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SYSTEM OPERATION
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 atmospheric
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.
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 re-
moved 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 add-
ing more heat, and discharges hot, high pressure superheated
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.
COOLING CYCLE
COOLING ONLY MODELS
When the contacts of the room thermostat close, making
terminals R to Y and R to G, the low voltage circuit to the
contactor is completed starting the compressor and outdoor
fan motor. This also energizes the indoor blower through the
24V signal from the thermostat.
When the thermostat is satisfied, breaking the circuit be-
tween R to Y and R to G, the compressor and outdoor fan
motor will stop. The indoor blower will stop after the fan off
delay.
If the room thermostat fan selector switch should be set to
the "on" position then the indoor blower would run continu-
ous rather than cycling with the compressor.
HEAT PUMP MODELS
Any time the room thermostat is switched to cool, the O
terminal is energized. This energizes the 24 volt coil on the
reversing valve and switches it to the cooling position.
18
*PC15/*PH16**H41*
When the contacts of the room thermostat close, this closes
the circuit from R to Y and R to G in the unit.
This energizes the compressor contactor and will energize
the indoor blower instantly on models equipped with EEM
blower motor.
When the thermostat is satisfied, it opens its contacts break-
ing the low voltage circuit causing the compressor contactor
to open and indoor fan to stop after the programmed 60 sec-
ond off delay on models equipped with EEM blower motors.
If the room thermostat fan selector switch should be set to
the "on" position then the indoor blower would run continu-
ous rather than cycling with the compressor.
HEATING CYCLE
COOLING ONLY UNITS
NOTE: The following only applies if the cooling only unit has
an approved electric heat kit installed for heating. If auxiliary
electric heaters should be used, they may be controlled by
outdoor thermostats (OT18-60A or OT/EHR18-60A).
*PC MODELS EQUIPPED WITH EEM BLOWER MO-
TORS
With the thermostat set to the heat position and a call for
heat, R to W will be energized. This will energize the electric
heat sequencers and the EEM motor. The electric heat will
be energized through the normally open contacts of the elec-
tric heat sequencers. The indoor blower will be energized
through W from the thermostat.
When the thermostat is satisfied, this breaks the circuit from
R to W. This will turn off the electric heaters, and the indoor
blower after the programmed 60 second off delay.
HEAT PUMP UNITS
On a call for first stage heat, the contacts of the room ther-
mostat close. This energizes terminals R to Y and R to G,
the low voltage circuit to the contactor is completed starting
the compressor and outdoor fan motor. This also energizes
the indoor blower instantly on models equipped with EEM
blower motors.
When the thermostat is satisfied, breaking the circuit be-
tween R to Y and R to G, the compressor and outdoor fan
motor will stop after the programmed 60 second off delay on
models equipped with EEM blower motors .
When auxiliary electric heaters are used, a two stage heat-
ing single stage cooling thermostat would be installed.
Should the second stage heating contacts in the room ther-
mostat close, which would be wired to W1 at the unit low
voltage connections, this would energize the coil(s) of the
electric heat relay(s). Contacts within the relay(s) will close,
bringing on the electric resistance heaters.
If auxiliary electric heaters should be used, they may be con-
trolled by outdoor thermostats (OT18-60A or OT/EHR18-60A).
EMERGENCY HEAT MODE (HEAT PUMPS)
NOTE: The following only applies if the unit has an approved
electric heat kit installed for auxiliary heating.
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