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verify system operation and compatibility with the
heat pump. Refer to the installation instructions
for this equipment and perform a functional
checkout in accordance with the manufacturer’s
instructions.
Indoor Blower
1. Turn the fan mode to ON. Verify that the
indoor blower is operating and that airfl ow is
not restricted.
2. Set the fan mode back to AUTO. Blower will
operate at a decreased speed on continuous
fan.
Short Cycle Protection
1. With the system operating in COOLING mode,
record the setpoint temperature setting of the
thermostat.
2. Gradually raise the setpoint temperature
until the outdoor unit and indoor blower de-
energize.
3. Immediately lower the setpoint temperature of
the thermostat to its original setting and verify
that the indoor blower is energized and that
the outdoor unit remains de-energized.
4. After approximately 3 minutes, verify that the
outdoor unit energizes and the temperature
of the air supplied to the facility is cooler than
ambient temperature.
Defrost Cycle Control
The defrost cycle is controlled by an Adaptive
Demand Defrost algorithm that monitors coil
temperature and ambient temperature. Other
features of the of the demand defrost board
include:
• 4 Field selectable defrost termination
temperatures (50° F - 80° F coil temperature).
• Field selectable compressor delay feature.
• High pressure and low pressure switches.
• Sensing of second stage compressor demand.
• Test/speed up capability.
• Anti short cycle timer (3 minutes) for
compressor protection.
• On board diagnostics with fl ashing LED for
quicker troubleshooting. See Table 2.
Diagnostic Description LED Status
Control Fault (No Power) Off
Normal Operation On
ASCD Delay Active
(with compressor demand)
1 Flash
Low Pressure Switch Lockout 2 Flashes
High Pressure Switch Lockout 3 Flashes
Ambient Sensor Fault 4 Flashes
Coil Sensor Fault 5 Flashes
Table 2. Control Diagnostic
Control is uncalibrated when power is applied.
Calibration occurs after a defrost cycle. The
control initiates this sacrifi cial defrost after 34
minutes of accumulated compressor run time in
heating with coil temperature below 35° F. The
defrost cycle terminates if coil sensor reaches
selected termination temperature or after 14
minutes defrost.
Defrost function is disabled if coil temperature
is above 35° F. If Ambient sensor is detected as
open or shorted, demand defrost will not operate
and control will revert to time/temperature defrost
operation. If the outdoor coil sensor is detected
as open or shorted, the control will not perform
demand or time/temperature defrost operation.
NOTE: When the defrost cycle initiates, there
will be a 30 second compressor delay going into
and out of the defrost cycle. This delay may be
removed by removing P6 connector on the board.
This 2-stage unit will defrost in second stage
regardless of the stage called for by the
thermostat.
NOTE: All units are shipped from the factory with
the default termination temperature set at 70° F.
Defrost Test Procedure
1. Terminals R - C must have 18-30VAC present
between them in order for defrost sequences
to be initiated.
2 With heat mode thermostat demand (Y
connected to R), short and hold the TEST
pins together. This will energize reversing
valve to initiate a forced defrost. NOTE: This
will bypass the ASCD and allow the high stage
compressor to come on immediately (if the
REMOVE FOR NO DELAY jumper at P6 is
removed). If the REMOVE FOR NO DELAY
jumper at P6 is installed, the compressor will
energize immediately following a 30-second
delay.
3. Remove the short on the TEST pins.
• If the Coil temperature is above the Terminate
Temperature selection setting, the defrost
cycle will be terminated (reversing valve will
de-energized).
• If the coil temperature is below the Terminate
Temperature election setting, the defrost
cycle will continue for 14 minutes or until the
coil temperature rises above the Terminate
Temperature selection setting. NOTE: Short
the TEST pins for 1 second or more to force
the control out of defrost and back to heating
mode (reversing valve de-energized).
Compressor will turn on immediately (if
the REMOVE FOR NO DELAY jumper is
removed).