Armstrong Air Conditioning 4HP13, Installation & Start-Up Instructions

Page: 9 / 17

Page 9 of 17 506318-01 Issue 0946
DEFROST 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.
(OPTIONAL) 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,
coil, and discharge temperature 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.
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.
Sensor
Temperature
Range °F (°C)
Red Led (DS1)
Outdoor
(Ambient)
Coil
Discharge (If
applicable)
Note: Sensor resistance decreases as sensed temperature increases.
Pins/Wire
Color
-35 (-37 to 120
(48)
280,000 to 3750
3 & 4
(Black)
-35 (-37) to 120
(48)
280,000 to 3750
24 (-4) to 350
(176)
41,000 to 103
5 & 6
(Brown)
1 & 2
(Yellow)
Sensor Temp. / Resistance Range