Mitsubishi Electric City Multi PQHY-P72 Service Handbook page 143

[ VII Control ]
-8- Heat Source Unit Heat Exchanger Capacity Control <PQRY>
(1) Control method
Heat exchanger capacity is controlled by the solenoid valve (SV4a-4d,7a-7c) to keep constant the evaporating temper-
ature (0°C[32°F]=0.71MPa[103psi]) during cooling operation and condensing temperature
(49°C[120°F]=2.88MPa[418psi]) during heating operation.
(2) Heat exchanger capacity control patterns
Operation
mode
SV4a
Cooling ON
only
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
Cooling ON
main
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
Solenoid valve
SV4b SV4c SV4d
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
OFF ON OFF
OFF ON OFF
OFF ON ON
OFF OFF OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
ON ON OFF
OFF ON OFF
OFF ON OFF
OFF ON ON
OFF OFF OFF
OFF OFF OFF
OFF OFF ON
- 134 -
SV7a SV7b SV7c
ON OFF OFF
ON ON OFF
ON OFF OFF
ON ON OFF
ON OFF OFF
ON ON OFF
ON OFF OFF
OFF OFF OFF
OFF ON OFF
OFF OFF OFF
OFF ON OFF
OFF OFF OFF
OFF OFF OFF
ON OFF OFF
ON ON OFF
ON OFF OFF
ON ON OFF
ON OFF OFF
ON ON OFF
ON OFF OFF
OFF OFF OFF
OFF ON OFF
OFF OFF OFF
OFF ON OFF
OFF OFF OFF
OFF OFF OFF
OFF ON OFF
OFF ON OFF