Carrier 48EJ, 48EW, 48EY024-068, 48AW, 48AY020-060, 48EK, 48AK, 48AJ specifications Protective Devices

Filter Drier — Replace whenever refrigerant system is ex- posed to atmosphere.

Protective Devices

COMPRESSOR PROTECTION

Overcurrent — Each compressor has one manual reset, cali- brated trip, magnetic circuit breaker. Do not bypass connec- tions or increase the size of the circuit breaker to correct trou- ble. Determine the cause and correct it before resetting the breaker.

Overtemperature — Each 06D type compressor (48AJ,AK, AW,AY020-035 and 48EJ,EK,EW,EY024-038 units only) has an internal protector to protect it against excessively high dis- charge gas temperatures.

Crankcase Heater — Each compressor has a crankcase heater to prevent absorption of liquid refrigerant by oil in the crank- case when the compressor is idle. Since power for the crank- case heaters is drawn from the unit incoming power, main unit power must be on for the heaters to be energized.

IMPORTANT: After a prolonged shutdown or service job, energize the crankcase heaters for 24 hours before starting the compressors.

EVAPORATOR FAN MOTOR PROTECTION — A manu- al reset, calibrated trip, magnetic circuit breaker protects against overcurrent. Do not bypass connections or increase the size of the breaker to correct trouble. Determine the cause and correct it before resetting the breaker. If the evaporator-fan motor is replaced with a different horsepower motor, resizing of the circuit breaker is required. Contact Carrier Application Engineering.

CONDENSER-FAN MOTOR PROTECTION — Each condenser-fan motor is internally protected against overtemperature.

HIGH- AND LOW-PRESSURE SWITCHES — If either switch trips, or if the compressor overtemperature switch activates, that refrigerant circuit will be automatically locked out. See Compressor Lockout Logic section on this page.

FREEZE PROTECTION THERMOSTAT (FPT) — Freeze protection thermostats are located on the evaporator coil for each circuit. One is located at the top and bottom of each coil. It detects frost build-up and turns off the compressor, allowing the coil to clear. Once the frost has melted, the compressor can be reenergized.

Relief Devices — All units have relief devices to protect against damage from excessive pressures (i.e., fire). These de- vices are installed on the suction line, liquid line, and on the compressor.

Power Circuit — A typical power wiring schematic is shown in Fig. 77.

Control Circuit, 24-V — This control circuit is protect- ed against overcurrent by a 3.2 amp circuit breaker (CB4). Breaker can be reset. If it trips, determine cause of trouble be- fore resetting. A typical 24-v control wiring schematic is shown in Fig. 78 and 79.

Control Circuit, 115-V — This control circuit is pro- tected against overcurrent by a 5.2 amp circuit breaker (CB3). Breaker can be reset. If it trips, determine cause of trouble be- fore resetting. A typical 115-v control wiring schematic is shown in Fig. 80 and 81.

Compressor Lockout Logic — If any of the safeties trip, the circuit will automatically reset (providing the safety has reset) and restart the compressor in 15 minutes. If any of the safeties trip 3 times within a 90-minute period, then the cir- cuit will be locked out and will require manual resetting by turning off either the unit disconnect or the control circuit breaker, or opening the thermostat.

If the compressors have bee off for more than 15 minutes and the outdoor-air temperature (OAT) is less than 45 F then safeties will be ignored for 5 minutes.

Replacement Parts — A complete list of replacement parts may be obtained from any Carrier distributor upon request.

LEGEND for Fig. 77-83 — Typical Wiring Schematics

			LEGEND
AFS	— Airflow Switch	HTSASP — Heating Supply Air Set Point
AHA	— Adjustable Heat Anticipator		Potentiometer
BP	— Building Pressure	HV	— High Voltage
BR	— Burner Relay	IDM	— Induced-Draft Motor
C	— Contactor, Compressor	IFC	— Indoor Fan Contactor
CAP	— Capacitor	IFCB	— Indoor Fan Circuit Breaker
CB	— Circuit Breaker	IFM	— Indoor-Fan Motor
CC	— Cooling Compensator	IFR	— Indoor-Fan Relay
CCB	— Controller Circuit Breaker	IGC	— Integrated Gas Unit Controller
CCH	— Crankcase Heater	IP	— Internal Protector
CLSASP — Cooling Supply Air		L	— Light
	Set Point Potentiometer	LPS	— Low-Pressure Switch
COM	— Communication	LS	— Limit Switch
COMP	— Compressor Motor	MGV	— Main Gas Valve
CR	— Control Relay	NC	— Normally Closed
CV	— Constant Volume	NO	— Normally Open
DM	— Damper Motor	OAT	— Outdoor-Air Thermostat
DP	— Duct Pressure	OD	— Outdoor
EC	— Enthalpy Control	OFC	— Outdoor-Fan Contactor
FLA	— Full Load Amps	OFM	— Outdoor-Fan Motor
FPT	— Freeze Protection Thermostat	PEC	— Power Exhaust Contactor
FU	— Fuse	PEM	— Power Exhaust Motor
GVR	— Gas Valve Relay	PES	— Power Exhaust Sequencer
HPS	— High-Pressure Switch	PESC	— Power Exhaust Sequencer Controller
HS	— Hall Effect Sensor	PL	— Plug Assembly

RAT	— Return-Air Thermistor
RS	— Rollout Switch
SAT	— Supply-Air Thermostat
SEN	— Sensor
SW	— Switch
TB	— Terminal Block
TC	— Thermostat, Cooling
TH	— Thermostat, Heating
TRAN — Transformer
UL	— Compressor Unloader
VFD	— Variable Frequency Drive

Terminal (Marked)

Terminal (Unmarked)

Terminal Block

Splice

Factory Wiring

Field Wiring

To indicate common potential only. Not to represent wiring.

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