Specifications

Si01-406 Control for Heat Pump Models
Functions and Control 45
3.8 Liquid Compression Protection Function 1 (Securing of
Differential Pressure and Blown Air Temperature)
Outline To secure the reliability of the compressor (for dryness of suction refrigerant and differential
pressure) which is the primary purpose of the compressor, the lower limit of the output
frequency is limited to two stages under the condition of outside air temperature. This time, in
addition to this purpose, this function is adopted also for prevention of cold draught by securing
the blown air temperature at the time of heating operation by low-temperature out side air.
Processing 1. At the first step
 During operation of compressors.
 Outdoor temperature
≤
DOA1CG

If  and  are under the simultaneous condition with AND, the lower limit of frequency in
this function is set at FCG7.
 Compressors stop.
 Outdoor temperature
≥
DOA2CG

If  and  are under the simultaneous condition with OR, the lower limit of frequency at the
first step control is cancelled.
2. At the second step
 During operation of compressors
 Outdoor temperature
≤
DOA3CG

If  and  are under the simultaneous condition with AND, the lower limit of frequency in
this function is set at FCG8.
 Compressors stop.
 Outdoor temperature
≥
DOA4CG

If  and  are under the coordinate condition with OR, the lower limit of frequency at the
second step control is cancelled.
3. The set of a constant
DOA1CG, DOA2CG, DOA3CG, FCG7 and FCG8 have constants for Cooling / Heating
separately and these constants are distinguished with a suffix c/w.
4. Actual constant
∗
DOA : Outdoor air temperature
CGC : Compressor guard for cooling
CGW : Compressor guard for heating
FCG : Frequency guard for compressor protection
∗
Common setting for 25 / 35 class
Cooling Heating
DOA1CGC 18°CDOA1CGW0°C
DOA2CGC 20°CDOA2CGW2°C
DOA3CGC 14°CDOA3CGW–4°C
DOA4CGC 16°CDOA4CGW–2°C
FCG7C 34 Hz FCG7W 34 Hz
FCG8C 34 Hz FCG8W 34 Hz
FCG8
The lower
frequency limit.
Cancelled FCG7 FCG7Cancelled
DOA3CG
DOA4CG
DOA1CG
DOA2CG
Outdoor temperature
(R1044)