Defrost Operation Control - Mitsubishi Electric PFD-P250 Service Handbook

[ III Control ]

-5- Defrost Operation Control

(1) Starting the defrost operation
Defrost operation is started when the pipe temperature (TH5) of -10°C or below (-8°C or below for P500-type) has con-
tinuously been detected for 3 minutes after the integrated compressor operation time of 50 minutes have passed (90 min-
utes when the defrost prohibit timer is set to 90 minutes).
If 10 minutes have passed since compressor start-up or since the completion of defrost operation, forced defrost opera-
tion will start by turning on the forced defrost switch (DIP SW2-7).
Even if the defrost prohibit timer is set to 90 minutes, the actual defrost prohibit time for the next operation will be 50
minutes if defrosting took 12 minutes.
(2) Defrost operation
Compressor frequency
Outdoor unit fan
SV1
SV3 (P500 model only)
21S4a
21S4b (P500 model only)
SV4c (P500 model only)
21S5b (P500 model only)
21S5c (P500 model only)
LEV1
(3) Stopping the defrost operation
Defrost operation will stop when 12 minutes have passed since the beginning of defrost operation (15 minutes when the
defrost prohibit timer is set to 90 minutes), or when the piping temperature (TH5) of 10°C or above has been continuously
detected for 2 minutes (TH5 above 7°C for 2 minutes for P500 model and above).
Defrost operation will not stop its operation for 2 minutes once started unless the piping temperature exceeds 25°C within
2 minutes, in which case the operation will stop (Above 20°C within 2 minutes for P500 model and above).
(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.
Model No.1 Compressor
P250 model
P500model
(50/60 Hz)
- 22 -
No.2 Compressor
53
70/60
Stopped
ON
ON
OFF
OFF
OFF
OFF
OFF
480 pulses
-
ON (50/60 Hz)