PACD011001C2 Outline of Control
Function UM Combination “MA1R Series” Using R-407C 437
3.1.11 Low Pressure Protection Control
The following control is provided to protect the compressors from abnormal decrease of low pressure (LP).
Normal operation
Normal operation
E4 malfunction
stop
Forced thermostat
OFF
LP<0.15MPa
LP<0.05MPa
LP>0.10MPa
LP<0.03MPa LP<0.0MPa
Compressor
operation
frequency
31Hz+OFF+OFF
LP<0.05MPa
SVP (for hot gas
bypass) : ON
LP<0.08MPa
SVP (for hot gas
bypass) : OFF
SVP (for hot gas
bypass) : ON
OR
·&
·Ta<Tes+5
·LP>0.20MPa
·30 sec elapse
OR
·&
·&
·LP>0.13MPa
·Ta>5˚C
·LP<0.098MPa
·Ta≤5˚C
OR
·&
·&
·LP<0.08MPa
·Ta>5˚C
·LP<0.049MPa
·Ta≤5˚C
∗ Malfunction reset
LP>0.09MPa
LP>0.10MPa
(Monitoring LP every 30 sec.)
LP>0.07MPa
(Monitoring LP every 1 min)
Ta : Outdoor air temp. (˚C)
Tes : Low pressure equivalent
saturation temp. (˚C)
[Heating mode]
[Cooling mode]
SVP (for hot
gas bypass) : ON
LP > 0.13 MPa
Upper limit frequency =
Maximum frequency
1-step increase for
compressor
operation frequency
[Oil return mode (common for cooling / heating)]
Restriction for upper
limit compressor
operation frequency ∗1
(V0822)
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