Carrier 30GTN Service And Troubleshooting Manual

Also see for 30GTN: Product data Installation instructions Installation instructions

Carrier 30GTN Service And Troubleshooting Manual Manual pdf 63 page image

Safety Devices — Chillers contain many safety de-vices and protection logic built into electronic control. Fol-lowing is a brief summary of major safeties.COMPRESSOR PROTECTIONCircuit Breaker — One manual-reset, calibrated-trip mag-netic circuit breaker for each compressor protects against over-current. Do not bypass or increase size of a breaker to cor-rect problems. Determine cause for trouble and correct beforeresetting breaker. Circuit breaker must-trip amps (MTA) arelisted on individual circuit breakers, and on unit labeldiagrams.30GTN,R070 (50 Hz), 080-110 and 230B-315B Compres-sor Protection Board (CPCS) — The CPCS is used to con-trol and protect compressors and crankcase heaters. Boardprovides following features:• compressor contactor control• crankcase heater control• ground current protection• status communication to processor board• high-pressure protectionOne large relay is located on CPCS board that controlscrankcase heater and compressor contactor. In addition, thisrelay provides a set of contacts that the microprocessor moni-tors to determine operating status of compressor. If the MBBdetermines that compressor is not operating properly throughsignal contacts, control locks compressor off.The CPCS contains logic that can detect if current-to-ground of any winding exceeds 2.5 amps; if so, compressorshuts down.A high-pressure switch with a trip pressure of426 ± 7 psig (2936 ± 48 kPa) is mounted on each compres-sor; switch setting is shown in Table 32. Switch is wired inseries with the CPCS. If switch opens, CPCS relay opens,processor detects it through signal contacts, and compressorlocks off. A loss-of-charge switch is also wired in series withthe high-pressure switch and CPCS.If any of these switches opens during operation, the com-pressor stops and the failure is detected by the MBB whensignal contacts open. If lead compressor in either circuit isshut down by high-pressure switch, ground current protec-tor, loss of charge switch, or oil pressure switch, all com-pressors in the circuit are locked off.30GTN,R130-210, 230A-315A AND 330A/B-420A/B — Acontrol relay in conjunction with a ground fault module re-places the function of the CPCS (above). To reset, press thepush-button switch near the Marquee display).Table 32 — Pressure Switch Settings,psig (kPa)SWITCH CUTOUT CUT-INHigh Pressure 426 ± 7(2936 ± 48) 320 ± 20(2205 ± 138)Loss-of-Charge 7 (48.2) 22 (151.6)LOW OIL PRESSURE PROTECTION — Lead compressorin each circuit is equipped with a switch to detect low oilpressure. Switch is connected directly to processor board.Switch is set to open at approximately 5 psig (35 kPa) andto close at 9 psig (62 kPa) maximum. If switch opens whencompressor is running, CR or processor board stops all com-pressors in circuit. During start-up, switch is bypassed for2 minutes.CRANKCASE HEATERS — Each compressor has a180-w crankcase heater to prevent absorption of liquid re-frigerant by oil in crankcase when compressor is not run-ning. Heater power source is auxiliary control power, inde-pendent of main unit power. This assures compressor protectioneven when main unit power disconnect switch is off.IMPORTANT: Never open any switch or disconnectthat deenergizes crankcase heaters unless unit is beingserviced or is to be shut down for a prolonged period.After a prolonged shutdown or service, energize crank-case heaters for 24 hours before starting unit.COOLER PROTECTIONFreeze Protection — Cooler can be wrapped with heater cablesas shown in Fig. 32, which are wired through an ambienttemperature switch set at 36 F (2 C). Entire cooler is cov-ered with closed-cell insulation applied over heater cables.Heaters plus insulation protect cooler against low ambienttemperature freeze-up to 0° F (−18 C).IMPORTANT: If unit is installed in an area where am-bient temperatures fall below 32 F (0° C), it is rec-ommended that inhibited ethylene glycol or other suit-able corrosion-inhibitive antifreeze solution be used inchilled-liquid circuit.Low Fluid Temperature — Main Base Board is programmedto shut chiller down if leaving fluid temperature drops below34 F (1.1 C) for water or more than 8° F (4.4° C) belowset point for brine units. The unit will shut down without apumpout. When fluid temperature rises to 6° F (3.3° C ) aboveleaving fluid set point, safety resets and chiller restarts. Re-set is automatic as long as this is the first occurrence.Loss of Fluid Flow Protection — Main Base Board containsinternal logic that protects cooler against loss of cooler flow.Entering and leaving fluid temperature sensors in cooler de-tect a no-flow condition. Leaving sensor is located inleaving fluid nozzle and entering sensor is located in firstcooler baffle space in close proximity to cooler tubes, as shownin Fig. 20. When there is no cooler flow and the compressorsstart, leaving fluid temperature does not change. However,entering fluid temperature drops rapidly as refrigerant enterscooler through EXV. Entering sensor detects this tempera-ture drop and when entering temperature is 3° F (1.6° C)below leaving temperature, unit stops and is locked off.Loss-of-Charge — A pressure switch connected to high sideof each refrigerant circuit protects against total loss-of-charge. Switch settings are listed in Table 32. If switch isopen, unit cannot start; if it opens during operation, unit locksout and cannot restart until switch is closed. Low charge isalso monitored by the processor when an EXV is used. Theloss-of-charge switch is wired in series with the high-pressure switch on each circuit’s lead compressor.LEGENDT — ThermistorFig. 32 — Cooler Heater Cables63