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Temperature switch defrost termination
You can also use a line-voltage temperature defrost termination switch connected to the high-voltage binary input
(HVBIN) terminals to terminate the defrost durations in the refrigeration application. The temperature termination
switch is mounted on the evaporator coil and has a fixed temperature termination value. You do not need to set a
defrost termination temperature value during defrost setup. When the A5xx Controller detects 120 VAC to 240 VAC
across the HVBIN terminals, the controller terminates the defrost duration.
Time-based termination overrides temperature termination
The maximum defrost duration time period overrides both the temperature-sensor and temperature-switch defrost
termination types, if the evaporator does not reach the termination temperature. The defrost duration terminates
when the evaporator reaches the selected defrost termination temperature or the maximum defrost duration
expires, whichever occurs first.
Defrost schedule types
Use the A5xx Controller to schedule routine defrosts or use the adaptive defrost feature. Adaptive defrost
automatically determines the optimal time to initiate the defrost cycles for the refrigeration system.
Scheduled defrost
You can set up a manual or automatic scheduled defrost. Schedule one to eight daily defrost cycles. Use the
manual setting to set the start times for each daily defrost cycle. Using the automatic setting, set only two
parameters; the number of daily defrost cycles and the real-time for the first scheduled defrost. The system
automatically calculates the daily schedule for the defrost intervals. The defrost intervals are of equal length. After
you create a schedule, use the manual option to change one or more of the scheduled start times.
Adaptive defrost
Adaptive defrost adjusts the defrost schedule to achieve a user-defined defrost duration. You set up the expected
defrost duration, the first defrost interval, and a defrost termination temperature. Initially, the system uses the first
defrost interval until it learns to adapt to the existing conditions. The adaptive defrost system adjusts the length of
the defrost interval so that the expected defrost duration coincides with the time that the evaporator reaches the
termination temperature. For adaptive defrost to take place, mount the Sn2 defrost sensor or the HVBIN defrost
termination switch on the evaporator. The defrost sensor or switch determines when the defrost duration is
complete. For more information, see
Adaptive defrost setup parameters
.
Compressor and evaporator fan start delays
To control the operation of the compressor and evaporator fan, set up the following time delay features on the A5xx
Controller:
• Compressor anti-short cycle delay (ASD)
• Evaporator fan drip-time delay
• Evaporator fan time delay
When the controller is in a delay period, the UI message field displays the delay type and the number of minutes
that remain in the delay period.
Anti-short cycle delay
The ASD maintains the compressor relay off (contacts open) for a period of time after the relay cycles off. This
delay prevents the compressor from cycling back on quickly after it has cycled off. Select from 0 minutes to 12
minutes for the ASD. The following figure provides more information about how the ASD overrides the load
demand to maintain the compressor relay off.
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