SYSTEM OPERATION
21
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 cycle is accomplished by using a unique tubular
design heat exchanger which provides efficient gas heating
on either natural gas or propane gas fuels. The heat
exchangers compact tubular construction provides excellent
heat transfer for maximum operating efficiency.
Inshot type gas burners with integral cross lighters are used
eliminating the need for adjustable air shutters. The same
burner is designed for use on either natural or propane gas
fuels.
The induced draft blower draws fuel and combustion air into
the burners and heat exchanger for proper combustion. A
pressure switch is used in conjunction with the I. D. blower
to detect a blocked flue condition.
Blower operation is controlled by the ignition control module.
The module allows for field adjustment of the blower delay at
the end of the heating cycle. The range of adjustment is for
90, 120, 150 or 180 seconds. The factory delay setting is 30
seconds delay on 150 seconds delay off.
Direct Spark Ignition (DSI) Systems
APG/GPG units are equipped with a direct spark ignition
system. Ignition is provided by 22,000 volt electronic spark.
A flame sensor then monitors for the presence of flame and
closes the gas valve if flame is lost.
