Specification

55
CONTROLS
Operating sequence
Heating (Single Phase Models) -- (See unit wiring label) On a call
for heating, terminal W of the thermostat is energized, starting the
induced-draft motor for a 5 second pre-purge. When the pressure
switch senses that the induced-draft motor is moving sufficient
combustion air, the burner sequence begins. This function is
controlled by the integrated gas unit controller (IGC). The indoor
(evaporator) –fan motor is energized 30 seconds after flame is
established. When the thermostat is satisfied and W is
de-energized, the burners stop firing and the indoor (evaporator)
fan motor shuts off after a 90 second time-off delay. Please note
that the IGC has the capability to automatically reduce the indoor
fan motor on delay and increase the indoor fan motor off delay in
the event of high duct static and/or a partially-clogged filter.
Heating (Three Phase Models) -- On a call for heating, terminal
W of the thermostat is ener gized, starting the induced--draft motor.
When the pressure switch senses that the induced-- draft motor is
moving sufficient combustion air, the burner sequence begins. This
function is performed by the integrated gas unit controller (IGC).
The indoor (evaporator)-- fan motor is energized 45 sec after flame
is established. When the thermostat is satisfied and W is
de-- energized, the burners stop firing and the indoor (evaporator)
fan motor shuts off after a 45--sec time--off delay. Please note that
the IGC has the capability to automatically reduce the indoor fan
motor on delay and increase the indoor fan motor off delay in the
event of high duct static and/or partially --clogged filter.
Cooling — When the system thermostat calls for cooling, 24 V is
supplied to the “Y” and “G” terminals of the thermostat. This
completes the circuit to the contactor coil (C) and indoor
(evaporator) fan relay (IFR). The normally open contacts of
energized C close and complete the circuit through compressor
motor (COMP) to outdoor (condenser) fan motor (OFM). Both
motors start instantly. The set of normally open contacts of
energized IFR close and complete the circuit through IFM. The
IFM starts instantly.
On the loss of the thermostat call for cooling, 24 V is removed
from both the “Y” and “G” terminals (provided the fan switch is in
the “AUTO” position) de-- energizing the compressor contactor and
opening the contacts supplying power to compressor/OFM. After a
60--second delay (1-- phase) or 90-- second delay (3--phase), the IFM
shuts off. If the thermostat fan selector switch is in the “ON”
position, the IFM will run continuously.
NOTE: On units with a Time Guard

II device: Once the
compressor has started and then stopped, it cannot be restarted
again until 5 minutes have elapsed.
PY4G -- -- B