Manual 2100-578E
Page
27 of 41
SEqUENCE OF OPERATION
CoolING PART loAd
– Circuit R-Y1 makes at
thermostat pulling in compressor contactor, starting the
compressor and outdoor motor. The G (indoor motor)
circuit is automatically completed on any call for
cooling operation or can be energized by manual fan
switch on subbase for constant air circulation.
CoolING Full loAd
– Circuit R-Y1 & Y2
makes at the thermostat energizing the 2nd stage
solenoid in the compressor. The default position of
the compressor staging solenoid is non-energized. The
compressor will run at low capacity until this solenoid
is energized.
HEATING STAGE 1
– A 24V solenoid coil on
reversing valve controls heating cycle operation. Two
thermostat options, one allowing “Auto” changeover
from cycle to cycle and the other constantly energizing
solenoid coil during heating season and thus
eliminating pressure equalization noise except during
defrost, are to be used. On “Auto” option a circuit is
completed from R-B and R-Y1 on each heating “on”
cycle, energizing reversing valve solenoid and pulling
in compressor contactor starting compressor and
outdoor motor. R-G also make starting indoor blower
motor. Heat pump heating cycle now in operation.
The second option has no “Auto” changeover position,
but instead energizes the reversing valve solenoid
constantly whenever the system switch on subbase
is placed in “Heat” position, the “B” terminal being
constantly energized from R. A thermostat demand
for Stage 1 heat completes R-Y1 circuit, pulling in
compressor contactor starting compressor and outdoor
motor. R-G also make starting indoor blower motor.
HEATING STAGE 2
– Circuit R-Y1 & Y2 makes at
the thermostat energizing the 2nd stage solenoid in the
compressor.
PRESSURE SERVICE PORTS
High and low pressure service ports are installed on
all units so that the system operating pressures can be
observed. Pressure tables can be found later in the
manual covering all models. It is imperative to match
the correct pressure table to the unit by model number.
Upper and lower service doors must be attached to
obtain proper reading.
