Mitsubishi Electric PUHY-200YMF-B Service Handbook page 65

3-2 Back up of frequency control by bypass valve (PUHY-P200·250YMF-B, PURY-(P)200·250YMF-B)
During 20Hz operations, frequency is backed up by turning on (opening) bypass valve (SV2).
• Cooling
During 20Hz operations 3 minutes after starting compressor, bypass valve is turned on when,
Ps is 1.5kg/cm
• Heating
During 20Hz operations 3 minutes after starting compressor, SV2 turned on when high pressure (Pd)
exceeds pressure limit and turned off when Pd falls to 20kg/cm
ON
OFF
(5) Oil return control (Electronic expansion valve <SLEV>)
• Oil return LEV (SLEV) opening is dependent on compressor frequency and ambient temperature.
• SLEV is closed (0) when compressor stops, and SLEV is set (64) for 10 minutes after starting compressor.
(6) Subcool coil control (electronic expansion valve <LEV1>) : PU(H)Y-200·250YMF-B, PUHY-P200·250YMF-B
• 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 60 sec.
• 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 at defrosting.
(7) Defrost operation control
1 PU(H)Y-(P)200·250YMF-B
1) Starting of defrost operations
• After integrated 39 min : P-YMF-B, 50 min : YMF-B of compressor operations, defrosting operations start when –10˚C
or less : P-YMF-B, –2˚C or less : YMF-B of piping temperature (TH5) is detected for 3 consecutive minutes.
• Forcible defrosting operations start by turning on forcible defrost switch (SW2-7) if 3 minutes have already elapsed
after compressor start or completion of defrosting operations.
2) Completion of defrosting operations
Defrosting operations stop when 10 min : P-YMF-B, 15 min : YMF-B have passed since start of defrosting operation,
or piping temperature (TH5) reaches 8˚C or more.
(Defrosting operations do not stop for 2 minutes after starting, except when piping temperature exceeds 20˚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.
2 G (0.15MPa) or less and turned off when Ps is 2.5kg/cm
M
1.5kg/cm 2 G 2.5kg/cm 2
(0.15MPa) (0.25MPa)
2 G (1.96MPa) or less.
ON
M
OFF
G 20kg/cm 2 G
(1.96MPa)
–63–
2 G (0.25MPa) or more.
27kg/cm 2 G
(2.65MPa)