SYSTEM OPERATION
8
Single-Stage Heat Pump Units
On a call for first stage heat, the contacts of the room
thermostat 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 on models equipped with the
EEM motor.
When the thermostat is satisfied, breaking the circuit
between R to Y and R to G, the compressor and outdoor
fan motor will stop. The indoor blower will stop after the
programmed 60 second off delay on models equipped with
the EEM motor.
Two-Stage Heat Pump Units
On a call for first stage heat, the contacts of the room
thermostat close. This energizes terminals R to Y1 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 motor.
When the thermostat is satisfied, breaking the circuit
between R to Y1 and R to G, the compressor and outdoor
fan motor will stop. The indoor blower will stop after the
programmed off delay.
During first stage operation the stat calls for second stage
heat. This energizes terminals R to Y2. This powers voltage
to the compressor solenoid allowing the compressor to
shift to full capacity. When the thermostat is satisfied,
breaking the circuit between R to Y1, R to Y2 and R to G,
the compressor and outdoor fan motor will stop. The indoor
blower will stop after the programmed off delay on the
motor.
When auxiliary electric heaters are used the Aux stage
heating contacts in the room thermostat close, which
would be wired to W1 at the unit low voltage connections,
this would energize the coil(s) of the electric heat
contactor(s)/sequencer(s). Contacts within the contactor(s)/
Sequencer(s) will close, bringing on the electric resistance
heaters. If auxilary electric heaters should be used, the
may be controlled 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.
A/GPH EEM Equipped Models Only:
With the thermostat set to the emergency heat position and
a call for 2nd stage heat, R to W1 will be energized. This
will energize the electric heat contactor(s)/sequencer(s)
and the EEM motor. The electric heat will be energized
through the normally open contacts of the electric heat
contactor(s)/sequencer(s). The indoor blower will be
energized through W from the thermostat.
DEFROST CYCLE
Package Heat Pumps
The defrosting of the outdoor coil is jointly controlled by the
defrost control board and the defrost thermostat.
Solid State Defrost Control
During operation the power to the circuit board is controlled
by a temperature sensor, which is clamped to a feeder tube
entering the outdoor coil. Defrost timing periods of 30, 60,
or 90 minutes may be selected by setting the circuit board
jumper to 30, 60, or 90 respectively. Accumulation of time
for the timing period selected starts when the sensor closes
(approximately 30° F), and when the room thermostat
calls for heat. At the end of the timing period, the unit’s
defrost cycle will be initiated provided the sensor remains
closed. When the sensor opens (approximately 60° F), the
defrost cycle is terminated and the timing period is reset.
If the defrost cycle is not terminated due to the sensor
temperature, a twelve minute override interrupts the unit’s
defrost period.
FAN OPERATION
Continuous Fan Mode
A/GPC & A/GPH EEM Equipped Models Only:
If the thermostat calls for continuous fan, the indoor blower
will be energized from the G terminal of the thermostat to
the EEM blower motor.
If a call for heat or cool occurs during a continuous fan call,
the EEM motor will always recognize the call for the highest
speed and ignore the lower speed call.
If the thermostat is not calling for heat or cool, and the
fan switch on the thermostat is returned to the automatic
position, the fan will stop after the programmed 60 second
off delay on units with the EEM motor.
