Continuous Heating Mode Control - Mitsubishi Electric PUHY-P200 Service Handbook

[5-2 Outdoor Unit Control ]
(3) Stopping the defrost operation
The defrost cycle ends when 12 minutes have passed since the beginning of the cycle, or when the pipe temperature (TH3)
has 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
*1 (5°C [41°F] 25°C [77°F]).
In the multiple-outdoor-unit system, defrosting is stopped on all units at the same time.
Model
P200 -P250 models
P300 - P500 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.
(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.
5-2-8

Continuous heating mode control

(1) Continuous heating mode start conditions
Continuous heating mode will start when all the conditions listed in the table below are met (outside temperature, cumulative
compressor operation time, and piping temperature).
SW4 (848) must be set to ON to perform Continuous heating mode.
Outside temperature (TH7)
Cumulative compressor operation
time
Evaporating temperature (Te)
(2) Valve operation during Continuous heating cycle
Outdoor unit fan
SV1a
SV5b
SV9
SV10
SV11
21S4a,b,c
HWE14040
*1
=25+TH7°C [77°F+TH7] and SW4 (916) is set to ON.
TH3
SW4 (916) OFF
10°C [50°F]
7°C [45°F]
2.0 °C [35.6 °F] to 7.0 °C [44.6 °F]
After 10 minutes at 2.0 °C [35.6 °F] to 3.5 °C [38.3 °F] has elapsed
After 20 minutes at 3.6 °C [38.5 °F] to 7.0 °C [44.6 °F] has elapsed
After 3 minutes at 0°C [32°F] to -25 °C [-13°F] has elapsed
Top (right) HEX in defrost cycle
In operation
OFF
ON
- 97 -
SW4 (916) ON
5°C [41°F]
5°C [41°F]
Bottom (left) HEX in defrost cycle
In operation
OFF
OFF
OFF
ON
OFF
ON
GB