Manual Defrost
How to manually start a defrost cycle on the unit
With the unit powered up (START/RUN-OFF switch in START/RUN) and the default screen displayed, press the MANUAL DEFROST key. If you are not on the default screen, press the BACK or EXIT soft key first.
This procedure may be demonstrated in PC mode, but the unit will not actually enter defrost.
If conditions for defrost are met, the status bar and Box Temperature display will change to "DEFROST". The MessageCenter will display "DEFROST CYCLE STARTED" for 10 seconds.
If conditions are not met, the MessageCenter will display "CANNOT START DEFROST CYCLE" for 5 seconds. Check the conditions listed below and retry when cleared.
A manual defrost cannot start when: • The box temperature is too warm or coil temperatures indicate defrost is not needed — the host unit only allows defrost when the defrost termination temperature sensor is below 40°F (4.4°C) • Remote evaporators will allow defrost when the DTT sensor is above 40°F (4.4°C) only if other coil temperature readings indicate a defrost may be needed • The engine has not run at least 15 seconds after starting • The unit is in PC mode • The unit is in Pretrip • There is an active shutdown alarm
Defrost may also start automatically at preset intervals via the system defrost timer or the defrost air switch. You do not need to take any action for automatic defrost cycles.
Defrost ends when all defrost termination temperature (DTT) sensors rise above 55°F (12.8°C). On remote evaporators, if the DTT is above 25°F (−3.9°C) at the start of defrost, termination occurs after the DTT rises 35°F (19.4°C) (max 80°F) or when the EVOT rises above a maximum threshold indicating the coil is defrosted.
If the defrost cycle does not end within 45 minutes, it is terminated automatically and "DEFROST NOT COMPLETE" will display in the MessageCenter. The system will then wait 1.5 hours of compressor running time before attempting another automatic defrost cycle.
Pressing the MANUAL DEFROST key will override the 1.5-hour wait period and start a new defrost cycle immediately, as long as all defrost conditions are met.