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Manual 2100-455M
Page 20 of 28
There is an initiate defrost jumper (sen jump) on the
control that can be used at any outdoor ambient during
the heating cycle to simulate a 0° coil temperature.
This can be used to check defrost operation of the unit
without waiting for the outdoor ambient to fall into the
defrost region.
By placing a jumper across the SEN JMP terminals (a
¼ inch QC terminal works best) the defrost sensor
mounted on the outdoor coil is shunted out & will
activate the timing circuit. This permits the defrost cycle
to be checked out in warmer weather conditions without
the outdoor temperature having to fall into the defrost
region.
In order to terminate the defrost test the SEN JMP jumper
must be removed. If left in place too long, the compressor
could stop due to the high pressure control opening
because of high pressure condition created by operating in
the cooling mode with outdoor fan off. Pressure will rise
fairly fast as there is likely no actual frost on the outdoor
coil in this articial test condition.
There is also a 5-minute compressor time delay function built
into the HPC. This is to protect the compressor from short
cycling conditions. The board’s LED will have a fast blink
rate when in the compressor time delay. In some instances,
it is helpful to the service technician to override or speed up
this timing period, and shorting out the SPEEDUP terminals
for a few seconds can do this.
Low Pressure Switch Bypass Operation - The control has
a selectable (SW1) low pressure switch bypass set up to
ignore the low pressure switch input during the rst (30,
60, 120 or 180 seconds) of “Y” operation.
After this period expires, the control will then monitor the
low pressure switch input normally to make sure that the
switch is closed during “Y” operation.
High Pressure Switch Operation - The control has a
built-in lockout system that allows the unit to have the
high pressure switch trip up to two times in one hour and
only encounter a “soft” lockout. A “soft” lockout shuts
the compressor off and waits for the pressure switch to
reset, which at that point then allows the compressor to
be restarted as long as the 5-minute short cycle timer
has run out. If the high pressure switch trips a third time
within one hour, the unit is in “hard” lockout indicating
something is certainly wrong and it will not restart itself.