Firmware V3.15
21.04.2021
32/401
5.5.2 Defrost in general
Defrosting prevents icing of the evaporators due to normal control action. Defrosting is performed by
supplementary heating of the evaporator by the off-cycle method. Refrigeration point temperature control is
deactivated during defrosting. Defrosting differs for single-zone and two-zone operation.
Defrosting in single-zone operation
R1.x: Evaporator sensor (with UA 121, UA 131, UR 141 NK/TK, UA 131 DD these sensors are used for
defrosting)
R2.x: Supply air sensor (with UA 111, UA 111 D, UA 141) these sensors are used for defrosting)
Solenoid valve 1: Relay for Solenoid Valve 1
Defrost heater 1 to 4: Relay for Defrost Heater 1 to 4 (depending on controller type)
Allocation of sensors to defrost relays
Optional, non-connected sensors are not used for operation of the defrost relays.
Controller type
Required sensors
Allocated defrost relay
UA 111 / UA 111 D / UA 141
R2.1 R2.2 R2.3 R2.4 (R2.5 with UA 111 D only)
Defrost relay 1
–
Defrost relay 2
UA 121
R1.1 R1.2 R1.3 R1.4
Defrost relay 1
–
Defrost relay 2
UA 131 / UA 131 DD
R1.1
Defrost relay 1
R1.2
Defrost relay 2
R1.3
Defrost relay 3
R1.4
Defrost relay 4
UR 141 NK(NT) / UR 141 TK(LT)
R1.1 R1.2
Defrost relay 1
R1.3 R1.4
Defrost relay 2
Summary of Contents for UA 400
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Page 361: ...Firmware V3 15 21 04 2021 361 401 FANS 2 Pos XXXXX Fan Delay Fan delay ...
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