Item Description of operation, numerical data, and other information Remarks
8. Release
valve control
(1) SV4 gas balance control
This control turns on SV4 when the compressor is stopped to balance the gas and
reduce the starting load when the compressor is turned on next time. This control is
performed independently by the center unit and each terminal unit.


Control condition
• At power on
• When the compressor is switched from ON to OFF during cooling operation or
heating operation.


Control content
• SV4 (x) is turned on when the power is turned on, and then turned off when ΔP
(= Pd - Ps) becomes 2.0 or less.
• SV4 (x) turns on when the compressor turns off.
(Turns on when ΔP (Pd - Ps) is 3.0 or more, and turns off
when ΔP (Pd - Ps) is 2.0 or less.)
(2) SV4 high pressure release control
This control is a control to suppress the high pressure rise during cooling operation and
heating operation. This control is performed independently by the header unit and each
follower unit.


Control condition
• Compressor ON


Control content
• When Pd ≥ P1, SV4 (x) is turned on.
• When Pd ≤ P2, SV4 (x) is turned off.
* P1 and P2 of each outdoor unit are as follows
Pd control
point
Heating
Cooling


Release condition
• When the system is stopped and the thermostat is off
(3)
SV4 low pressure release control
• The purpose of this control is to protect the Ps drop during compression ON.
• This control is performed independently by the header unit and each follower unit.


Control condition
The outdoor unit that is turned on will judge each item individually.


Control content
• When Ps ≤ 0.16, turn on SV4 (x).
• When Ps ≥ 0.20, SV4 (x) is turned off.


Release condition
• When the system is stopped and the thermostat is off
P1
P2
3.38MPa
3.33MPa
3.70MPa
3.68MPa
3.70MPa
3.68MPa
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