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7-2. Protective Functions
7-2-1. Defrost Detection and Release
(2) Clean defrost
If all indoor units are stopped during HEAT operation, and frost is detected at the L1 line, and the
conditions for defrost are met, then defrost operation occurs, and the unit stops after defrost is completed.
(1) Non-stop defrosting
Heating operation
NOTE
Defrost does not occur during HIGH POWER operation.
If other stopped indoor units are started during defrost operation, they begin operating in
defrost mode.
Frost detection
Non-stop defrosting
Releasing of defrosting
Defrosting sequence 4-way valve ON
Defrost detection occurs in either of the following cases:
The temperature of the heat exchanger remains at or below
the L1 line for 35 minutes after the start of HEAT operation.
Compressor
Outdoor fan
Solenoid valve
(for hot gas bypass)
Temperature of the outdoor heat exchanger is at or above the
temperature shown in the table below.
Temperature of releasing
*1 The temperature for releasing of defrosting is (68 °F) or higher when the
outdoor air temperature is less than 32 °F.
Defrost operation time
Defrost operation has continued for 12 minutes (max. length).
Indoor fan
(80 Hz) operation (4-way valve ON)
OFF
ON
OFF
The temperature of the heat exchanger remains at or below
the L2 line for 120 minutes after the start of HEAT operation.
Outdoor heat
exchanger temperature (°F)
Outdoor air
temperature (°F)
(- 4) 0
( 21.2)
( 19.4)
(-11.2)
(-13.0)
L2
L1
Less than 2 minutes 2 minutes or more
No releasing 57.2 °F or higher (*1)
The numerical values such as temperature, frequency, time and current in parentheses are an example
of CU-4KE31NBU and the values are different from the other models.
NOTE
Heat exchanger
temperature for
releasing defrosting
77