HEATING. - TM-5-4120-369-140012

TM 5-4120-369-14

The compressor (1) takes cold, low pressure refrigerant gas and compresses it to a high

temperature, high pressure gas. This gas flows through the copper tubing to the split condenser

coil (3) and receiver (4).

The condenser fan draws outside ambient air over and through the two section condenser

coil (3).

The high temperature, high pressure gas from the compressor (1) is cooled by the flow

of air and is changed into a high pressure liquid.

The liquid sight glass (5) indicates the presence of moisture and quantity of refrig-

erant in the system.

The drier/filter dehydrator (6) removes any moisture (Water vapor) or dirt that may be

carried by the liquid refrigerant.

The solenoid valve (7) is controlled by the temperature selector on the control panel.

This valve will shut off the flow of refrigerant to the evaporator section when the temperature in

the conditioned area reaches the set point.

The expansion valve (8) senses the temperature and pressure of the refrigerant as it

leaves the evaporator coil. By use of the feeler bulb in the bulb well (11) and "external equalizer

line" the valve constantly adjusts the flow of liquid refrigerant to the evaporator coil (10).

As the high pressure liquid refrigerant leaves the expansion valve (8) it enters the

evaporator coil (10). As the liquid enters the coil, due to the size difference between the coil

and the tubing, the pressure is suddenly decreased. As the pressure decreases the liquid

refrigerant "flashes" to a gas. The evaporator blower circulates the warm air from the condition-

ed space over and through the evaporator coil. Liquid absorbs heat when it changes from a liquid

to a gas. As the air from the conditioned spaces comes in contact with evaporator coil (10), the

air is cooled.

The accumulator (12) holds any liquid refrigerant which did not change to a gas in the

evaporator. Heat in the evaporator section will boil this liquid to a gas before entering the com-

pressor.

To prevent compressor damage during start-up, solenoid valve (19) is normally open to

equalize pressure on both sides of the compressor.

b. Bypass System. This unit has a bypass system which allows cooling operation at low

cooling loads without cycling the compressor on and off. In bypass the refrigerant is from the

discharge to the suction side of the compressor, bypassing the evaporator coil (10).

When the temperature selector on the control panel senses that cooling conditions have

reached the set point, it closes the solenoid valve (7) to shut off refrigerant flow to the evapor-

ator coil (10).

As the compressor suction pressure starts to drop, the pressure regulators (20) open

to allow flow of hot gas from the compressor.

The quench valve (18) senses the temperature of the gas at the suction side of the

compressor. To prevent excessively hot gas from reaching the compressor the quench valve

(18) opens to allow liquid refrigerant to mix with the hot gas.

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HEATING.

a. When the MODE SELECTOR is set for HIGH Heat, six heating elements. located behind

the evaporator coil are energized. These elements are protected from overheating by a thermal

cutout switch . Three of the elements are controlled by the TEMPERATURE SELECTOR, and

remaining three are on all of the time. When set for LOW, only the three thermostatically con-

trolled elements are energized.

The two speed fan can be set for either HIGH or LOW operation during heating.

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