Carrier 30GTN Service And Troubleshooting Manual

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Carrier 30GTN Service And Troubleshooting Manual Manual pdf 46 page image

TROUBLESHOOTINGCompressor Protection Control System (CPCS)Board — The compressor protection board controls thecompressor and compressor crankcase heater.The ground current protection is provided by the com-pressor board.The large relay located on the board is used to provide afeedback signal to the Main Base Board.The operation of the compressor board can be checkedusing the Service Test procedure. When the Service Test stepis turned on, the compressor board is energized. All safetiesare continuously monitored. The crankcase heater will be turnedoff and the compressor contactor will be turned on. The feed-back contacts will close and the Main Base Board (MBB)will read the feedback status.If the board does not perform properly, use standard wir-ing troubleshooting procedures to check the wiring for opencircuits. Refer to Alarms and Alerts section on page 45 foralarm or alert codes for possible causes for failure.If a compressor short-to-ground exists, the compressor boardmay detect the short before the circuit breaker trips. If thisis suspected, check the compressor for short-to-ground fail-ures with an ohmmeter. The ground current is sensed with acurrent toroid (coil) around all 3 or 6 wires between the mainterminal block and the compressor circuit breaker(s).Compressor Ground Current (CGC) Board(30GTN,R130-210, 230A-315A, and 330A/B-420A/B) — One board is used for each circuit of theseunits. Each board receives input from up to 4 toroids wiredin series, one toroid per compressor. With 24 v supplied atterminals A and B, a current imbalance (compressor groundcurrent) sensed by any toroid causes the NC (normally closed)contacts to open, shutting down the lead compressor in theaffected circuit. All other compressors in that circuit shut downas a result. The NC contacts remain open until the circuit isreset by momentarily deenergizing the board using the push-button switch.If the NC contacts open, it is necessary to remove toroidsfrom the T1-T2 circuit to determine which toroid is causingthe trip. The chiller circuit can then be put back on line afterthe circuit breaker of the faulty compressor is opened. Thecompressor problem can then be diagnosed by normal trouble-shooting procedures.EXV Troubleshooting — If it appears that the EXV isnot properly controlling operating suction pressure or super-heat, there are a number of checks that can be made usingthe quick test and initialization features built into theComfortLink™ control.Follow the procedure below to diagnose and correct EXVproblems.STEP 1 — CHECK PROCESSOR EXV OUTPUTS — CheckEXV output signals at the J6 and J7 terminals of the EXVboard.Turn unit power off. Connect the positive lead of the meterto terminal 3 on connector J6 on the EXV board. Set meterfor approximately 20 vdc. Turn unit power on. Enter andenable the Service Test mode. Locate the appropriate valveunder ‘OUTS.’ Select the desired percentage and press En-ter to move the valve. The valve will overdrive in both di-rections when either 0% or 100% are entered. During thistime, connect the negative test lead to terminals 1, 2, 4, and5 in succession. The voltage should fluctuate at each pin. Ifit remains constant at a voltage or at 0 v, replace the EXVboard. If the outputs are correct, then check the EXV.To test Circuit B outputs, follow the same procedure above,except connect the positive lead of the meter to terminal 3on connector J7 on the EXV board and the negative lead toterminals 1, 2, 4, and 5 in succession.STEP 2 — CHECK EXV WIRING — Check wiring to EXVsfrom J6 and J7 terminal strips on EXV board.1. Check color coding and wire connections. Make sure thatwires are connected to correct terminals at J6 and J7 ter-minal strips and EXV plug connections. Check for cor-rect wiring at driver board input and output terminals. SeeFig. 2-4.2. Check for continuity and tight connection at all pinterminals.3. Check plug connections at J6 and J7 terminal strips andat EXVs. Be sure EXV connections are not crossed.STEP 3 — CHECK RESISTANCE OF EXV MOTOR WIND-INGS — Remove plug at J6 and/or J7 terminal strip andcheck resistance between common lead (red wire, terminalD) and remaining leads A, B, C, and E. Resistance should be25 ohms ± 2 ohms.STEP 4 — CHECK THERMISTORS THAT CONTROL EXV— Check thermistors that control processor output voltagepulses to the EXVs. Circuit A thermistor is T7, and circuitB thermistor is T8. Refer to Fig. 9 and 10 for location.1. Use service test to determine if thermistors are shorted oropen.2. Refer to Thermistors section on page 57 for details onchecking thermistor calibration.50% CAPACITY AT 20 mA75% CAPACITY AT 12 mA100% CAPACITY AT 4 mA0 2 4 6 8 10 12 14 16 18 20DEMAND LIMIT SIGNAL – 4 - 20 mA INPUT (VOLTS DC)100806040200MAX. ALLOWABLE LOAD (%)Fig. 21 — 4 to 20 mA Demand Limiting46