Mitsubishi Electric PUHY-P200 Service Handbook page 73

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 P400-
type and above) has continuously been detected for 3 minutes after the integrated compressor operation
time of 50 minutes have passed.
• If 10 minutes have passed since compressor start-up or since the completion of defrost operation, forced
defrost operation will start by turning on the forced defrost switch (DIPSW2-7).
• 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 15 minutes.
(2) Defrost operation
Compressor frequency
Outdoor unit fan
SV1
SV3 (P450-P650 types only)
21S4a
21S4b
21S4c (P400-P650 types only)
SV5b
SV5c (P400-P650 types only)
LEV1
(3) Completion of defrost operation
• Defrost operation will stop when 12 minutes have past 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 minitues for P400 models 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 minitues for P400 type models 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.
(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 if thermo is turned off, until it has run its
course.
Model No.1 Compressor
P200 type
P250 type
P300 type
P350 type
P400 type
P450 type (50/60Hz)
P500 type (50/60Hz)
P550 type (50/60Hz)
P600 type (50/60Hz)
P650 type (50/60Hz)
480 pulses
- 71 -
No. 2 Compressor
–
72
–
53
–
65
–
65
–
114
110/100 ON (50/60Hz)
110/100 ON (50/60Hz)
110/100 ON (50/60Hz)
110/100 ON (50/60Hz)
110/100 ON (50/60Hz)
Stopped
ON
ON
OFF
OFF
OFF
OFF
OFF