Control For Heating Operation At Low Outdoor Air Temperature - Daikin RTSQ20PY1 Service Manual

SiBE31-801_C
6.6 Control for Heating Operation at Low Outdoor Air
Temperature
To conduct optimal heating operation, the two operation modes, "Two-stage compression" and
"Single-stage compression", are available according to outdoor temperatures and loads.
Function
*Determine at startup whether to conduct single-stage compression or two-stage compression.
· Outdoor temp. < 5°C
&
· Capacity of indoor unit
with thermostat ON
> 7.1 to 11.2kW
· Outdoor temp. ≥ 7°C
· Function unit compressor = 52Hz
· &
· Outdoor unit compressor
< 104Hz + OFF + OFF
OR
· Pc > 3.3MPa
· When (Indoor unit operating capacity ×
Function unit compressor operating capacity)
comes less than a certain value
System startup
Determination of operation mode
OR
Two-stage compression
· Outdoor temp. < 5°C
· Capacity of indoor unit
with thermostat ON
> 7.1 to 11.2 kW
&
· Outdoor unit compressor
> 112Hz + OFF + OFF
· A lapse of 2 min.
Single-stage compression
Normal Operation
· Outdoor temp. ≥ 5°C
· Capacity of indoor unit
with thermostat ON
≤ 7.1 to 11.2kW
96