Allied 4SHP16 Manual de instrucciones de instalación - Página 15
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Imprimir páginaDefrost Board Pressure Switch Connections
The unit's automatic reset pressure switches (LO PS - S87
and HI PS - S4) are factory-wired into the defrost board on
the LO-PS and HI-PS terminals, respectively.
Low Pressure Switch (LO-PS) — When the low pressure
switch trips, the defrost board will cycle off the compressor,
and the strike counter in the board will count one strike.
The low pressure switch is ignored under the following
conditions:
•
during the defrost cycle and 90 seconds after the
termination of defrost
•
when the average ambient sensor temperature is
below 15° F (-9°C)
•
for 90 seconds following the start up of the compressor
•
during "test" mode
High Pressure Switch (HI-PS) — When the high pressure
switch trips, the defrost board will cycle off the compressor,
and the strike counter in the board will count one strike.
Defrost Board Pressure Switch Settings
High Pressure (auto reset) - trip at 590 psig; reset at 418.
Low Pressure (auto reset) - trip at 25 psig; reset at 40.
5-Strike Lockout Feature
The internal control logic of the board counts the pressure
switch trips only while the Y1 (Input) line is active. If a
pressure switch opens and closes four times during a Y1
(Input), the control logic will reset the pressure switch trip
counter to zero at the end of the Y1 (Input). If the pressure
switch opens for a fifth time during the current Y1 (Input),
the control will enter a lockout condition.
The 5-strike pressure switch lockout condition can be reset
by cycling OFF the 24-volt power to the control board or by
shorting the TEST pins between 1 and 2 seconds. All timer
functions (run times) will also be reset.
If a pressure switch opens while the Y1 Out line is engaged,
a 5-minute short cycle will occur after the switch closes.
Defrost System Sensors
Sensors connect to the defrost board through a field–
replaceable harness assembly that plugs into the board.
Through the sensors, the board detects outdoor ambient
and coil fault conditions. As the detected temperature
changes, the resistance across the sensor changes.
Sensor resistance values can be checked by ohming
across pins.
NOTE: When checking the ohms across a sensor, be
aware that a sensor showing a resistance value that is not
within the range shown, may be performing as designed.
However, if a shorted or open circuit is detected, then the
sensor may be faulty and the sensor harness will needs to
be replaced.
507919-01F
Temperature
Sensor
Range °F (°C)
Outdoor
-35 (-37) to
(ambient)
-35 (-37) to
Coil
NOTE: Sensor resistance decreases as sensed temperature
increases.
Table 4. Sensor Temp. / Resistance Range
Coil Sensor—The coil temperature sensor considers
outdoor temperatures below -35°F (-37°C) or above
120°F (48°C) as a fault. If the coil temperature sensor is
detected as being open, shorted or out of the temperature
range of the sensor, the board will not perform demand
or time/temperature defrost operation and will display the
appropriate fault code. Heating and cooling operation will
be allowed in this fault condition.
Ambient Sensor—The ambient sensor considers outdoor
temperatures below -35°F (-37°C) or above 120°F (48°C)
as a fault. If the ambient sensor is detected as being open,
shorted or out of the temperature range of the sensor,
the board will not perform demand defrost operation. The
board will revert to time/temperature defrost operation and
will display the appropriate fault code. Heating and cooling
operation will be allowed in this fault condition.
NOTE: Within a single room thermostat demand, if 5-strikes
occur, the board will lockout the unit. Defrost board 24 volt
power "R" must be cycled "OFF" or the "TEST" pins on
board must be shorted between 1 to 2 seconds to reset
the board.
Defrost Temperature Termination Shunt (Jumper)
Pins—The defrost board selections are: 50, 70, 90, and
100°F (10, 21, 32 and 38°C). The shunt termination pin
is factory set at 50°F (10°C). If the temperature shunt is
not installed, the default termination temperature is 90°F
(32°C).
Delay Mode
The defrost board has a field-selectable function to reduce
occasional sounds that may occur while the unit is cycling
in and out of the defrost mode. When a jumper is installed
on the DELAY pins, the compressor will be cycled off for
30 seconds going in and out of the defrost mode. Units are
shipped with jumper installed on DELAY pins.
NOTE: The 30 second compressor delay feature (known
as the quiet shift) must be deactivated during any unit
performance testing. The feature is deactivated by
removing the jumper located on the compressor delay pins
on the control board mounted inside the unit control box.
This feature is optional for the homeowner, but may impact
testing performance.
Issue 1846
Red LED
(DS1)
280,000 to
120 (48)
3750
280,000 to
120 (48)
3750
Pins / Wire
Color
3 & 4
(black)
5 & 6
(brown)
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