Cooling Cycle of Operation.

(4) The fan motor starts when the selector switch is placed in the VENTILATE position.

(5) In the COOL position, the fan motor is in operation and the compressor motor contactor is energized through the

contacts of the thermostatic switch. The energized contactor supplies power to the compressor through the normally closed

contacts of the circuit breaker and the compressor overload protector. After the fan motor and compressor have started, the

operation of the refrigerant unit is controlled by the thermostat. Sensing a rise in the air temperature above the set point, the

thermostat opens its contacts, deenergizing the liquid line solenoid valve. This positions the system for bypass service.

(6) The HI-LO fan speed switch controls the speed of the fan motor and the fans

b. Cooling Cycle of Operation.

(1) The fan motor and compressor run continuously, whether the thermostat is calling for cooling or not, when the unit is

set to operate on the cooling cycle of operation. This feature provides a constant electrical load thus preventing voltage fluctuations

within the system.

(2) Bypass cycle of operation. When the conditioned air temperature falls below the thermostat setting, the circuit which

controls the solenoid valves is energeized causing:

(a) The hot gas bypass line to flow discharge gases through the evaporator pressure regulator bypassing a major

part of the compressor refrigerant vapor directly back to the suction side of the compressor.

(b) To prevent frost from forming on the evaorator, a back pressure regulating valve is provided to prevent the

suction pressure from decreasing to a pressure of 58 psig which corresponds to a temperature of less than 32 degrees F.

c. Heating Operation, Placing the selector switch in the LO-HEAT position actuates half the evaporator heaters mounted

in the air conditioned air stream directly behind the evaorator coil. When the selector switch is placed in the HI-HEAT position, the

remaining heaters are energized, providing maximum heating capacity.

5-8. General Repair Procedures.

a. If the refrigerant system must be opened for repair or replacement of parts, first discharge the refrigerant from the system,

Refer to paragraph 5-9 for instructions.

b. After discharging the system, allow the tubing to warm to the ambient temperature before opening the system; this delay

will help prevent the formation of condensation on the inside wall of the tubing. Plug or cap all openings as a part is removed to

minimize the entry of dirt and moisture into the system.

c. Use a silver solder on all soldered connections. Silver solder with a 50 percent silver capacity and a melting point of

approximately 1300 degrees F is recommended. Continually pass dry nitrogen through the tubing or connections being soldered to

prevent formation of harmful copper oxides.

5-9. Servicing the Refrigerant System.

a. Testing Refrigerant System for Leaks.

Refer to paragraph 4-38, and test refrigerant system for leaks.

NOTE: In accordance with Environmental Protection Agency regulations, refrigerants cannot be discharged into the atmosphere.

A refrigerant recovery& recycling unit must be used whenever discharging the refrigerant system,

b. Releasing Refrigerant for Service.

NOTE: Operation of the recovery/recycling unit must be by AUTHORIZED PERSONNEL ONLY

Connect and operate a recovery/recycling unit in accordance with the manufacturer's instructions,

c. Evacuating the Refrigerant System.

(1) General. Opening the system to the atmosphere will c ause entry of air and moisture into the system. After any

servicing operation, when the system is opened, the entire system should be evacuated before recharging with refrigerant,

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