Manual 2100-742A
Page
29 of 54
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 defrost control board. 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.
FIGURE 23
Defrost Control Board
Model
Setting
Q24H4
30
Q30H4
30
Q36H4
30
120*
SW
1
SW
2
TIME (SEC)
OFF
OFF
ON
ON
OFF
ON
OFF
ON
30
60
180
OFF
MIS-4228
LOW PRESSURE BYPASS TIMER SWITCH
*(FACTORY SETTING 120 SECONDS)
ACCUMULATED DEFROST TIME TIMER
(FACTORY SETTING 30 MIN.)
ON
