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OPERATING SEQUENCE
Heating — On a call for heating, terminal “W” of the thermostat
is energized, starting the induced-draft motor. When the hall-
effect sensor on the induced-draft motor senses that it has
reached the required speed, the burner sequence begins. This
function is performed by the integrated gas control (IGC). The
evaporator fan motor is energized 45 seconds after flame is es-
tablished. When the thermostat is satisfied and “W” is de-
energized, the burners stop firing and the evaporator fan motor
shuts off after a 45-second time-off delay.
Cooling — When the room temperature rises to a point that is
slightly above the cooling control setting of the thermostat, the
thermostat completes the circuit between thermostat terminal R
to terminals Y and G. These completed circuits through the ther-
mostat connect contactor coil (C) (through unit wire Y) and blow-
er relay coil (BR) (through unit wire G) across the 24-v
secondary of transformer (TRAN).
The normally open contacts of energized contactor (C) close and
complete the circuit through compressor motor (COMP) to con-
denser (outdoor) fan motor (OFM). Both motors start instantly.
The set of normally open contacts of energized relay BR close
and complete the circuit through evaporator blower (indoor) fan
motor (IFM).
NOTE: Once the compressor has started and then has stopped,
it should not be started again until 5 minutes have elapsed.
The cooling cycle remains “on” until the room temperature drops
to a point that is slightly below the cooling control setting of the
room thermostat. At this point, the thermostat “breaks” the circuit
between thermostat terminal R to terminals Y and G. These
open circuits de-energize contactor coil C and relay coil BR. The
condenser and compressor motors stop. After a 30-second de-
lay, the blower motor stops. The unit is in a “standby” condition,
waiting for the next “call for cooling” from the room thermostat.
The ICM FIOP indoor blower operation with a call
for fan oper-
ation (G) in cooling mode will perform by the on/off delay profile
selected on the Easy Select™ circuit board.
CONTROLS