Hitachi RAS-8FSXN - 5 Control System; Cycle Control

5.1 Control system
5.1.1 Cycle control
Control device
Cooling
Heating
Heat recovery
Defrost
Purpose Contents Purpose Contents Contents
Compressor
Inverter frequency
Total operation
capacity of the
indoor unit
Capacity control is
carried out
to reach
the evaporation
temperature
objective value
Total operation
capacity of the
indoor unit
PI control is carried
out to reach the
Pd objective value.
All the
compressors
operating
Electronic
expansion valve
for
the outdoor unit
heat exchanger.
Capacity control
Completely open
(the opening of the
electronic
expansion valve is
dependent on the
refrigerant cycle
conditions)
Condenser COND
Capacity control
Condenser COND
Completely open
(the opening of the
electronic
expansion valve is
dependent on the
refrigerant cycle
conditions)
Completely
open
Evaporator EVAP
outdoor unit heat
exchanger SH
Evaporator
EVAP PI control is
carried out to reach
the superheat
objective value in
the outdoor unit
heat exchanger.
Electronic
expansion valve
for
the supercooling
heat exchanger.
TdSH control
Control TdSH of
the compressor to
reach the objective
value
TdSH control
Control TdSH of
the compressor to
reach the objective
value
TdSH control
Electronic
expansion valve
for
the indoor unit heat
exchanger
Indoor unit heat
exchanger SH
PI control is carried
out to reach
objective value in
the
indoor unit heat
exchanger SH
<Cooling setting>
Indoor unit heat
exchanger SH
<Cooling
setting> PI control
is carried out to
reach the objective
value in the indoor
unit heat
exchanger SH
Indoor unit
heat
exchanger
SH
<Heating setting>
Indoor unit heat
exchanger SH
<Heating setting>
Control SC of the
indoor unit liquid
thermistor to reach
objective value
Outdoor unit fan Pd control
PI control is carried
out to reach the
Pd objective value
Condenser
COND
Pd control
Condenser
COND
PI control is
carried out to reach
the Pd objective
value
Stoppage
Evaporator EVAP
Fixing by ambient
temperature and
operating capacity
Evaporator EVAP
Fan rotation is
controlled by the
ambient
temperature and
the indoor unit
operating capacity
Gas bypass valve
(SVA)
1. Increase in Pd
protection
2. Decrease in Pd
protection
1. Pd > 3.6 MPa:
ON
2. Ps < 0.15 MPa:
ON
1. Increase in Pd
protection
2. Decrease in Pd
protection
1. Pd > 3.6 MPa:
ON
2. Ps < 0.15 MPa:
ON
Closed
5 Control system
88
SMGB0065 rev. 1 - 12/2010