7
2.8
Defrost Cycle
The defrost heater is controlled by the control module, which switches it via a relay.
The defrost interval can vary from between 8 hours of compressor run time to 16
hours of compressor run time, depending on the duration time of the last defrost.
When the control module switches the compressor off for a defrost, there is a 2
minute delay before the defrost heater is turned on. The defrost is terminated when
the defrost sensor reaches +8
O
C. At the conclusion of the defrost, there is a 4
minute delay after the defrost element has been turned off before the compressor is
turned on.
Defrost Cycle
Normal Run
Normal Run
Warm up time
Drip time
Compressor switches off
Defrost element
switches on
Defrost element switches off at +8
o
C
Compressor switches
back on
2 minute
delay
30 minutes Maximum defrost time
4 minute
delay
Defrost Cycle
2.9
PC Heater
The PC heater is located behind the cooling plate. The heater is connected directly
to the control module.
2.10 Temperature Controller
A control, consisting of a variable resistor, located in the control box is used to set the
desired temperature. The resistance range of this resistor is from 0
Ω
to 1K
Ω
. The
PC evaporator temperature range varies between -17.5
O
C at the lowest setting of 1,
to –28
O
C at the highest setting on 7. Mid setting of 4 is -23.5
O
C.
2.11 Fault Alarm
If the control module detects a fault, which it is unable to recover, an alarm is
sounded. The alarm only comes on when the PC door is opened. The numbers of
beeps indicate the fault code. (Refer Fault Codes, Section 3.)
If the door is closed, the alarm discontinues until the door is opened again.
2.12 Compressor Starting
The compressor is started by the control module. It is a timed start, therefore if the
compressor does not start within 1 second, the controller will cancel the start. If the
compressor draws too much current, the overload will activate and cut power to the
compressor.
