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Sequence of Operation
Cooling (Cooling Only or Heat Pump)
On all models, the 24 volt line will go directly to the termi-
nal board from the transformer. The normally open con-
tacts close, causing the indoor blower motor to operate;
depending on the indoor blower motor, there may be a
delay. 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 off. Air handler should
cycle off 45 seconds after the outdoor unit shuts off.
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 first sequencer to W
on the thermostat sub-base, or they may also be connect-
ed to a second stage on the sub-base.
Heating (Heat Pump)
On all models, the 24 volt line will go directly to the termi-
nal board from the transformer. The normally open con-
tacts close, causing the indoor blower motor to operate;
depending on the indoor blower motor, there may be a
delay. 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.
If the room temperature continues to decrease, 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 first sequencer to
W1 on the thermostat. They may also be connected to
a second heating stage W2 on the thermostat sub-base.
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 sub-base so that the electric heat con-
trol will transfer to the first-stage heat on the thermostat.
This will allow the indoor blower to cycle on and off with
the electric heat when the fan switch is in the AUTO po-
sition.
Constant Torque Speed Blower Motor
(ECM) (B3)
To Remove Blower From Unit: Remove wiring jack plug and
three screws and slide blower out.
The constant torque ECM (electronically commutated mo-
tor) communicates with the air handler control via 24VAC
inputs. It is programmed to provide a constant level of
torque (current / power) to the motor. This is a multi-tap
motor with the ability to have 1 to 5 programmed levels of
torque (see table 4). Each value equals a specific amount
of torque to create the proper amount of airflow for each
system demand. This value is specific to model and size
of system.
Each tap can have a unique amount of torque programmed
for a specific purpose. For example, switching from Tap 1
to Tap 2 may increase the airflow, but not necessarily at
a specific interval like changing from low to medium low
speed on a PSC motor.
Internal components are shown in figure 23. The stator
windings are split into three poles which are electrically
connected to the controller. This arrangement allows mo-
tor windings to turn on and off in sequence by the control-
ler.
BLOWER MOTOR COMPONENTS
CONTROLLER
Page 26
TYPICAL BLOWER MOTOR
(B3) REMOVAL
Blower Motor (B3)
FIGURE 22
STATOR
(WINDINGS)
BEARING
ROTOR
FIGURE 23
OUTPUT
SHAFT
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