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Sequence of Operation
COOLING (COOLING ONLY OR HEAT PUMP)
When the thermostat calls for cooling, 24 volts is put on
the blower time-delay relay coil and then the indoor blow-
er relay energizes. The normally open contacts close,
causing the indoor blower motor to operate. The circuit
between R and Y is completed, closing the circuit to the
contactor in the outdoor unit, starting the compressor and
outdoor fan motor.
On heat pumps, circuit R and O energizes the reversing
valve, switching the valve to the cooling position. (The re-
versing valve remains energized as long as the thermo-
stat selector switch is in the COOL position.)
At the completion of the cooling demand, the indoor blow-
er and outdoor unit should cycle o. Air handler should
cycle o 45 seconds after the outdoor unit shuts o.
HEATING (ELECTRIC HEAT ONLY)
When the thermostat calls for heat, the circuit between R
and W is completed, and the heat sequencer is energized.
A time delay follows before the heating elements and the
indoor blower motor come on. Units with a second heat
sequencer can be connected with the rst sequencer to W
on the thermostat subbase, or they may also be connect-
ed to a second stage on the subbase.
HEATING (HEAT PUMP)
When the thermostat calls for heating, 24 volts is put on
the blower time-delay relay coil. Then normally open con-
tacts close, causing the indoor blower motor to operate.
The circuit between R and Y is completed, closing the cir-
cuit to the contactor in the outdoor unit, starting the com-
pressor and outdoor fan motor.
If the room temperature should continue to fall, the cir-
cuit between R and W1 is completed by the second-stage
heat room thermostat. Circuit R-W1 energizes a heat se-
quencer. The completed circuit will energize supplemen-
tal electric heat (if applicable). Units with a second heat
sequencer can be connected with the rst sequencer to
W1 on the thermostat. They may also be connected to a
second heating stage W2 on the thermostat subbase.
EMERGENCY HEAT (HEATING HEAT PUMP)
If the selector switch on the thermostat is set to the emer-
gency heat position, the heat pump will be locked out of
the heating circuit, and all heating will be electric heat (if
applicable). A jumper should be placed between W2 and E
on the thermostat subbase so that the electric heat control
will transfer to the rst-stage heat on the thermostat. This
will allow the indoor blower to cycle on and o with the
electric heat when the fan switch is in the AUTO position.
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