Trane R Series Guide

August 2005 RLC-SVD03A-EN
© American Standard Inc. 2005
Model
RTAA 70-125 Ton
RTWA 70-125 Ton
RTUA 70-125 Ton
Diagnostic
Troubleshooting
Repair
Series R®
70-125 Ton Air-Cooled and Water-Cooled
Rotary Liquid Chillers

2RLC-SVD03A-EN
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.
NOTICE: Warnings and Cautions appear at appropriate sections through-
out 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 property-
damage only accidents.

RLC-SVD03A-EN 3
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

4RLC-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.
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 elimi-
nation. 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.
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

RLC-SVD03A-EN 5
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 communica-
tions 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 inter-
processor 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, segre-
gation is maintained.
In addition to the modules, there are a number of “system level” compo-
nents 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

6RLC-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 tempera-
tures 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 7
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 communica-
tions 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.

8RLC-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 coordi-
nated 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 infor-
mation 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 con-
trolled 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

RLC-SVD03A-EN 9
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
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.
Communication problems can result from any of the following:
1. 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 set-
ups 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 dia-
gram 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.

10 RLC-SVD03A-EN
Interprocessor Communication
Figure 1 IPC Link Order For 70-125 Ton RTAA
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