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SEQUENCE OF OPERATION — STD NON-ICM UNITS
Cooling
NOTE: With the FAN switch in the ON position, 24 v is
supplied to the IFR through the G terminal on the thermo-
stat. This voltage energizes the coil of the contactor, closing
the normally-open set of contacts which provide continuous
power to the indoor (evaporator) fan motor (IFM). Moving
the FAN switch back to the AUTO. position, providing there
is not a call for cooling, deenergizes the IFR, opens the IFR
contacts, and deenergizes the IFM. The FAN switch in AUTO.
position cycles upon a call for cooling.
On a call for cooling, 24 v is supplied to the compressor
contactor (C) and IFR simultaneously through the Y and G
terminals of the thermostat, respectively. On units with a
compressor time delay relay, there is a built-in, 5-minute
(± 45 seconds) delay between compressor starts. Energizing
the contactor closes the normally-open set of contacts sup-
plying power to both the compressor and outdoor (con-
denser) fan motor (OFM). Energizing the IFR closes the
normally-open set of contacts providing power to the IFM.
On the loss of the call for cooling, 24 v is removed from
both the Y and G terminals of the thermostat (providing the
FAN switch is in the AUTO. position), deenergizing both
the contactor and IFR and opening both the contacts sup-
plying power to compressor/OFM and IFM.
Heating — If accessory electric heaters are installed, on a
call for heat, circuit R-W is made through the thermostat con-
tacts. Circuit R-G is made which energizes the IFR. If the
heaters are staged, then the thermostat closes a second set of
contacts W2 when second stage is required. When thermo-
stat is satisfied, contacts open, deenergizing the heater relay
and the IFR.
SEQUENCE OF OPERATION — ICM UNITS
Evaporator Fan — With the fan switch in the ON position,
24 v is supplied to the ICM motor through the ‘‘G’’ terminal
on the thermostat. This voltage provides continuous power
to the indoor (evaporator) fan motor (IFM). If the fan switch
is moved back to the AUTO position and there is not a call
for heating or cooling, 24 v is removed from the ‘‘G’’ ter-
minal and the evaporator fan remains energized for the de-
lay timing. When the fan switch is in AUTO, the fan cycles
with either the call for heating or cooling.
Cooling — On a call for cooling, 24 v is supplied to the com-
pressor contactor (C) and IFM simultaneously through the
‘‘Y’’ and ‘‘G’’ terminals of the thermostat. Energizing the
contactor closes the normally open set of contacts supplying
power to both the compressor and outdoor (condenser) fan
motor (OFM). On the loss of the call for cooling, 24 v is
removed from the ‘‘Y’’and ‘‘G’’terminals of the thermostat,
deenergizing the compressor and OFM. The evaporator fan
remains energized for the delay timing.
NOTE: Once the compressor has started and then stopped,
it cannot be restarted again until 5 minutes have elapsed.
Heating — If accessory electric heaters are installed, on a
call for heat, circuits R-W and R-G are made through the
thermostat contacts, energizing the heater relay and IFM. If
the heaters are staged, then the thermostat closes the second
set of contacts, W2, when the second stage is required. When
the thermostat is satisfied, contacts open, deenergizing the
heater relay and the IFM.
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