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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 RLC-SVD03A-EN
© American Standard Inc. 2005
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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 ac
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Contents General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Service Philosophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 System Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 System Level Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Interprocessor Communications . . . . . . . . . . .
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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 Controller Name Abbrev. Designation Chiller Module CPM 1U2 Optio
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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
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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 inte
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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 wir
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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 sche
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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 WA
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Interprocessor Communication Figure 1 IPC Link Order For 70-125 Ton RTAA 10 RLC-SVD03A-EN
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Interprocessor Communication . Table 2 IPC Address Dip Switch (SW1) Settings for MCSP an EXV Modules MODULE DESIG. CONTROLLING DIP SWITCH SETTING SW1-1 SW1-2 MCSP “A” 1U4 COMPRESSOR A OFF OFF MCSP “B” 1U5 COMPRESSOR B OFF ON EXV 1U3 CKTS. 1 & 2 OFF OFF 3. Loss of power to a module: Generally a power loss to a particular module will only affect communica- tions with that module. The module can usually be identified by analysis of the IPC diagnostics. (When the display is blank, check power at th
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Interprocessor Communication 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 commu- nications and thus fail
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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
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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 14 RLC-SVD03A-EN
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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 wit
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Temperature Sensor Checkout 4. Again measure the temperature at the sensor with an accurate thermom- eter; 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.
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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 Actual Thermistor Actual Actual Thermistor Actual Actual Thermistor Temp. Resistance Voltage Temp. Resistance Voltage Temp. Resistance Voltage (F) (Ohms) (Volts DC) (F) (Ohms) (Volts DC) (F) (Ohms) (Volts DC) -20.0 170040.3 4.448 30.0 34838.9 3.120 80.0 9297.5
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Temperature Sensor Checkout Table 4 Sensor Conversion Data: Saturated Condenser and Entering Oil Temperature Matched Pairs (6RT12, 3B1RT1; 6RT13, 4B1RT2) Actual Actual Thermistor Actual Actual Thermistor Actual Actual Thermistor Temp. Resistance Voltage Temp. Resistance Voltage Temp. Resistance Voltage (F) (Ohms) (Volts DC) (F) (Ohms) (Volts DC) (F) (Ohms) (Volts DC) 0.0 87510.3 4.651 50.0 19955.0 3.765 100.0 5824.3 2.356 1.0 84745.9 4.641 51.0 19427.9 3.740 101.0 5694.2 2.327 2.0 82072.1 4.630
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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 i
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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-ener- gized. Timing is determined by the time required to position the EXV 3. After the EXV is positioned: � t
