–43–
(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 No. 1 compressor and the ambient temperature; in heating, by the operating capacity of No. 1 compressor.
• It is opened at 64 pulses when both compressors have stopped or started for the duration of 10 minutes. (Upper limit
of LEV opening is So = 388 pulse.)
• SLEV = 0 when the No. 1 compressor has stopped.
(6)
Defrosting control
1) Starting defrosting
• After the heating operation has been in operation for 50 minutes or after 90 minutes has passed and the piping
temperature (TH5) has detected –8
°
C or below, defrosting operation 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 becomes active.
2) End of defrosting
• Defrosting ends when 12 minutes have passed since the start of defrosting, or when the piping temperature (TH5
and TH7) has remained at or above 7
°
C 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.
• Termination of defrosting process 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 process is stopped and the defrost-suspension time is set at
20 minutes of cumulative compressor operation time.
5) Change in the number of operating indoor units while defrosting
• Even if the number of operating indoor units changes while the outdoor unit is defrosting, the defrosting operation
continues. Once defrosting has ended, control for changing the number of units is performed.
• Even if the indoor unit is stopped while the outdoor unit is defrosting or if the thermostat is turned off, the defrosting
operation continues. Once defrosting has ended, the unit will stop.
6) Number of compressors operating during defrosting
• The number of compressors in operation during defrosting is always two.
(7)
Control of liquid-level detecting heater
The function is to detect the refrigerant liquid level in accumulator, and heat refrigerant with liquid-level heater to judge
refrigerant amount. Seven steps of duty control are applied to liquid-level heater, depending on frequency and outdoor
air temperature. Control begins one-minute after starting compressor.