Amana R-410A Service Manual download pdf (Page 19)

SYSTEM OPERATION

COOLING

The refrigerant used in the system is R-410A. It is a clear,

colorless, non-toxic and non-irritating liquid. R-410A is a

50:50 blend of R-32 and R-125. The boiling point at atmo-

spheric pressure is -62.9°F.

A few of the important principles that make the refrigeration

cycle possible are: heat always flows from a warmer to a

cooler body. Under lower pressure, a refrigerant will absorb

heat and vaporize at a low temperature. The vapors may be

drawn off and condensed at a higher pressure and tempera-

ture to be used again.

The indoor evaporator coil functions to cool and dehumidify

the air conditioned spaces through the evaporative process

taking place within the coil tubes.

NOTE: The pressures and temperatures shown in the

refrigerant cycle illustrations on the following pages are for

demonstration purposes only. Actual temperatures and pres-

sures are to be obtained from the "Expanded Performance

Chart".

Liquid refrigerant at condensing pressure and temperatures,

(270 psig and 122°F), leaves the outdoor condensing coil

through the drier and is metered into the indoor coil through

the metering device. As the cool, low pressure, saturated

refrigerant enters the tubes of the indoor coil, a portion of the

liquid immediately vaporizes. It continues to soak up heat and

vaporizes as it proceeds through the coil, cooling the indoor

coil down to about 48°F.

Heat is continually being transferred to the cool fins and tubes

of the indoor evaporator coil by the warm system air. This

warming process causes the refrigerant to boil. The heat

removed from the air is carried off by the vapor.

As the vapor passes through the last tubes of the coil, it

becomes superheated. That is, it absorbs more heat than is

necessary to vaporize it. This is assurance that only dry gas

will reach the compressor. Liquid reaching the compressor

can weaken or break compressor valves.

The compressor increases the pressure of the gas, thus

adding more heat, and discharges hot, high pressure super-

heated gas into the outdoor condenser coil.

In the condenser coil, the hot refrigerant gas, being warmer

than the outdoor air, first loses its superheat by heat trans-

ferred from the gas through the tubes and fins of the coil. The

refrigerant now becomes saturated, part liquid, part vapor and

then continues to give up heat until it condenses to a liquid

alone. Once the vapor is fully liquefied, it continues to give up

heat which subcools the liquid, and it is ready to repeat the

cycle.

HEATING

The heating portion of the refrigeration cycle is similar to the

cooling cycle. By energizing the reversing valve solenoid coil,

the flow of the refrigerant is reversed. The indoor coil now

becomes the condenser coil, and the outdoor coil becomes

the evaporator coil.

The check valve at the indoor coil will open by the flow of

refrigerant letting the now condensed liquid refrigerant by-

pass the indoor expansion device. The check valve at the

outdoor coil will be forced closed by the refrigerant flow,

thereby utilizing the outdoor expansion device.

The restrictor orifice used with the CA*F, CHPF and CH**FCB

coils will be forced onto a seat when running in the cooling

cycle, only allowing liquid refrigerant to pass through the

orifice opening. In the heating cycle, it will be forced off the

seat allowing liquid to flow around the restrictor. A check valve

is not required in this circuit.

COOLING CYCLE

When the contacts of the room thermostat close making

terminals R to Y & G, the low voltage circuit of the transformer

is completed. Current now flows through the magnetic hold-

ing coils of the compressor contactor (CC) and fan relay

(RFC).

This draws in the normally open contact CC, starting the

compressor and condenser fan motors. At the same time,

contacts RFC close, starting the indoor fan motor.

When the thermostat is satisfied, it opens its contacts,

breaking the low voltage circuit, causing the compressor

contactor and indoor fan relay to open, shutting down the

system.

If the room thermostat fan selector switch should be set on

the "on" position, then the indoor blower would run continuous

rather than cycling with the compressor.

ASZ and SSZ models energize the reversing valve thorough

the "O" circuit in the room thermostat. Therefore, the revers-

ing valve remains energized as long as the thermostat

subbase is in the cooling position. The only exception to this

is during defrost.

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Amana R-410A Service Manual Page 19

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