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: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
30
Sequence of Operation
FAN OPERATION
The FAN switch on the thermostat controls indoor fan operation. When
the FAN switch is placed in the ON position, the indoor (evaporator) fan
motor (IFM) is energized through the G terminal on the thermostat. The
motor’s internal logic then provides power to the indoor (evaporator) fan
motor (IFM). The IFM will run continuously when the FAN switch is set
to ON.
When the FAN switch is set to AUTO, the thermostat deenergizes the
IFM (provided there is not a call for cooling). The contacts open and the
IFM is deenergized. The IFM will be energized only when there is a call
for cooling, in heat pump heating mode or if the unit is equipped with
accessory electric heat, the indoor-fan motor will also run while the
accessory electric heat is energized.
NOTE:
Motors on this product are programmed for 60 second time
delay on tap 1 and 30 second time delay on tap 2. There is no time delay
on tap 3. The indoor fan will remain ON for the set time delay after G or
W2 is de-energized.
COOLING OPERATION
With a call for cooling (Y), the compressor, outdoor fan, and indoor fan
start immediately. When the cooling demand is met, Y de-energizes,
shutting the compressor, indoor fan and the outdoor fan.
HEATING OPERATION
With a call for heating (Y), the compressor, outdoor fan, and indoor fan
start immediately. If Y cannot satisfy the heating demand, the auxiliary
or backup heat (W2) energizes. In case of staged heating, W3 is
energized if the demand is not met. When heating demand is met, W3,
W2 and Y sequentially de-energize shutting the compressor, indoor fan
and the outdoor fan.
CONTINUOUS FAN
With the continuous indoor fan option selected on the thermostat, G is
continuously energized. The continuous fan speed will be the same as
the cooling fan speed.
DEFROST
Defrost board (DB) is a time and temperature control, which includes a
field-selectable time period between checks for defrost (30, 60, 90 and
120 minutes). The time period is factory-set at 60 minutes and should
only be adjusted by a trained service person. Electronic timer and defrost
cycle start only when contactor is energized and defrost thermostat
(DFT) is closed.
Defrost mode is identical to Cooling mode. The outdoor fan motor stops
because of “OF1” and “OF2” contacts opening on the defrost board, a
bank of optional electric heat turns on to warm air supplying the
conditioned space.
ELECTRIC RESISTANCE HEATING
If accessory electric heaters are installed, on a call for “Emergency Heat”
the thermostat energizes W which energizes the heater relay and in turn
energizes the electric heaters. The IFM is energized which starts the
indoor-fan motor. If the heaters are staged, W2 is energized when the
second stage of heating is required. When the need for heating is
satisfied, the heater and IFM are de-energized.
ECM Fan Motor Troubleshooting
Caution – Do not disconnect motor plugs under load.
• Check the high-voltage supply to motor. The ECM fan motor will
always have high voltage to the motor even when the motor is off.
The 24 volt signal cycles the motor on and off. The motor can accept
more than one 24 volt control signal to the different motor taps
without damaging it. The motor will default to the highest speed tap
that see a 24 volt signal.
Fan won’t run...
• Cycle power off to the unit. Disconnect the two plugs going into the
motor. One plug is the high voltage supply and the other is the low
voltage control.
• Cycle power back on and measure the high voltage supply plug to
determine if there is voltage at plug. If there is no voltage at plug,
determine if there is power to the unit. The easiest place to measure
the voltage is on the line side of the contactor. If there is voltage at the
contactor and no voltage at the plug, cycle the power back off and
inspect the wiring harness and plug for loose or broken connections.
• Replace the wiring harness and plug, if it is found to be defective.
• If there is power at the high voltage plug, check the low voltage
control signal.
• With the power on to the unit, verify that there is 24volts between R
and C in the low voltage control box. If there is not 24 volts at R and C
check the inline 3 amp fuse. If the fuse is blown, check for shorted,
bare or chaffed wires before installing another fuse in the holder. If
the fuse is good make sure there is line voltage on the primary side of
the transformer. Then check the secondary side of the transformer. If
there is line voltage on the transformer primary and no voltage on the
secondary; replace the transformer.
• If there is 24volts between R and C, jump R and G together in the low
voltage control box. Check to see if there is a 24 volt signal at pins 1,
2 or 3 referenced to common (ground) at the motor’s low voltage plug.
If there is no voltage between common and one of the pins, trace the
wires back to the low voltage control box.
• If there is power at the high voltage plug, voltage at pins 1, 2 or 3 on
the low voltage plug, the connections are good between the plugs and
motor and the motor is not running: replace the motor.
Two 24 volt signal wires will be connected from the thermostat to the
low voltage control plug. One wire (signal) will be for constant fan
(cooling) speed and the other will be for electric heat.
If there is an intermittent motor operation issue, check the 1000 ohm
resistor between the green “G” wire and the brown “C” wire in the unit’s
wiring harness. (See unit’s wiring diagram.) The resistor could be blown
(open). This resistor is in line with the fan motor to provide a load for the
thermostat’s triacs, or relay.
Time Delays
The unit/system time delays include:
• The air conditioning or heat pump units do not have any built in time
delays to start the cooling or heating cycle. Most residential
thermostats have an electronic safety start feature built into the
software to prevent compressor short cycling.
• The indoor fan motor (ECM) has a built in fan off delays on the first
two taps of the motor. The third motor tap will shut off immediately
after the 24v signal is gone. See the following for details:
Tap 1 - 60 second off delay
Tap 2 - 30 second off delay
Tap 3 - 0 second off delay
• The only other timing feature in the heat pump units are built into the
defrost board. See defrost board sequence for more details on defrost
time delays and setups.
Pressure Switches
The R-410A air conditioner contains one pressure switch to prevent
system operation of the pressures get excessively high. The high
pressure switch opens at 650 psig and closes at 420 psig. The pressure
switch setting is considerably higher than on comparably sized R-22
units. The high pressure switch can be identified by their pink stripe on
the switch’s electrical wires.
The R-410A heat pump contains a loss of charge switch in the liquid line
which opens at 20 psig and closes at 45 psig. See troubleshooting section
for sequence when a pressure switch trip occurs.