Mitsubishi Electric HP120TNU-A Service Handbook page 141

[5-2 Outdoor Unit Control ]
(3) Stopping the defrost operation
The defrost cycle ends when 12 minutes have passed
have been continuously detected for 4 minutes (when SW4 (916) is set to OFF) or 2 minutes (when SW4 (916) is set to ON)
that exceeds the values in the table below.
The defrost cycle will not end for two minutes once started unless one of the following conditions is met: Pipe temperature
reaches 25°C [77°F] and SW4 (916) is set to OFF OR
In the multiple-outdoor-unit system, defrosting is stopped on all units at the same time.
*1 The compressor frequency is fixed at 60Hz when the compressor bottom SH (TH15 - Te)
mode may continue even after 12 minutes.
*2 (5°C [41°F] 25°C [77°F]).
Model
HP72 - HP120 models
(4) Problems during defrost operation
If a problem is detected during defrost operation, the operation will be stopped, and the defrost prohibition time based on the
integrated compressor operation time will be set to 20 minutes.
The unit will stop after the defrost operation when the total time of "compressor bottom SH (TH15 – Te) 10ºC [18ºF]" reaches
3 minutes.
(5) Change in the number of operating indoor units during defrost operation
Even when there is a change in the number of operating indoor units during defrost operation, the operation will continue, and
an adjustment will be made after the completion of the defrost operation.
Defrost operation will be continued, even if the indoor units stop or under the Thermo-OFF conditions until it has run its course.
16
- chapter 5
*1
since the beginning of the cycle, or when the pipe temperatures (TH3)
*2
=25°C+TH7°C [77°F+TH7°F] and SW4 (916) is set to ON.
TH3
SW4 (916) OFF
7°C [45°F]
10ºC [18ºF]. And the defrost
SW4 (916) ON
12°C [54°F]
HWE18220_GB