MITSUBISHI ELECTRIC P500YMF-C - Manual (Page 45)

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(5) Oil return control (Electronic expansion valve (SLEV))
• The amount of opening of the oil-return LEV (SLEV) is determined as follows: in cooling, by the operating capacity
of the No. 1 compressor and the ambient temperature; in heating, by the operating capacity of the No. 1 compressor.
• It is opened (64pulses) when both compressors are stopped and started for 10 minutes. (Upper limit of LEV opening
is So = 388 pulse.)
• SLEV = 0 when the No. 1 compressor is stopped.
(6) Defrosting control
1) Start of defrosting
• After there has been heating operation for 50 minutes or after 90 minutes has passed and a piping temperature
(TH5) of – 8
°
C or less is detected for a preset time, defrosting begins.
• When 10 minutes has passed since the compressor began operation or for forced defrosting (Setting of Dip SW2-
7 on) when 10 minutes has passed since recovery from defrosting forced defrost mode recomes active.
2) End of defrosting
• Defrosting ends when 12 minutes have passed since the start of defrosting, or when a piping temperature (TH5 and
TH7) of 7
°
C or more is detected for 4 minutes or longer. (Note that if the defrost-prohibited time is set on 90 minutes,
the defrost-prohibit time will be 50 minutes following a 12-minute timed recovery.
• Ending the defrosting is prohibited for 4 minutes after the start of defrosting.
3) Defrost-prohibit
• Defrosting is not performed for 10 minutes after the start of compressor operation and during oil recovery mode.
4) Abnormalities during defrosting
• If an error is detected during defrosting, the defrosting is stopped and the defrost-prohibit time is set to 20 minutes
by the compressor cumulative operating time.