Carrier Complete Guide to Air Conditioner Models 38AKS028 and 38AKS044

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Oil Pressure Safety Switch (OPS) Ð The OPS in the control circuit stops the compressor and unit, if proper oil pressure differential is not established at start-up or main- tained during operation. If OPS stops the unit, determine the cause and correct before restarting unit. Failure to do so will constitute abuse. Equipment failure due to abuse may void the warranty.

Compressor Protection

CIRCUIT BREAKER Ð Calibrated trip manual reset, am- bient compensated, magnetic breaker protects against motor overload and locked rotor conditions.

CONTROL MODULE TIMER Ð This control protects com- pressor against short cycling. See Sequence of Operation on page 17.

CRANKCASE HEATER Ð This minimizes absorption of liquid refrigerant by oil in crankcase during brief or ex- tended shutdown periods.

IMPORTANT: Never open any switch or disconnect that 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 starting the compressor.

High-Pressure Switch Ð This switch has ®xed, non- adjustable settings. Switch is mounted on the compressor (See Table 4).

Low-Pressure Switch Ð This switch has ®xed, non- adjustable settings. Switch is mounted on the compressor. (See Table 4.)

Table 4 Ð Pressure Switch Settings, psig (kPa)

 

HIGH PRESSURE

LOW PRESSURE

 

Cutout

Cut-in

Cutout

Cut-in

426

± 7

320

± 20

27

± 3

44

±

5

(2937

± 48)

(2206

± 138)

(186

± 21)

(303

±

34)

Winter Start Control Ð Bypass relay timer bypasses low-pressure switch for 2 minutes on unit start-up.

Head Pressure Control Ð Control maintains ad- equate discharge pressure under low ambient temperature con- ditions. See Table 5.

FAN CYCLING Ð These 38AKS units have standard pro- vision for fully automatic intermediate-season head pressure control through condenser fan cycling. Fan no. 2 is cycled by a fan cycling pressure switch (FCPS) which responds to variation in discharge pressure. The pressure sensor is lo- cated in the liquid line of the refrigerant circuit. Fan no. 3 cycling is controlled by outdoor-air temperature through an air temperature switch (ATS) (38AKS044 units only).

Table 5 Ð Minimum Outdoor-Air

Operating Temperature

 

 

COND

MIN OUTDOOR TEMP, F (C)

UNIT

COMPR

TEMP,

Standard

Low Ambient

38AKS

CAP. (%)

Control

F (C)

Unit

 

 

(Motormaster )

 

 

 

 

 

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)

044

100

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 the compressor compartment and condenser section. Through a hole 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 the ATS.

Table 6 Ð Fan Cycling Controls

CONTROL BY

SWITCH OPENS

SWITCH CLOSES

Temp, F (C)

70 ± 3 (21 ± 1.7)

80 ± 3 (27 ±

1.7)

Pressure,

160 ± 10 (1103 ± 69)

260 ± 15 (1793

± 103)

psig (kPa)

 

 

 

NOTE: See Fig. 6 and 7 for fan arrangement.

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Contents Before Installation ContentsSafety Considerations Ð Physical Data Ð English Ð Physical Data Ð SIInstallation 38AKS UnitsCompressor Mounting Unit Length of Interconnecting PIPING, FT M Ð Refrigerant Piping Sizes Ð 60 HzÐ Refrigerant Piping Sizes Ð 50 Hz 38AKSElectrical Data 50-75 Length Insulated Wire Size AWGMm2 38AKS028 38AKS028C38AKS034 38AKS034C38AKS044 2437 38AKS044C 2745 1246AFS EquipGND LLS1BPR LlsvTime Delay Relay TDRTran TransformerSTART-UP Initial Check38AKS028 Charging Chart, 50/60 Hz 38AKS034 Charging Chart, 50/60 Hz 38AKS044 Charging Chart, 50/60 Hz Complete Unit Stoppage ServiceAccess for Servicing See Fig 38AKS Unit with Access Panels Removed Compressor Amount 06E926506E9275 06E9299Fan Cycling Controls Pressure Switch Settings, psig kPaMinimum Outdoor-Air Operating Temperature Troubleshooting Compressor Stops on LOW-PRESSURE ControlPackaged Service Training Remove and store in job le Preliminary InformationPre-Start-Up Start-Up OIL Level AT 1¤ 8 to 1¤ 3 FULL?