Heat Exchanger Mode Control - Hitachi FSXN Series Service Manual

5 Control system

5.1.3 Heat exchanger mode control

• Heat recovery system: in accordance with the connected load of indoor units, the outdoor unit heat exchanger can
switch as indicated in the following table.
• Heat pump system: in accordance with the operation mode of the indoor units, the outdoor unit heat exchanger can
switch as indicated in the following table.
N O T E
Outdoor unit heat exchanger mode at cooling: condenser (COND).
Outdoor unit heat exchanger mode at heating: evaporator (EVAP).
1 Heat exchanger mode:
• COND: operating as condenser.
• cond: avoid using the heat exchanger (under high pressure conditions).
• EVAP: operating as evaporator.
• evap: avoid using the heat exchanger (under low pressure conditions).
2 Expansion valve control method:
• Pd: normally, completely open (the opening depends on the refrigerant cycle conditions). PI control is
carried out to reach the discharge pressure objective value when it decreases.
• TdSH: PI control is carried out to reach the compressor TdSH objective value.
• Heat exchanger SH: PI control is carried out to reach the heat exchanger SH objective value.
The number of outdoor unit: 1
Heat exchanger mode
Heat exchanger condition
RVR2
Reversing valve
RVR1
MV1
Expansion valve
MVB
The number of outdoor unit: 2
Heat exchanger mode
Heat exchanger condition
Reversing valve
Main outdoor
unit
Expansion valve
Heat exchanger condition
Reversing valve
Secondary
outdoor unit
Expansion valve
94
SMGB0065 rev. 1 - 12/2010
Cooling mode Mainly cooling mode
COND D1
COND COND
OFF OFF
ON OFF
Pd
TdSH TdSH
Cooling mode Mainly cooling mode
COND D1
COND COND
RVR2 OFF OFF
RVR1 ON OFF
MV1 Pd
MVB TdSH
COND COND
RVR2 OFF OFF
RVR1 ON OFF
MV1 Pd Pd
MVB TdSH
Mainly heating mode
D1-1 D4
cond EVAP
OFF ON
OFF OFF
Pd Heat exchanger SH
Ps protection
Mainly heating mode
D2 D3 D4
COND cond EVAP
OFF OFF ON
OFF OFF OFF
Pd Heat exchanger SH
TdSH
evap EVAP EVAP
ON ON ON
OFF OFF OFF
Completely closed
TdSH
Heating mode Defrost mode
EVAP DEF1
EVAP COND
ON OFF
OFF ON
Completely open
TdSH
Heating mode Defrost mode
DEF2
EVAP
With CH unit Without CH unit
EVAP COND/EVAP
ON ON/OFF
OFF OFF
Completely
Completely
open/Heat
exchanger SH
EVAP COND/EVAP
ON ON/OFF
OFF OFF
Completely
Completely
open/Heat
exchanger SH
DEF1
COND
OFF
ON
closed
COND
OFF
ON
closed