Heat Recovery Operation Control; Operation Mode Selection And Controlling; Ompressor Operation; Operation / Stop Condition - Fujitsu Airstage VR-II Series Service Manual

2-3 Heat Recovery Operation controlling

2-3-1 Operation mode selection and controlling

Under Heat Recovery operation, the heat balance for the system is controlled based on the Target High pressure and the Target low pressure.
By changing compressor rotation speed or changing Heat exchange capacity, the system can maintain the good heat balance.
The target High pressure value and the target low pressure value in the target range are decided by the outdoor unit's operation mode (Cond-
ensor or Evaporator).
The outdoor unit's operation mode is decided by depending on the operation order from the connecting indoor unit at the first start up.
- Indoor unit's cooling demand is bigger than heating demand: Outdoor unit operates as Condensor
- Indoor unit's heating demand is bigger than cooling demand: Outdoor unit operates as Evaporator
After the mode was decided at the start up, the operation mode of outdoor unit will be selected by based on the target pressure.
P
Target: LP
Ex. When the refrigerant flow is required
HP
P
Target: LP
Ex. When the refrigerant evaporation is required
2-4 COMPRESSOR OPERATION

2-4-1 Operation / Stop Condition

When cooling requirement capacity or heating requirement capacity from either of the indoor units in the same
refrigerant circuit is input, the compressor operates.
When all the indoor units in no "cooling requirement capacity" or "heating requirement capacity", the compressor
is stopped.
But in the following case, the compressor operates in accordance with operation of each mode.
During 3 minute restart prevention operation
Icing protection
Failure (Refer to chapter 4, TROUBLE SHOOTING )
Oil recovery
Under expansion valve initialization
At protective operation
Emergency stop
Defrost operation
Peak cut stop operation
Target: HP
Compressor rps UP
H
Target: HP
Condensor capacity: DOWN)
(Evaporator capacity: UP)
H
LP
P
Condensor capacity: UP
(Evaporator capacity: DOWN)
Ex. When the refrigerant condensation is required
Targeted
(HP & LP)
P
Compressor rps DOWN
Ex. When the refrigerant flow is not required
LP
02-03
Target: HP
Target: LP
H
HP
Target: HP
Target: LP
H