Manual 2100-549Q
Page
34 of 69
If some abnormal or temporary condition such as a high
wind causes the heat pump to have a prolonged defrost
cycle, the heat pump control will restore the system to
heating operation automatically after 8 minutes.
The heat pump defrost control board has an option of
30, 60 or 90-minute setting. All models are shipped
from the factory on the 90-minute pin. If special
circumstances require a change to another time,
remove the wire from the 90-minute terminal and
reconnect to the desired terminal.
The manufacturer’s recommendation is for 90-minute
defrost cycles. Refer to Figure 20.
There is a cycle speed up jumper on the control. This
can be used for testing purposes to reduce the time
between defrost cycle operation without waiting for
time to elapse.
Use a small screwdriver or other metallic object,
or another ¼" QC, to short between the
SPEEDUP
terminals to accelerate the HPC timer and initiate
defrost.
Be careful not to touch any other terminals with the
instrument used to short the
SPEEDUP
terminals.
It may take up to 15 seconds with the
SPEEDUP
terminals shorted for the speedup to be completed and
the defrost cycle to start.
As soon as the defrost cycle kicks in remove the
shorting instrument from the SPEEDUP terminals.
Otherwise the timing will remain accelerated and
run through the 1-minute minimum defrost length
sequence in a matter of seconds and will automatically
terminate the defrost sequence.
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" QC terminal works best) the defrost sensor mounted
on the outdoor coil is shunted out and 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 artificial 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.
120*
SW
1
SW
2 TIME (SEC)
OFF
OFF
ON
ON
OFF
ON
OFF
ON
30
60
180
MIS-2668 A
OFF
LOW PRESSURE BYPASS TIMER SWITCH
*(FACTORY SETTING 120 SECONDS)
ACCUMULATED DEFROST TIME TIMER
(FACTORY SETTING 60 MIN.)
ON
(FACTORY SETTING 90 MIN.)
FIGURE 20
Defrost Cycle
