A52x Series Electronic Refrigeration Controller with Adaptive Defrost Technical Bulletin
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Evaporator Fan Operation in Defrost Mode
The Evaporator Fan Drip-Time Delay, Evaporator Fan Temperature Delay, and Evaporator Fan Time Delay settings
affect the behavior of the Evaporator Fan in defrost mode and post-defrost mode. You can set up the post-defrost
evaporator fan behavior with the Evaporator Fan Delay After Defrost feature. The delay time period is 0 to 15
minutes. This feature does not apply if the controller is set to an off-cycle defrost.
Adaptive Defrost Setup Parameters
Expected Defrost Duration
Expected Defrost Duration is an estimate of the time the system requires to fully defrost the evaporator coil and to
reach the defrost termination temperature after a defrost interval. When you set up the Adaptive Defrost feature,
you enter the number of minutes for the Expected Defrost Duration. During operation and changing load
conditions, actual defrost durations may vary in length from your defined Expected Defrost Duration. When this
occurs, the system adjusts the defrost schedule.
Defrost Interval
Defrost Interval is an estimate of the number of hours between the start of consecutive defrost cycles. You enter
the expected Defrost Interval time in hours for the first defrost interval. The Adaptive Defrost feature shortens or
lengthens the Defrost Interval to reach the defrost termination temperature in the expected defrost duration. This
value provides a starting point for the adaptive defrost algorithm.
If the system reaches the defrost termination temperature before the expected defrost duration elapses, Adaptive
Defrost lengthens the next defrost interval. If the system reaches the defrost termination temperature after the
expected defrost duration time elapses, Adaptive Defrost shortens the next defrost interval.
Maximum Time Between Defrosts
Maximum Time Between Defrosts defines the maximum number of hours for any adaptive defrost interval. If the
system calculates a defrost interval that is greater than your defined maximum time, the controller ignores the
calculation and starts the next defrost duration at your defined maximum time.
Minimum Time Between Defrost
Minimum Time Between Defrosts defines the minimum number of hours for any adaptive defrost interval. If the
system calculates a defrost interval that is less than your defined minimum time, the Controller ignores the
calculation and starts the next defrost duration at your defined minimum time.
Blackout Period
You can schedule a daily blackout period for Adaptive Defrost applications, which prevents the occurrence of
defrost cycles during the defined blackout period. Blackout periods are typically scheduled for a regular, predictable
period of high cooling demand. To establish a blackout period for adaptive defrost, you must set up the Blackout
Start Time and Blackout parameters in the Defrost Setup menu flow.
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Blackout Start Time:
This is the time at which the blackout period begins. The adaptive defrost algorithm does
not schedule any defrosts from the start to the end of the blackout period. Edit the real-time value to the time at
which the blackout period starts. The real-time value depends on the Time Format type selected in the Time/
Date screens in the System Setup menu flow.
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Blackout Duration:
This is the number of hours that you add to the Blackout Start Time to form the blackout
period. The blackout period refers to the time interval during which no defrosts occur. Select the number of
minutes for your preferred blackout period duration. The duration starts at the Blackout Start Time.
