Maintenance - Allied Air 4SHP13 Series Installation And Maintenance Instructions Manual

Pressure Switch Circuit
The defrost control includes two pressure switch circuits. A
high pressure switch is connected to the board's HI-PS
terminals (see Figure 13 on page 17). The low pressure, or
loss-of-charge pressure, switch is connected to the LO-PS
terminals.
During a single demand cycle, the defrost control will lock
out the unit after the fifth time that the circuit is interrupted
by any pressure swtich wired to the control board. In addition,
the diagnostic LEDs will indicate a locked-out pressure switch
after the fifthe occurrence of an open pressure switch (see
Table 11). The unit will remain locked out until power to the
board is interrupted, then re-established, or until the jumper
is applied to the TEST pins for 0.5 seconds.
NOTE: The defrost control board ignores input from the
low pressure switch terminals as follows:
During the TEST mode
During the defrost cycle
During the 90-second start-up period
For the first 90 seconds each time the reversing valve
switches heat/cool modes
If the TEST pins are jumpered and the 5-minute delay is
being bypassed, the LO-PS terminal signal is not
ignored during the 90-second start-up period.
Diganostic LEDs
The defrost board uses two LEDs for diagnostics. The LEDs
flash a specific sequence according to the condition as
shown in Table 11.
Defrost Control Board Diagnostic LEDs
Mode
No Power
to Board
Normal Operation/
Power to Board
Anti-Short Cycle
Lockout
Low Pressure
Switch Fault
Low Pressure
Switch Lockout
High Pressure
Switch Fault
High Pressure
Switch Lockout
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Green LED Red LED
OFF
OFF
Simultaneous Slow Flash
Alternating Slow Flash
OFF Slow Flash
ON
OFF
OFF
Slow Flash
OFF
ON
Table 11
Before performing maintenance operations on system,
turn the electric power to unit OFF at disconnect
switch(es). Unit may have multiple power supplies.
Electrical shock could cause personal injury or death.
Before the start of each heating and cooling season, the
following service checks should be performed by a qualified
service technician.
Inspect and clean outdoor and indoor coils. The
outdoor coil may be flushed with a water hose.
NOTE: It may be necessary to flush the outdoor coil
morefrequently if it is exposed to substances which are
corrosive or which block airflow across the coil (such
as pet urine, cottonwood seeds, etc....).
Visually inspect the refrigerant lines and coils for leaks.
Check wiring for loose connections.
Check voltage at the indoor and outdoor units (with
units operating).
Check amperage draw at the outdoor fan motor,
compressor, and indoor blower motor. Values should
be compared with those given on unit nameplate.
Check, clean (or replace) indoor unit filters.
Check the refrigerant charge and gauge the system
pressures.
Check the condensate drain line for free and
unobstructed flow. Clean drain line, if necessary.
Adjust blower speed for cooling. Measure the pressure
drop over the coil to determine the correct blower CFM.
Belt drive blowers: Check drive belt for wwar and
proper tensions.
If insufficient cooling is reported, the unit should be gauged
and refrigerant charge checked (see Refrigerant Charging
on page 12).
Issue 0921

MAINTENANCE

WARNING
506272-01