Carrier 38AKS028-044 Installation, Start-up And Service Instructions Manual

Contents

Oil Pressure Safety Switch (OPS) — The OPS inthe control circuit stops the compressor and unit, if properoil pressure differential is not established at start-up or main-tained during operation. If OPS stops the unit, determine thecause and correct before restarting unit. Failure to do so willconstitute abuse. Equipment failure due to abuse may voidthe warranty.Compressor ProtectionCIRCUIT BREAKER — Calibrated trip manual reset, am-bient compensated, magnetic breaker protects against motoroverload and locked rotor conditions.CONTROL MODULE TIMER — This control protects com-pressor against short cycling. See Sequence of Operation onpage 17.CRANKCASE HEATER — This minimizes absorption ofliquid refrigerant by oil in crankcase during brief or ex-tended shutdown periods.IMPORTANT: Never open any switch or disconnectthat deenergizes the crankcase heater unless unit is be-ing serviced or is to be shut down for a prolonged pe-riod. After a prolonged shutdown on a service job, en-ergize the crankcase heater for 24 hours before startingthe compressor.High-Pressure Switch — This switch has fixed, non-adjustable settings. Switch is mounted on the compressor (SeeTable 4).Low-Pressure Switch — This switch has fixed, non-adjustable settings. Switch is mounted on the compressor.(See Table 4.)Table 4 — Pressure Switch Settings, psig (kPa)HIGH PRESSURE LOW PRESSURECutout Cut-in Cutout Cut-in426 ± 7(2937 ± 48)320 ± 20(2206 ± 138)27 ± 3(186 ± 21)44 ± 5(303 ± 34)Winter Start Control — Bypass relay timer bypasseslow-pressure switch for 2 minutes on unit start-up.Head Pressure Control — Control maintains ad-equate discharge pressure under low ambient temperature con-ditions. See Table 5.FAN CYCLING — These 38AKS units have standard pro-vision for fully automatic intermediate-season head pressurecontrol through condenser fan cycling. Fan no. 2 is cycledby a fan cycling pressure switch (FCPS) which responds tovariation in discharge pressure. The pressure sensor is lo-cated in the liquid line of the refrigerant circuit. Fan no. 3cycling is controlled by outdoor-air temperature through anair temperature switch (ATS) (38AKS044 units only).Table 5 — Minimum Outdoor-AirOperating TemperatureUNIT38AKSCOMPRCAP. (%)CONDTEMP,F (C)MIN OUTDOOR TEMP, F (C)StandardUnitLow AmbientControl(MotormasterT)028 100 90 (32) 31 (–1) –20 (–29)67 80 (27) 35 (2) –20 (–29)33 70 (21) 43 (6) –20 (–29)034 100 90 (32) 30 (–1) –20 (–29)67 80 (27) 34 (1) –20 (–29)33 70 (21) 42 (6) –20 (–29)044100 90 (32) 25 (–4) –20 (–29)67 80 (27) 30 (–1) –20 (–29)33 70 (21) 35 (2) –20 (–29)The ATS is located in the lower divider panel between thecompressor compartment and condenser section. Through ahole in the panel, the sensing element is exposed to air en-tering the no. 1 fan compartment. Fan no. 1 is noncycling.Table 6 shows the operating settings of the FCPS and theATS.Table 6 — Fan Cycling ControlsCONTROL BY SWITCH OPENS SWITCH CLOSESTemp, F (C) 70 ± 3 (21 ± 1.7) 80 ± 3 (27 ± 1.7)Pressure,psig (kPa) 160 ± 10 (1103 ± 69) 260 ± 15 (1793 ± 103)NOTE: See Fig. 6 and 7 for fan arrangement.20