Mitsubishi Electric CITY MULTI PUHY-P200YEM-A Service Handbook page 57

(5) Subcool coil control (electronic expansion valve <LEV1>) : PUHY-(P)200·250·315
• The amount of super heat detected from the bypass outlet temperature of subcool coil (TH8) is controlled to be
within a certain range for each 30 seconds.
• The opening angle is corrected and controlled depending on the outlet/inlet temperature of subcool coil (TH5, TH7)
and the discharge temperature.
• However, the valve will be closed (0) at heating and compressor stopping.
• It will fully open during defrosting.
(6) Defrost operation control
1 PU(H)Y-(P)200·250·315
1) Starting of defrost operations
• After integrated 39 minutes : The compressor operations, defrosting operations start when – 10˚C(R407C),
– 6˚C(R22)piping temperature (TH5) is detected for 3 consecutive minutes.
• Forcible defrosting operations start by turning on forcible defrost switch (SW2-7) if 10 minutes have already elapsed
after compressor star
• Defrost prohibit timer
Minimum consecutive running minutes to defrost can be increaced from 39 minutes to 90 minutes by setting SW2-8 "ON".
Defrost will last a maximum of 15 minutes. Then next defrost time will be 39 minutes.
2) Completion of defrosting operations
Defrosting operations stop when 10 minutes : It has passed since start of defrosting operation,
or piping temperature (TH5) reaches 10˚C or more.
(Defrosting operations do not stop for 2 minutes after starting, except when piping temperature exceeds 25˚C.)
3) Defrosting prohibition
Defrosting operations do not start during oil recovery, and for 10 minutes after starting compressor.
4) Trouble during defrosting operations
When trouble is detected during defrosting operations, the defrosting operations stop, and defrosting prohibition
time decided by integrated operation time of compressor is set to be 20 minutes.
5) Change in number of operating indoor units during defrosting operations
• In case number of operating indoor units changes during defrosting operations, the defrosting operations continue,
and control of unit number change is performed after the defrosting operations are finished.
• Even in case all indoor units stop or thermostat is turned off during defrosting operations, the defrosting operations
do not stop until expected defrosting activities are completed.
t or completion of defrosting operations and will last for 10 minutes.
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