a Diagnostic reset, or
power-on-reset, the following sequence will occur:
1.

On a call for a compressor, the Restart Inhibit Timer will time out, if any
time remains.

2. The EXV is positioned to the initial closed start position. At the same
time, the unload solenoid is energized and the load solenoid is de-energized. Timing is determined by the time required to position the EXV
3. After the EXV is positioned:
•

the compressor is turned on

•

the compressor heater is de-energized

•

the saturated evaporator ref. temp. cutout ignore time is set, based on
the saturated condenser temperature. Prior to start, the condenser temperature approximates the ambient temperature.

•

the fan control algorithm is executed

To stop a compressor due to either the Stop button on the CLD or an
External/Remote “STOP”, the sequence shall be as follows:
1.

The unload solenoid is energized for 20 seconds and the load solenoid is
de-energized. The compressor continues to run for the remaining 20 seconds. This is defined as the RUN:UNLOAD mode.

2. The compressor and the fans are turned off. The crankcase heater is
energized.
3. The unload solenoid remains energized for 60 minutes after the compressor stops. The load solenoid is de-energized.
4. The EXV is closed. Closing begins at maximum speed when the compressor is turned off. (Max. speed is 25 steps per second, full stroke is
757 steps.
5. After 60 minutes, the unload solenoid de-energizes.
The RUN:UNLOAD mode is also used to stop a compressor due to normal
LWT control, Low Ambient Run Inhibit, or Freeze Avoidance.
A compressor stop due to any diagnostic will skip step 1 above and go
directly to step 2.

RLC-SVD03A-EN

Variable Speed
Inverter/Condenser Fan Control
When Fan Control and Variable Speed Fan (VSF) are set to Enable in the
Machine Configuration Menu, the UCM will control both the variable speed
fan and the remaining constant speed fans per the VSF Control Algorithm. If
VSF Control is disabled for a given circuit but Fan Control is enabled for the
machine, the circuit will perform normal constant speed fan control. The VSF
is enabled and operational, the control attempts to provide a 70 ± 5 psid
between the Condenser Pressure and the Evaporator Pressure (as derived
from the temperature sensor measurements).

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Variable Speed Fan (VSF) and Fan Staging Control

The VSF Inverter is commanded to a given speed by the UCM, using a PWM
(Pulse Width Modulated) signal (10V, 15mA, 10 Hz Fundamental) with a duty
cycle proportional to the desired voltage and frequency from the Inverter. The
UCM also controls power to the Inverter through a contactor. The Inverter
Contactor for the respective circuit is energized approximately 20 seconds
prior to compressor start on that circuit. The VSF Control algorithm runs on a
5-second interval and is limited to a commanded rate of change of no greater
than 40% of full speed per interval. The same algorithm that controls the

RLC-SVD03A-EN

Variable Speed Inverter/
Condenser Fan Control
speed will also cause constant speed fans to stage On and Off when the
inverter is commanded to full speed and minimum speed respectively. The
stage On (or Off) of a constant speed fan will occur if the inverter speed
command is at max (or min.) for three consecutive intervals (15 seconds).

Outdoor Air Temperature and Fan Control
Outdoor air temperature is used to provide a reasonable startup state. Using
this temperature, the algorithm automatically determines the number of
constant speed fans to turn on immediately at compressor start. The outdoor
air temperature sensor is also used to anticipate new states during normal
running to minimize pressure upsets. This anticipation is based on the staging
and unstaging of compressor steps at given leaving water temperatures. In
this way, precise airflow can be maintained, allowing for stable differential
pressures under part load and low ambient conditions.

VSF Inverter Fault
A fault signal will be sent to the UCM from the Inverter when it has gone
through a self-shutdown or if the output frequency of the Inverter is being
limited to less than 50% of the signal speed commanded by the UCM. Upon
receipt of the fault signal, the UCM shall attempt to reset the fault by sending
a 0 PWM command to the Inverter for a total of five seconds. The fault signal
will again be checked and repeated if still in fault. If four faults are detected
within one minute of each other, the power to the Inverter will be cycled off
for 30 seconds (through contactor control) and then re-powered. If the fault
still remains or occurs again within one minute, an IFW diagnostic occurs.
The UCM will remove power from the Inverter and attempt to run the
remaining constant-speed fans using normal constant-speed Fan Control
Algorithm. See page 80 for step-by-step troubleshooting procedure.

RLC-SVD03A-EN

Current Transformer
Each compressor motor has all three of its line currents monitored by torroid
(doughnut) current transformers. While the MCSP utilizes all three of the
signals, it only displays the maximum phase at any given time. These currents
are normalized with respect to the Rated Load Amps of the respective
compressor and thus are expressed in terms of % (percent) RLA. The
currents are “normalized” thru the proper selection of the Current Transformer, the setting of the Compressor Current Overload dip switch (SW2) on
the MCSPs, and the redundant programming of the decimal equivalent of
these settings in the Service Settings Group of the CLD. (The term
“Compressor Current Overload setting” is actually a misnomer. Instead the
setting should be thought of as an internal software gain that normalizes the
currents to a % RLA for a given CT and compressor rating. The true nominal
steady state overload setting is fixed at 132%). Refer to Tables 5 thru 9 for
setup details.
The current transformers provide the input for six basic functions of the
MCSP:
1.

Motor overload protection using a programmed “% RLA versus time to
trip” characteristic. Refer to Table 6 for details. The steady state “must
trip” value is 140% RLA and the “must hold” value is 125% RLA. The
MCSP will trip out the compressor. The appropriate diagnostic descriptions are then displayed in the CLD diagnostic section.

2. Verifying contactor drop-out. If currents corresponding to less than 12
±7% RLA are not detected on all three of the monitored compressor
phases within approximately 5 seconds after an attempted contactor
drop-out, the compressor will continue to be commanded Off, the Unload
solenoid will be pulsed, the EXV will be opened to its fullest position, and
the fans will continue to be controlled. This condition will exist until the
diagnostic is manually reset.
3. Loss of Phase Current. If the detection of any or all of the three motor
phase currents falls below 12 ±7% RLA for 2 ±1 seconds while the
branch circuit should be “energized”, the MCSP will trip out the compressor. The Phase Loss diagnostic, or the Power Loss diagnostic, will be displayed. Failure of a contactor to pull in will cause the Phase Loss
diagnostic. However when reduced voltage starting is employed, it may
take an additional 3 seconds to detect a phase loss at startup, as phase
loss protection is not active during the 3 second transition time.
4. Phase Rotation. Screw compressors cannot be allowed to run in reverse
direction. To protect the compressors, the phase rotation is detected by
the current transformers immediately at start up. If improper phasing is
detected, within 1 second of startup, the MCSP will trip out the compressor. The Phase Rotation diagnostics will be displayed. This function is not
sensitive to the current transformer's polarity.
5. Phase Unbalance. The MCSP will shut down the compressor if a phase
current unbalance is detected by the current transformers while the compressor is running. A 15% unbalance, if protection is enabled, will cause
the MCSP to trip out the compressor. The Phase Unbalance diagnostics

RLC-SVD03A-EN

Current Transformer
will be displayed. If this protection is disabled, a 30% phase unbalance
will still be in effect with the diagnostic code Severe Phase Imbalance
being displayed.
6. Current Limit. The MCSP will begin to unload its compressor as the
%RLA exceeds 120%. Further, the CPM will cause the compressors to
automatically unload when the Chiller Current Limit Setpoint is reached.
The Current Limit Setpoint is set in the Service Setting Group. Individual
compressor phase currents are averaged and added together to compare
to the Chiller Current Limit which is in terms of % Total of all of the
Compressor RLNs.
NOTE: The current transformers are NOT polarity or directionally sensitive.

CT and MCSP Compressor Current Input Checkout
Procedure

Check incoming 3-phase power for voltage within 10% of nominal per
Chiller nameplate.

2. Interrogate the CPM for all of the presently active diagnostic codes or the
historic diagnostic codes in the Diagnostics Menu. Narrow the problem
down to a particular compressor or contactor as noted above. Write down
all of the diagnostic codes stored in the diagnostic registers.
If there is any question as to which compressor or current transformer is
causing a problem, or simply to verify and “witness” the problem, an
attempt should be made to restart the chiller after clearing diagnostics.
The diagnostics can be cleared by entering the Diagnostics Menu and
stepping to the CLEAR DIAGNOSTICS display.
It is possible to “force” certain compressors to be the first or next compressor to stage on, using the “Compressor Test” feature in the Service
Tests Menu. The Leaving Water Temperature must, however, be above
the Chilled Water Setpoint by more than the “differential to start” setting,
in order to stage on the first compressor.
At startup, verify the appropriate contactor(s) pull-in. The “Compressors
On” menu item in the Chiller Report Group will indicate which compressor started approximately five seconds after the contactor pulls in. Note
the diagnostic(s) that results, then place the Chiller into the “Stop” mode
by depressing the Stop button on the CLD.

RLC-SVD03A-EN

Current Transformer
WARNING
Hazardous Voltage w/Capacitors!
Disconnect all electric power, including remote disconnects
before servicing. Follow proper lockout/tagout procedures to
ensure the power cannot be inadvertently energized. For variable
frequency drives or other energy storing components provided by
Trane or others, refer to the appropriate manufacturer’s literature
for allowable waiting periods for discharge of capacitors. Verify
with an appropriate voltmeter that all capacitors have discharged.
Failure to disconnect power and discharge capacitors before
servicing could result in death or serious injury.
Note: For additional information regarding the safe discharge of
capacitors, see PROD-SVB06A-EN or PROD-SVB06A-FR
3. For the next portion of the procedure, pull the unit's disconnect and interrupt all high voltage power to the control panel. Locate the torroid (doughnut) current transformers encircling the compressor power wiring and
branching to the compressor contactors of the suspect compressor-in the
control panel. Refer to the Component Location Drawing in the panel to
identify the particular current transformer(s) of interest. Locate the part
number/UL tag on the transformer leads and note the Trane part number
which identifies the transformers. Note: all compressors of a given tonnage should have the same transformer extension number. Verify the
proper current transformer using Table 5 in this section. Also check the
setting of the dip switch (SW2) on each of the MCSP modules and verify
these against Table 5 for each compressor. (Switch position SW2-1 is the
Most Significant Bit). The decimal equivalent of this setting should also
be verified in the Service Setting Group under the “CURRENT OVRLD
SETTINGS” display. If the programmed value does not agree with the dip
switch setting for each of the MCSP's, an informational diagnostic will
result. The compressors will be allowed to run, but default settings (the
most sensitive possible) will be used for the internal software compressor current gains.
4. Utilizing the Schematic Wiring Diagram, locate the termination of the
transformer's wiring into the MTA plug at the appropriate MCSP module
at pin header J5. Pull off the appropriate MTA connector from the pin
header on the MCSP.
Current Transformers can be damaged and high voltages can result due
to running the compressors without a suitable burden load for the CTs.
This load is provided by the MCSP input. Take care to properly reconnect
the CT's MTA prior to attempted start of the compressors.
5. Using a digital volt-ohmmeter, measure the resistance of the transformer(s) by probing the appropriate pair(s) of receptacles within the
MTA. The receptacle pairs of the MTA are most easily measured by using
meter leads with pointed probes and contacting the exposed metal of the
connector through either the top or the side of the MTA. (It may be necRLC-SVD03A-EN

Current Transformer
essary to remove a cap over the top of the connector to gain access to
the connector conductors.)
6. Refer to Table 7 which lists the normal resistance range for each extension of current transformer. Check the measured resistance against the
value listed per transformer extension. If the resistance is within tolerance, the transformer and MTA can be considered good. Go on to step 8.
7.

If the resistance reading above is out of tolerance, the problem is either
with the transformer, its wiring, or the MTA connector. First double check
the schematic to be sure you are working the proper lead pair. Then cut
the leads to the particular transformer near the MTA connector and
repeat the resistance measurement by stripping insulation from the
wire's end. Once the fault has been isolated in this manner, reconnect
leads or install a new transformer or connector.
More than one current transformer is terminated to a single MTA. When
replacing, take care to note the proper positions of the respective transformer wire terminations on the MTA for the re-termination. The current
transformers are NOT polarity or directionally sensitive. The transformer
lead wiring is #22 AWG, UL 1015 600V and the proper MTA connector
(red color code) must be used to ensure a reliable connection. If the fault
can be isolated to the current transformer or its wiring apart from the connector, the connector can be reused by cutting off the bad transformer
and splicing in a new transformer using wire nuts.

8. If the transformer/connector resistance proves accurate, recheck the
resistance with the connector held at different angles and with a light
lead pull (less than 5 lb.) to test for an intermittent condition.
9. To perform the following test, you will need to use a digital voltmeter with
a diode test function,. With the transformer MTA disconnected and the
power off to the MCSP, perform a diode test across the corresponding
pair of current transformer input pins on the MCSP (header J5). The
meter should read from 1.0 to 1.5 volts for each current transformer input.
Repeat using the opposite polarity. The same reading should result.
Extreme errors suggest a defective MCSP module. If the diode voltage
drops prove accurate, reconnect the transformers to the MCSP and
repower the unit.
10. With the CT's reconnected to the MCSP, attempt a restart of the chiller.
As the given compressor is started, and the inrush locked rotor transient
has passed, (locked rotor transient should last less than one second)
simultaneously monitor the actual compressor phase current(s) (using a
clamp-on type ammeter) and the voltage developed at the respective current transformer's termination at the MCSP (using a digital volt-meter on
a 0-20 VAC scale). Refer to Table 8 for the compressor phase current to
output voltage relationship for each extension current transformer. Using
Table 8, look up to current that corresponds to the output voltage read by
the voltmeter and compare to ammeter reading. Assuming relatively
accurate meters, the values should agree to within 5%.
11. If the measured current and the output voltage from the CT agree within
the tolerance specified, the CT is good. If diagnostics, overload trips, or
other problems potentially involving current sensing continue to occur
26

RLC-SVD03A-EN

Current Transformer
with all phase currents to the compressors verified to be within their normal range, then the problem is either with the CT selection, MCSP Compressor Overload Dip Switch Setting, or the MCSP's current input, analog
to digital (A/D), or dip switch input circuitry. Since the first two items
were verified in Step 2 using Table 5, that leaves only the MCSP circuitry
as an issue. It is advisable to replace the MCSP module at this point.
However if verification of the MCSP Current sensing operation is desired,
go to step 12 below.
12. There are two ways that the MCSP's current sensing can be checked.
Both methods use the CLD display of the %RLA from each MCSP (Compressor Report) for indication of the sensed current. The first is straightforward equation and assumes that the proper Compressor Overload dip
switch setting and current transformer have been selected:
Measured Compr. amps of max. phase
Nameplate Compressor RLA

%RLA = --------------------------------------------------------------------------------------------------------

To check the displayed % RLA as a function of the output voltage from the
current transformers (as connected at the MCSP), Tables 8 and 9 are utilized.
In Table 8 look up (or interpolate) the “% of CT rating” corresponding to the
maximum of the three CT Input Voltages (VAC rms) as read at the MCSP. (The
table is necessary because the voltage developed at the MCSP is not linear
with the CT's secondary current). Next, check the Compressor Current
Overload setting of switch SW2 on the MCSP and find the corresponding
“SOFTWARE GAIN” in Table 9. The % RLA displayed by the CPM should be:
%RLA = % CT Rating X SOFTWARE GAIN
The preceding equations should only be applied during steady state current
draws (after transition). Inrush transient currents and associated CT output
voltages can be expected to be from 3 to 6 times the steady state values, and
the displayed value only reads up to 255% RLA. The accuracy of the
displayed value should be within ± 5% of that predicted using the Input
voltage. However, the end to end accuracy of the displayed value compared
to the actual %RLA max. phase current is ± 3.3% over the range of 50 to
150% of CT rating.
13. If no phase currents are measured with the amprobe on any or all of the
legs to a given compressor immediately following the attempted staging
of that compressor by the MCSP, the problem lies either with the
contactor, motor circuit or the MCSP relay outputs. Refer to MCSP
Checkout Procedure in Compressor Module (MCSP) (1U4 AND 1U5) on
page 72.

RLC-SVD03A-EN

Current Transformer
Table 5

Compressor Overload DIP Switch Settings
Current
Transformer
Extension*

Overload Setting
Dip Sw/Decimal
12345**

-02

01011/11

-01

11111/31

-10

01100/12

Primary Turns
Through Current
Transformer

Compressor
Tons

Volts/Hz

200/60

115

230/60

100

346/50

RLA

380/60

-10

10000/16

400/50

-10

00000/0

460/60

-10

00000/0

575/60

-01

01111/15

200/60

142

-02

11011/27

230/60

124

-02

10001/17

346/50

-01

00111/7

380/60

-01

01010/10

400/50

-10

10001/17

460/60

-10

10001/17

575/60

-01

11111/31

200/60

192

-03

11100/28

230/60

167

-03

10010/18

346/50

-01

11100/28

380/60

101

-02

00001/1

400/50

-01

10011/19

460/60

-01

10011/19

575/60

-02

10111/23

200/60

233

-04

10011/19

230/60

203

-04

01000/8

346/50

117

-02

01101/13

380/60

123

-02

10001/17

400/50

101

-02

00001/1

460/60

101

-02

00001/1

575/60

-03

10000/16

*The current transformer base part number is X13580253. The numbers in this column are suffixes of the base part number.
**On the DIP switch, 1=ON, O=OFF. The decimal value should be set in the compressor overload setting menu of the UCM. If the
DIP switch value does not match the decimal value entered into the UCM, the related compressor(s) will continue to run, but a
diagnostic will be initiated, both settings will be ignored, and the UCM will use the lowest possible trip setting value.

RLC-SVD03A-EN

Current Transformer
Table 6

Trip Times Vs. % Current

MOTOR CURRENT
(% RATED RLA)

MINIMUM

TRIP TIME (SEC)
NOMINAL

MAXIMUM

127.7 or below
132.0
132.1
140.0 (must trip pt.)
150.0
160.0
170.0
180.0
190.0
200.0
210.0
220.0
230.0
240.0
250.0
260.0
270.0
280.0
290.0
300.0
300.1
310.2 or above

No trip
27.2
27.2
22.8
18.8
16.0
14.0
12.4
11.2
10.4
9.6
8.8
8.0
7.6
7.2
6.8
6.4
6.0
5.6
4.0
4.0
4.0

No Trip
No Trip
30.08
25.28
20.48
17.28
15.28
13.28
12.08
10.88
10.08
9.28
8.48
8.08
7.68
6.88
6.88
6.48
6.08
5.68
4.08
4.08

No Trip
No Trip
No Trip
28.09
22.89
19.29
16.89
14.89
13.29
12.09
10.89
10.09
9.69
8.89
8.49
7.69
7.29
6.89
6.89
6.49
6.49
4.49

Table 7

Current Transformers Ratings and Resistance
RATING
USABLE

RANGE

RESISTANCE
OHMS + 10%

100A

66.67 -100A

23.5

150A

35.0

200A

100 - 150A
134 - 200A

275A

184 -275A

67.0

400A

267 - 400A

68.0

50A

33.37 - 50A

11.5

75A

50 - 75A

17.0

EXT*

46.0

*The current transformer base part number is X13580253. The
numbers in this column are suffixes of the base part number.

RLC-SVD03A-EN

Current Transformer
Table 8

Compressor Phase Current vs. AC Input Voltage at MCSP
ACTUAL COMPRESSOR PHASE AMPS THRU CT

EXT
-01

EXT
-02

EXT
-03

EXT
-04

EXT
-05

EXT
-09

EXT
-10

TERMINAL
VOLTAGE
(V RMS)

% OF CT
RATING

0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300

0
8
15
23
30
38
45
53
60
68
75
83
90
98
105
113
120
128
135
143
150
158
165
173
180
188
195
203
210
218
225
240
255
270
285
300
315
330
345
360
375
390
405
420
435
450

0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
320
340
360
380
400
420
440
460
480
500
520
540
560
580
600

0
14
28
41
55
69
83
96
110
124
138
151
165
179
193
206
220
234
248
261
275
289
303
316
330
344
358
371
385
399
413
440
468
495
523
550
578
605
632
660
687
715
742
770
797
825

0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
400
420
440
460
480
500
520
540
560
580
600
640
680
720
760
800
840
880
920
960
1000
1040
1080
1120
1160
1200

0
2.5
5
7.5
10
12.5
15
17.5
20
22.5
25
27.5
30
32.5
35
37.5
40
42.5
45
47.5
50
52.5
55
57.5
60
62.5
65
67.5
70
72.5
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150

0
3.75
7.5
11.25
15
18.75
22.5
26.25
30
33.75
37.5
41.25
45
48.75
52.5
56.25
60
63.75
67.5
71.25
75
78.75
82.5
86.25
90
93.75
97.75
101.25
105
108.75
112.5
120
127.5
135
142.5
150
157.5
165
172.5
180
187.5
195
202.5
210
217.5
225

0.00
1.19
1.37
1.53
1.67
1.81
1.95
2.09
2.23
2.36
2.50
2.63
2.77
2.90
3.03
3.17
3.30
3.43
3.57
3.70
3.83
3.96
4.10
4.23
4.36
4.49
4.62
4.75
4.88
5.02
5.15
5.41
5.67
5.94
6.20
6.46
6.72
6.99
7.25
7.51
7.77
8.03
8.29
8.56
8.82
9.08

0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300

RLC-SVD03A-EN

Current Transformer
Table 9

RLC-SVD03A-EN

Overload Dip Switch Setting vs. Internal Software Gain

CPRSR RATED RLA
AS A % OF CT RATING

OVERLOAD DP
SWITCH SETTING

DECIMAL
SETTING

SOFTWARE
GAIN

66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100

00000
00001
00010
00011
00100
00110
00111
01000
01001
01010
01011
01100
01101
01111
01111
10000
10001
10010
10011
10100
10101
10110
10110
10111
11000
11001
11001
11010
11011
11100
11100
11101
11110
11110
11111

00
01
02
03
04
06
07
08
09
10
11
12
13
15
15
16
17
18
19
20
21
22
22
23
24
25
25
26
27
28
28
29
30
30
31

1.500000
1.483870
1.467743
1.451613
1.435483
1.403226
1.387097
1.370969
1.354839
1.338709
1.322580
1.306452
1.290323
1.258065
1.258065
1.241936
1.225806
1.209678
1.193549
1.177419
1.161291
1.145162
1.145162
1.129032
1.112903
1.096775
1.096775
1.080645
1.064516
1.048387
1.048387
1.032258
1.016128
1.016128
1.000000

Under-Over Voltage Transformer
The hardware required for the Under/Over voltage sensing function of the
UCM is standard on the 70-125 Ton RTAA chiller. This feature must be
Enabled in the Service Settings Menu for it to be active. A custom designed
transformer whose primary is connected across the Line Voltage phases A to
B, provides a stepped down and isolated AC voltage to the CPM at input J4.
This secondary voltage is directly proportional to the line voltage applied to
the primary. The Chiller Report on the CLD can directly display the % Line
Voltage and, when so enabled, can cause automatically reset MAR
diagnostics for High and Low Line condition. The % Line Voltage is internally
calculated by dividing the selected nominal voltage rating (only certain
discrete values are selectable in the Service Settings Group) by the actual line
voltage as read and processed by the CPM. With the Under-Over Voltage
Protection Function enabled, an Over Voltage diagnostic will occur if the
calculated % Line Voltage equals or exceeds 114%, or an Under Voltage
diagnostic will occur if it equals or falls below 87% for 15 continuous
seconds. Reset differential is set at 3%.

Under-Over Voltage Transformer Checkout

Locate the Under-Over Voltage Transformer [1T2] in the panel by referring
to the Component Location Drawing. Carefully measure the primary voltage across the Transformer (Line Voltage Phase A to B) and note the
value in Vac rms.

2. Next disconnect the transformers secondary from J4 on the CPM. Using
voltmeter probes, measure and note the unloaded secondary voltage
(Vac rms). (low voltage class 2 less than 32 Vac).
3. The ratio of the primary or line voltage to the open circuity secondary
voltage should be 20 to 1. If the unloaded turns ratio is not within ±2% of
this value, replace the transformer.
4. Reconnect the secondary back to J4 and remeasure the loaded (connected) secondary voltage. The new loaded ratio should be approximately
20.2 to 1. If not within ±2% of this ratio the transformer's secondary
should be disconnected from the CPM and a 1 Kohm resistor connected
across the secondary. Measuring the voltage across the 1 Kohm resistor
should give us a voltage ratio of 20.17. Ratios more than ±2% in error suggest a bad transformer. If the 1 Kohm loaded ratio is within tolerance, but
the CPM connected ratio is out of tolerance suspect a bad CPM. Before

RLC-SVD03A-EN

Under-Over Voltage Transformer
replacing the CPM, double check the Under-Over Voltage Function's
Nominal Line Voltage Setup in the Service Settings Group.
5. If the Under-Over Voltage Protection function continues to misoperate,
and all of the above measured ratios are within tolerance, and all CLD
Under Over Voltage setups have been verified, replace the CPM. It is a
good idea, before replacing the CPM, however, to copy down all of setup
data. This data will be very helpful in making the necessary setup on the
replacement CPM.

RLC-SVD03A-EN

Compressor Capacity
The 35 to 60 ton helical rotary screw compressors are loaded and unloaded
by means of an internal slide valve and a female unloader valve. In simple
terms, these valves can regulate the amount of “bite” of the compressor
rotors as they turn at relatively constant speeds.
The slide valve is moved by a hydraulic cylinder and piston internal to the
compressor (the hydraulic fluid is oil from the refrigerant system). The
movement of the cylinder is controlled by the load and unload solenoid
valves, which either add oil at compressor discharge pressures, or withdraw
oil to suction pressures.
The female unloader valve is moved to either the On or Off position by using
internal suction and discharge gas pressure. The movement of this valve is
controlled by the female unloader valve solenoid. These solenoid valves are
electrically controlled by the MCSP module to handle compressor startup and
shutdown, maintain chilled water temperature setpoints and limit current,
condenser pressures, and evaporator temperatures etc.
Although the solenoids are an “on - off” device, effective modulation and high
resolution of the slide valve (under steady state conditions) is possible by
pulsing on and off the solenoid valves and varying the displaced volume of
the cylinder/piston. When a given compressor is operating, the MCSP will
energize (apply 115 VAC) either the load or the unload solenoid, if necessary,
for a period of between 40 and 400 milliseconds, once every 10 seconds to
control water temperature or limit conditions.
The female unloader valve solenoid receives a constant signal from the UCM
as the first step in compressor loading and the last step in compressor
unloading. Just prior to and just after a compressor start, and just before a
compressor stop, the MCSP will continuously energize the unload solenoid
for 20 to 30 seconds to assure unloaded starts. After a compressor stop, the
unload solenoid valve will remain energized for approximately one hour to
prevent slide valve movement due to changing cylinder/compressor
pressures.
The first procedure below will allow the checkout of the MCSP load and
unload outputs. The next procedure will allow the checkout of the Load and
Unload Solenoid valves located on the compressor as well as the operation of
the Slide Valve modulating unloader. Lastly, the female unloader valve and
solenoid will be discussed.

RLC-SVD03A-EN

Compressor Capacity
Checkout Procedure for MCSP Load/Unload Outputs

WARNING
Live Electrical Components!
During installation, testing, servicing and troubleshooting of this
product, it may be necessary to work with live electrical
components. Have a qualified licensed electrician or other
individual who has been properly trained in handling live
electrical components perform these tasks. Failure to follow all
electrical safety precautions when exposed to live electrical
components could result in death or serious injury.
The MCSP controls the Load and Unload Solenoid valves on the respective
compressor with 115 V triacs (solid state relays). Unlike mechanical relays
however, a triac has a rather high leakage current when off, comparatively
speaking. While this leakage is not nearly enough to actuate a solenoid valve,
it may, under no load conditions (as would be experienced when a solenoid
coil failed open), look like it was stuck “on” when using a voltmeter to test it.
Thus it is important to verify that the solenoid coil is continuous and providing
a normal load or to connect a known good load, such as a low wattage 115
Volt lamp, to the terminals when testing the outputs. Refer to the Chiller
Control Wiring diagrams and Component Location Drawings for the following
procedure.
With the particular compressor running, the triacs may be checked (under
load as explained above) by measuring the voltage from terminals E7 or E8 to
115 neutral. The triacs operate in the high side and switch 115 Vac power from
J7-1 to either E7 (load solenoid) or E8 (unload solenoid) to move the slide
valve in the appropriate direction. Except during compressor starts and stops,
in normal operation, the solenoid valves can only be energized for a period of
between 40 and 400 milliseconds once every 10 seconds. Often, if the chilled
water setpoint is being met under steady state conditions, they may not
energize at all. To assure loading and unloading is occurring it may be
necessary to make slight adjustments to the chilled water setpoints to force
action. As the pulsed on-time is potentially short it may be difficult to see,
especially if using a meter movement type voltmeter. (Use of a low wattage
115 Vac test lamp may be of some help for a visual indication of output triac
operation.)
When a triac is off, about 0 Vac should be measured on its terminal with the
solenoid load connected. When it is on, the voltage should be close to 115
Vac (the drop across the triac is about 1-2 volts).
The best time to check the unload solenoid is immediately after a power-up
reset of the MCSP. For the first 30 seconds after applying power the unload
solenoid should be on continuously. The next best time to check it is after the
compressor starts. For the first 30 seconds after a start the unload solenoid
should be on continuously.
Checking the load solenoid is more difficult. 30 seconds after a start, the
compressor will usually start loading, until water temperatures are satisfied.
Remember however, that under certain limit conditions, the MCSP may
RLC-SVD03A-EN

Compressor Capacity
prevent a compressor from loading even if the chilled water setpoint is not
satisfied. Refer to the RTAA-IOM-4 for discussion on condenser, evaporator,
and current limiting functions and setpoints. Refer to the Mode display under
the Chiller Report on the CLD for an indication of the current running mode.

Checkout Procedure for the Slide Valve and Load/
Unload Solenoids
Make sure unit is off and there is no power in the control panel before
beginning this procedure.
Setup
1. Identify the MCSP Module associated with the compressor to be tested
(1U4 or 1U5). Disconnect the stake-on terminals for the Load and Unload
Solenoid Valves at the MCSP UCM (E7 and E8 respectively) but take care
to identify the wires so as to prevent crosswiring when reconnecting.

WARNING
Hazardous Voltage w/Capacitors!
Disconnect all electric power, including remote disconnects
before servicing. Follow proper lockout/tagout procedures to
ensure the power cannot be inadvertently energized. For variable
frequency drives or other energy storing components provided by
Trane or others, refer to the appropriate manufacturer’s literature
for allowable waiting periods for discharge of capacitors. Verify
with an appropriate voltmeter that all capacitors have discharged.
Failure to disconnect power and discharge capacitors before
servicing could result in death or serious injury.
Note: For additional information regarding the safe discharge of
capacitors, see PROD-SVB06A-EN or PROD-SVB06A-FR
2. Install a toggle switch between Control Power HOT (1TB3-8 or 9) and the
Load and Unload Solenoid Valve leads (previously connected to E7 and
E8). Initially make sure that the Load toggle switch is open and the
Unload toggle switch is closed.
3. Install a pressure gauge with a refrigerant hose (hose should be long
enough to read the gauge from the control panel) to the slide valve piston/cylinder cavity Schrader valve located near the load/unload solenoids.
4. Reapply power to the unit and place the chiller in the “Stop” mode. Using
the CLD, select and enable the “Compressor Test” (in the Service Tests
Menu) for the compressor that is to be run. Additionally, to prevent the
opposite refrigeration circuit from running, if desired, the circuit can be
locked out through the CIRCUIT LOCKOUT display in the Service Tests
Menu for the appropriate circuit. Next place the Chiller into the “Auto“
mode and provide all necessary interlocks and a load (or adjust chilled
water setpoint) to start the chiller. The selected compressor will be the
first to stage on (after the restart inhibit timer has expired).

RLC-SVD03A-EN

Compressor Capacity
NOTE: Enabling the “Compressor Test” only affects which compressor will
be cycled on next and is not an override mode. The chiller will continue to
operate normally (not withstanding circuit lockout) and will stage
compressors on and off, as well as attempt to modulate running compressors
to maintain chilled water setpoint. Be aware that during manual control of the
load/unload solenoids, as explained in item 6, below, other compressors may
stage and/or attempt to modulate and thus will affect the leaving chilled water
temperature. However, all diagnostics are still active. No specific action, other
than reconnecting the solenoid valves to their respective outputs on the
MCSP, is required to return the Chiller to normal operation.
5. Allow the compressor to start and monitor compressor currents either in
the Compressor Report display (maximum phase % RLA) or with a
clamp-on type ammeter.
Load
1. Once the compressor has started, allow the Unload Solenoid Valve to
remain energized for approximately 30 seconds, then open the Unload
toggle switch to de-energize the valve. Verify that at least one condenser
fan is on before continuing with the checkout, as low differential refrigerant pressures will preclude proper Slide Valve operation. Record the cylinder cavity pressure and the compressor currents.
2. Manually close and open the Load toggle switch, to energize the Load
Solenoid, in 4 or 5 short “pulses”. Each load pulse should be approximately one second in duration, with approximately 10 seconds between
pulses.
NOTE: Loading the compressor faster than this rate could cause control
instability and possible diagnostics. Leave the toggle switch open, i.e., valve
de-energized.
3. If the %RLA or the current and pressure increases,' then the Load Solenoid and Slide Valve are operating properly.
4. If the %RLA or current does not increase, read the pressure at the cylinder cavity; Pressure increases, to approximately condenser pressure
(condenser pressure read via the CLD) without an increase in % RLA
(unless already fully loaded), indicate the Slide Valve is bound.
5. If cylinder cavity pressure does not increase, check the coil of the Load
Solenoid.
6. If the coil checks out, then one of two problems exist. Either the Load
Solenoid Valve is malfunctioning or the Unload Valve is stuck open.
NOTE: Refer to the flow chart shown in Figure 5.

RLC-SVD03A-EN

Compressor Capacity
1.

Install toggle switches across load and unload solenoid

2.
3.

Install Pressure Gage on slide valve piston/cylinder cavity Schrader valve.
Start Unit.

Load:
4.

Manually load compressor in short increments.

Does RLA increase?

Yes

Check UCM

Good

Bad

Repeat
procedure
for unload

Replace

Does Cavity Press
increase to a level close
to discharge pressure?

Yes

Slide valve mechanism bound

Does Magnetic Field on
Solenoid Coil exist?

Yes

Solenoid valve mechanism bound
or unloader valve stuck open

Is wiring to valve OK?

Yes

Check for open solenoid coil

Repair and reverify.

Figure 5

Manual Slide Valve Diagnostic Flow Chart - Load

Unload
NOTE: The following assumes that the compressor's slide valve is already
at some loaded position and %RLA is higher than the minimum noted in step
1.
1.

Manually close the Unload toggle switch to continuously energize the
Unload Solenoid Valve.

2. If the %RLA decreases, then the Unload Valve and Slide Valve are operating properly.
3. If the %RLA does not decrease, observe the cylinder cavity pressure
reading.
4. If cylinder cavity pressure reading decreases to approximately the suction
38

RLC-SVD03A-EN

Compressor Capacity
pressure, then the Slide Valve is bound.
5. If cylinder cavity pressure does not decrease or is at suction pressure
before the Unload toggle switch was closed, the problem lies with either
the solenoid coil or valve.
6. Check coil
7.

If coil checks out, change the valve.

NOTE: Refer to the Flow Chart in Figure 6.
Unload:
10. Manually unload compressor in short increments.
Yes

11. Does RLA Decrease?

Check UCM

Good

Stop

Bad

Replace

12. Does Cavity Press
decrease to a level
close to suct pressure?

Yes

Slide valve mechanism bound

13. Does Magnetic Field on
Solenoid Coil exist?

Yes

Solenoid valve mechanism bound

14. Is wiring to valve OK?

Yes

Check for open solenoid coil

15. Repair and reverify.

Figure 6

Manual Slide Valve Diagnostic Flow Chart

Checkout Procedure for MCSP Step Load Output
The MCSP controls the step load solenoid valve on the respective
compressor with a 115 VAC dry contact output relay. This differs from the
Load/Unload solenoid output, which is from a triac (solid state relay). Refer to
the Chiller Control Wiring diagrams and the Component Layout Drawings for
the following procedure.
RLC-SVD03A-EN

Compressor Capacity
WARNING
Live Electrical Components!
During installation, testing, servicing and troubleshooting of this
product, it may be necessary to work with live electrical
components. Have a qualified licensed electrician or other
individual who has been properly trained in handling live
electrical components perform these tasks. Failure to follow all
electrical safety precautions when exposed to live electrical
components could result in death or serious injury.
With a particular compressor running, the relay may be checked (under load,
as explained above) by measuring the voltage from terminal J7-9 to the 115
VAC neutral. The relay operates in the high side and switches power from
J7-8 to J7-9, to move the step load valve to the loaded position. When the
CPM decides to load the compressor, the step load solenoid is energized
continuously. To assure that loading and unloading is occurring, it may be
necessary to make slight adjustments to the chilled water setpoints to force
action.

Checkout Procedure for Step Load Solenoid Valve
and Piston
Prior to a compressor start, connect a pressure gauge to the Schrader port
near the step load solenoid valve. This port is connected to the back side of
the step load piston and, therefore, will allow direct measurement of the
pressure that actuates the step load valve. Observe the pressure gauge
during a compressor start, either from a manual compressor test or a normal
call for cooling. Initially, the pressure should drop to the suction pressure and,
when the MCSP calls for compressor loading, the solenoid will actuate and
supply discharge pressure to the piston. If, after verifying that 115 VAC has
been applied to the step load solenoid, the pressure does not increase to
discharge pressure, the step load solenoid coil and/or valve must be replaced.
Also, when the solenoid valve is energized and the piston pressure is near
discharge pressure, the percent RLA of the compressor, as seen in the
Compressor Report, should increase. If the percent RLA does not increase,
the step load valve is stuck and should be repaired.

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
This section will detail the normal voltage levels present on each of the
modules inputs and outputs under various conditions or states. Typical
operation of the I/O will be discussed in terms of chiller operation. This should
help the serviceman determine when and how they should function. Certain
inputs have been presented in greater detail in earlier sections and these are
referenced where applicable.

Power Supply
All of the modules are powered from 115 VAC 50/60hz Control Power except
the CLD and the IPCB, which are powered by 24 VAC. This power is provided
by either a control power transformer or is customer supplied. With the
exception of the CLD, LCI-C and the IPCB modules, the other modules have
incoming power connected to the upper-most terminal on the right hand side
of the module, just below the fuse. The terminal is arranged with two hot
pins (1 and 2), a keying pin (3), and two neutral pins (4 and 5), for ease of
“daisy chaining” power from one module to another. Incoming power can be
verified by measuring the voltage between the fuse bottom (hot side) and the
connector's neutral (pins 4 or 5). The voltage should read between 97.8 to
132.2 volts AC rms. Refer to Figure 7. (The ±15% voltage criteria is most
important for the EXV module's operation, as the Electronic Expansion
Valve's available torque is directly related to this value).
The fuses can be checked by looking for the supply voltage at the top of the
fuse (fused side) with respect to the connector neutral.
If some modules have power and some do not, the “daisy chain” wiring or
power connections should be suspected. Refer to the Unit Wiring diagrams
for the specifics on the power wiring.
Generally a power loss to a particular module will first be noticed as a
communications loss with that module. The module can be identified by
analysis of the IPC diagnostics as displayed by the CPM. Refer to Section 2
Interprocessor Communication for more information about Communication
(IPC) diagnostics. If the CLD's display is blank, 24 VAC power should be
checked at the CLD.

RLC-SVD03A-EN

Module Power and Miscellaneous I/O

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AC Power Connection To Modules

Clear Language Display (CLD) 1U6 Keypad Overview
Local operator interface with the system is accomplished using the 16 keys
on the front of the Clear Language Display panel. The readout screen is a two
line, 40 character liquid crystal display with a backlight. The backlight allows
the operator to read the display in low-light conditions. The depression of any
key will activate the backlight. The backlight will stay activated for 10 minutes
after the last key is pressed. At 10 F or below the backlight will stay activated
continuously.
The keys are grouped on the keyboard by the following functions (refer to
Figure 8):
- Select Report Group
- Select Settings Group
- Selection Keys
- Stop & Auto Keys

RLC-SVD03A-EN

Module Power and Miscellaneous I/O

Figure 8

Operator Interface Adaptive Control

Select Report Group
This group of four keys allows the operator to select and view the following
reports:
- Custom Report
- Chiller Report
- Refrigerant Report
- Compressor Report
The Custom Report is the only report of the four that is defined by the
operator. Any display under the other three reports can be added to the
Custom Report by pressing the plus
key while the desired read-out is on
the display. A maximum of 20 entries can be contained under the Custom
Report. Items can be deleted from the Custom Report by pressing the minus
key when the desired read-out is on the display. The operator must be in
the Custom Report menu to delete the desired item.
The Chiller Report, Refrigerant Report and Compressor Report are informational reports that give current status. Each report and its contents are
discussed in detail on the following pages.

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
When any of the four report keys are pressed, the first readout on the display
will be the header. The header identifies the title of the report and summarizes the items in the report.
The Next key and Previous key allow the operator to scroll up and down
through the display items listed under the report menus. When the last item
of a report is displayed and the Next key is pressed, the display will wrap
around to the header of the report. When the first item of a report is
displayed and the Previous key is pressed, the display will wrap around to the
last item.
Select Settings Group
The first three keys on the second row - Operator Settings, Service Settings
and Service Tests - allow the operator to adjust various setpoints and perform
various tests. Certain items in these groups are password protected. Refer to
the Password section for additional information.
When a setpoint key is pressed, a header will be displayed. The setpoint
headers identify the available items and setpoint functions.
The Next and Previous keys function in the same manner as that described in
Selected Report Group, above.
Setpoint values are incremented by pressing the Plus
key and decremented by pressing the Minus
key. Once a setpoint is changed, the Enter
key must be pressed to save the new setpoint. If the Cancel key is pressed,
the setpoint value on the display will be ignored and the original setpoint will
remain.
Passwords
Passwords are needed to enter into the Service Setup Menu and the
Machine Configuration Menu. Both of these menus are accessed through the
Service Settings key. If access into these menus is necessary, follow the list
of steps below:
1.

Press Service Settings

2. Press Next until the readout in the display is:
Password Required For Further Access “Please enter Password”
3. To enter into the Service Setup Menu, press:

Enter

4. To enter into the Machine Configuration Menu, press:

Enter

Refer to RTAA or RTWA IOM for the list of items found in the Service Setup
Menu and Machine Configuration Menu.
Select Report Group and Select Settings Group Flowcharts
Refer to RTAA or RTWA IOM for the display readouts found under each
menu. The first block of the flowchart is the header which is shown on the
display after the menu key is pressed. For example:
Press Chiller Report and the readout on the display will be
CHILLER RPRT:STATUS, WTR TEMPS & SETPTS
“PRESS (NEXT) (PREVIOUS) TO CONTINUE”

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
Press Next to move down through the Chiller Report. As shown in the
figures, the flowchart explains the conditions that the UCM looks at to
determine which readout is to be displayed next. For example:
Press Chiller Report to display the header
Press Next to display
MODE:

[OPERATING MODE]

REQUESTED SETPOINT SOURCE:

[SETPT SOURCE]

Press Next to display
COMPRESSOR ON
CIRCUITS LOCKED OUT
Press Next to display
ACTIVE ICE TERMINATION SETPOINT
or
ACTIVE CHILLED WATER SETPOINT
The UCM will determine which screen will be displayed after looking at the
current Operating Mode. If the Operating Mode is “Ice Making” or “Ice
Making Complete”, ACTIVE ICE TERMINATION SETPOINT will be displayed.
Otherwise, ACTIVE CHILLED WATER SETPOINT will be shown.
The flowcharts also list the setpoint ranges, default options and a brief
description of the item, when necessary. This information is shown in the
lefthand column of the page, adjacent to the appropriate display.
Auto/Stop Keys
The chiller will go through a “STOPPING” mode when the Stop key is
pressed, if a compressor is running. This key has a red background color
surrounding it, to distinguish it from the others.
If the chiller is in the Stop mode, pressing the Auto key will cause the UCM to
go into the Auto/Local or Auto/Remote mode, depending on the Setpoint
Source setting. The Auto key has a green back-ground color.
When either the Auto or Stop key is pressed, Chiller Operating Mode (Chiller
Report Menu) will be shown on the display.
Power Up
When power is first applied to the control panel, the Clear Language Display
goes through a self-test. For approximately five seconds, the readout on the
display will be
SELF TEST IN PROGRESS
During the self-test, the backlight will not be energized. When the tests are
successfully complete, the readout on the display will be
6200 xxxx-xx

[TYPE] configuration

Updating Unit Data, Please Wait

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
When updating is successfully completed, the system will default to the first
display after the Chiller Report header:
MODE:

OPERATING MODE]

REQUESTED SETPOINT SOURCE:

[SETPT SOURCE]

and the backlight will be activated.

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TB1-1,2

IPC Communications

19.2K Baud serial data
5 V signal level
Refer to Interprocessor Communication (IPC)

TB2-1,2

24 VAC Power

18-30 VAC, neither side grounded

Figure 9

CLD Module (1U6)

LEDs
There are four LEDs located to the right of TB1 of the CLD module. See
Figure 9. The ST LED should be on continuously. If it blinks, it indicates the
processor is repeatedly being reset. The +5 VDC LED should also be on
continuously. It will go out if power drops below normal operating voltage.
The TX LED should blink every second or two, as the CLD transmits on the
IPC. The RX LED should blink continuously, indicating that other modules are
communicating.

Chiller Module (CPM) (1U1)

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
Test Points
There are two test points associated with the CPM module. They are easily
read with a DC voltmeter by probing the PC board solder pads found in the
upper left hand corner of the module. The positive meter lead should be
connected to the pad while referencing the negative meter lead to the board
edge ground plane.
NOTE: Don't use the aluminum module enclosure as a reference as it has
an anodized surface with insulating properties.
The DC voltages shall be within the tolerance specified below. If not replace
the module.
TP1: + 5 volts DC ± 5%
TP2: +12 volts DC ± 5%

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
° TP1 + 5V
° TP2 +12V

Figure 10

TB3-1

— CHILLED
WATER FLOW
— SWITCH

H
I
G
H
V
0
L
T
A
G
E

J1-4
J1-3
J1-2
J1-1

NO
NO

J2-2
J2-1

TB3-2

OUTDOOR AIR —
TEMP
—

TB1-1
TB1-2

TB3-3

EMERGENCY —
STOP
—

TB1-3
TB1-4

TB3-4

— EXTERNAL
AUTO/STOP
— INPUT

NNS —
NNS —

TB1-5
TB1-6

TB4-1
TB4-2
TB4-3

— COM ALARM
— (NO) RELAY
— (NC)

CEWT —
CEWT —

TB2-1
TB2-2

CLWT —
CLWT —

TB2-3
TB2-4

L
0
W

I
N
P
U
T
S

— 115V H
— 115V H
— KEY (N/C)
— 115V N
— 115V N

IPC (+) —
IPC (-) —
IPC (+) —
IPC (-) —
MANUF.
USE ONLY

V
0
L
T
A
G
E

J5-1
J5-2
J5-3
J5-4
J5-5

NOT USED

{
{

EVAP ENTERING —
WATER TEMP —

J3-5
J3-4

KEY

J3-3

EVAP LEAVING —
WATER TEMP —

J3-2
J3-1

AUX TEMP —
KEY (N/C)
AUX TEMP —

J6-3
J6-2
J6-1

U/O VOLT TRANSF —
KEY
U/O VOLT TRANSF —

J4-3
J4-2
J 4-1

TB4-4
TB4-5

— COM COMPR
— (NO) RUN
RELAY

I
N
P
U
T
S

— COM MAX CAPACITY 0
— (NO) RELAY
U
T
TB4-8 — COM EVAP PUMP
P
TB4-9 — (NO) RELAY
U
T
TB4-10 — COM SPARE
S
TB4-11 — (NO) RELAY
TB4-6
TB4-7

CPM (Chiller) Module (1U1)

I/O terminals
For the checkout of the I/O, refer to the block diagram of the module in Figure
10 and the Chiller Wiring Diagrams for both high and low voltage circuits. All
voltages are measured differentially between terminal pairs specified unless
otherwise indicated. The first terminal in the pair is the positive (or hot)
terminal. Voltages given are nominals and may vary by ±5%. Unregulated
Voltages (unreg) or 115 VAC voltages may vary by ±15%.

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
Table 16

CPM (Chiller) Nominal Terminal Input and Output (1U1)

Terminal
Designation

Description
of Circuit

Normal Terminal Voltages
for Various Conditions

J1-4 to 3 to CLD
J1-2 to 1 to 1U5

IPC Communications

19.2 kbaud serial data, 5 volt signal level.
Refer to Interprocessor Communication ([PC)

J2-2, 1

Manufacturing Address Use Only

+5 VDC No connection intended.

TB1-1, 2

Outdoor Air Temperature

Refer to Temperature Sensor Checkout

TB1-3, 4

Emergency Stop

open: 20.6 VDC unreg: Stopped
closed: 0 VDC: Normal
Must be jumpered if this feature is not used.

TB1-5, 6

NNS (Not Used)

open: 20.6 Vdc unreg: Normal
closed: 0 VDC: Setback

TB2-1, 2

ECWT (Not Used)

N/A

TB2-3, 4

LCWT (Not Used)

N/A

J3-5, 4

Entering Evaporator Water Temperature

Refer to Temperature Sensor Checkout

J3-2, 1

Leaving Evaporator
Water Temperature

Refer to Temperature Sensor Checkout

J4-3, 1

Under/Over Voltage
Transformer Input

Refer to Under/Over Voltage Transformer
Checkout Procedure

J5-1 or 2
to J5-4 or 5

Input Power

115 VAC, Power Supply on page 41.

J6-3, 1

Auxiliary Temp. Input

Refer to Temperature Sensor Checkout

TB3-2, 1

Chilled Water
Flow Switch Input

open: 115VAC: No Flow
closed: < 5VAC: Flow (Software imposes a 6 second delay
to respond to opening or closing.

TB3-3,4

Chilled Water Demand Switch and
External Auto Stop

open: 115VAC: Stop
closed: < 5VAC: Auto

TB4-1, 2

Chiller Alarm or Alarm Ckt 1
(N.O. Contact)

Dry SPDT Contact closes on Alarm, intended for 115 VAC
customer control circuit.

TB4-1, 3

Chiller Alarm or Alarm Ckt 1
(N.O. Contact)

Dry SPDT Contact opens on Alarm, intended for 115 VAC
customer control circuit.

TB4-4, 5

Unit Running, Alarm Ckt 2, or
Ckt 1 Running
(N.O. Contact)

Dry SPDT Contact closes on Unit Running,
Alarm Ckt 2 or Ckt 1 Running, intended for
115 VAC customer control circuit.

TB4-6, 7

Maximum Capacity or Ckt 2 Running
(N.O. Contact)

Dry SPDT Contact closes on Maximum Capacity or Ckt 2
Running, intended for 115 VAC customer control circuit.

TB4-8, 9

Chilled Water Pump Starter
(N.O. Contact)

Dry SPST Contact closes when Chilled Water
Demand Switch is closed, opens after time
delay specified in UCM 115 VAC customer control circuit.

TB4-10, 11

Spare Relay}
(N.O.) Contact

Dry SPST contact. 115 VAC customer control circuit.

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
Options Module (CSR) (1U2)

WARNING
Live Electrical Components!
During installation, testing, servicing and troubleshooting of this
product, it may be necessary to work with live electrical
components. Have a qualified licensed electrician or other
individual who has been properly trained in handling live
electrical components perform these tasks. Failure to follow all
electrical safety precautions when exposed to live electrical
components could result in death or serious injury.
Test Points
There are three test points associated with the CSR module. They are easily
read with a DC voltmeter by probing the PC board solder pads found in the
upper left hand corner of the module. The positive meter lead should be
connected to the pad, while referencing the negative meter lead to the board
edge ground plane.
Note: don't use the aluminum module enclosure as a reference as it has
an anodized surface with insulating properties. The DC voltages shall be
within the tolerance specified below. If not replace the module.
TP1: + 5 volts DC ±5%
TP2: + 6 volts DC ±5%
TP3: +12 volts DC ±25%
Switch SW-1
Switch SW1 is used to configure the External Chilled Water Setpoint input
and the External Current Limit Setpoint input for either a 2-10VDC, or a 420ma signal. With the respective switch closed (on), a shunt resistor is
switched into the input circuit to provide a fixed low value input impedance
(499 ohms) for current loop operation. With the switch off, the input
impedance is differentially 40Kohms.
External Setpoint Inputs (4-20ma/2-10VDC)
The chiller setpoint source should always be set to LOCAL when using any
external inputs, except a Tracer. When using a Tracer, always set the chiller
setpoint source to the Tracer mode. The setpoint source can be found in the
Operator Settings Menu.
These inputs accept either an isolated 4-20mA or 2-10VDC signal from an
external controller or programming resistor connected to an internal +5V
source. The switches SW1-1 and SW1-2 are used to select either the voltage
or current option for External Chilled Water Setpoint and External Current
Setpoint respectively. See Test Points, above. Alternately, either input may be
used with a resistor or potentiometer.
NOTE: Note: For proper operation, the 4-20mA/2-10VDC inputs are required
to be used with a current or voltage source that:
1.
50

Is isolated (floats) with respect to ground, or
RLC-SVD03A-EN

Module Power and Miscellaneous I/O
2. Has its negative terminal tied to chassis ground.
If the intended source does not meet the above requirement, an isolation
module must be used
The 4-20mA/2-10VDC inputs may be tested in the following ways:
1.

Enable External Chilled Water Setpoint and/or External Current Limit Setpoint in the Operator Settings Menu. Advance display to Active Chilled
Water Setpoint or Active Current Limit Setpoint to observe the respective
setpoint in the Chiller Report.

2. With all wiring in place, apply an external voltage or current to the External Chilled Water Setpoint inputs (TB1-4 & 5) or the External Current Limit
Setpoint (TB1-7 & 8). The voltage measured at the terminals and the
resulting setpoint, as read on the CLD, should agree with the Table 17 for
Chilled Water Setpoint inputs and Table 18 for Current Limit Setpoints
inputs. Be sure to wait long enough when reading the display as the values are slew rate limited.
3. Disconnect all wiring to these inputs. The setpoints should slew back to
the chiller's Front Panel settings.
4. Disconnect all wiring and install fixed resistors of values near those
shown in the following tables across TB1-3,5 or TBl-6,8. The resulting setpoints should agree with the table values.
Table 17

RLC-SVD03A-EN

Input Values vs. External Chilled Water Setpoint

INPUTS
Resist (ohms)

Current (ma)

Voltage (Vdc)

Resulting Chilled
Water Setpt (F)±4F

94433

4.0

2.0

0.0

68609

5.2

2.6

5.0

52946

6.5

3.2

10.0

42434

7.7

3.9

15.0

34889

8.9

4.5

20.0

29212

10.2

5.1

25.0

24785

11.4

5.7

30.0

21236

12.6

6.3

35.0

18327

13.8

6.9

40.0

15900

15.1

7.6

45.0

13844

16.3

8.2

50.0

12080

17.5

8.8

55.0

10549

18.8

9.4

60.0

Module Power and Miscellaneous I/O
Table 18

Input Values vs. External Current Limit Setpoint

Resist (ohms)

INPUTS
Current (ma)

Voltage (Vdc)

Resulting Current
Limit Setpt (%RLA)±5%

49000

4.0

2.0

29000

6.0

3.0

19000

8.0

4.0

13000

10.0

5.0

9000

12.0

6.0

6143

14.0

7.0

4010

16.0

8.0

100

2333

18.0

9.0

110

1000

20.0

10.0

120

Setpoint Priority
There are many ways in which the Chilled Water and Current Limit setpoints
can be adjusted or reset when the Options Module is present in the Chiller
control system. The following flow charts show how these methods are prioritized and arbitrated under normal operating conditions. When abnormal
conditions are present, such as loss of Tracer communications or out of range
values on external setpoint inputs, the system will default to other methods.

RLC-SVD03A-EN

Module Power and Miscellaneous I/O
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