Manual 2100-408C
Page
18
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
1/4 inch 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. 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.
FIGURE 11
DEFROST CONTROL BOARD
MIS-1174
