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External defrosting without master-slave mode: The external defrost signal must be active for the maximum
duration of defrosting. Accordingly the external defrost signal assumes the internal defrost function of Safe
Defrost Time. Defrosting is however terminated regardless of the defrost signal being active when defrost
termination temperature is exceeded on the defrost sensors.
External defrosting with master-slave mode: The external defrost signal may only be applied only briefly, as in
this instance it is only used to initiate defrosting. Maximum defrost duration is again governed by the internal
Safe Defrost Time parameter (Menu 3-2). The defrost signal must always be shorter than the internal safe
defrost time (minimum 10 sec, preferably not longer than 5 min).
By command signal via CAN bus (manual or higher-level control e.g. Combi Gateway)ineveryinstance,
defrosting is not initiated unless the conditions for defrosting are found to be fulfilled. These are:
Evaporator temperature lower than defrost termination temperature
In demand defrosting, defrost counter set to 1
With defrost initiation by internal clock, a new defrost cycle cannot be initiated before the safe defrost time
has expired regardless of defrosting being previously terminated by evaporator temperature.
By command from the pack controller via CAN bus (UA 131 DD, UR 141 TK (LT) only):
Defrosting (discharge gas defrosting) is initiated without checking for conditions.
1.
2.
With controller types UA 121, UA 131 and UR 141 TK (LT) defrosting will also be inhibited when the
following conditions are all met:
Temperature alarm is active or alarm delay is set to 0 minutes.
Evaporator temperature R1.1 or R1.3 is higher than the defined return air setpoint.
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