28
6. Release
valve control
Item
Description of operation, numerical data, and other information
Remarks
1. SV2 gas balance control
This control function is aimed at achieving gas balance by opening SV2 while
compressors are turned off so as to reduce their startup load the next time they
are turned on.
1) Control conditions
The compressors have been turned off.
2) Control details
The control point is changed according to
ǻ
P (Pd pressure - Ps pressure)
registered just before the compressors were turned off.
When
ǻ3
1.3MPa, SV2 is opened. When this results in
ǻ3
1.1MPa, SV2 is
closed.
When
ǻ3
1.3MPa, SV2 is closed.
2. SV2 high pressure release control
This control function is aimed at mitigating pressure rise while a compressor is in
operation at low speeds.
1) Control conditions
Heating operation is in progress (except periods of defrosting control).
A speed of the compressor is in operation at low speeds of up to 77 rps.
2) Control details
When Pd pressure becomes 3.4 MPa, SV2 is opened.
When Pd pressure becomes 2.8 MPa, SV2 is closed.
3) Termination conditions
Shutdown, thermo OFF, defrosting operation, or cooling operation.
The speed of the compressor rises to 82 rps or more.
3. SV2 low pressure release control
This control function is aimed at preventing a rapid fall in pressure during transient
operation.
The control is always provided except during periods of stoppage or thermo OFF.
1) Control details
When Ps pressure becomes 0.14 MPa, SV2 is opened.
When Ps pressure becomes 0.24 MPa, SV2 is closed.
4. SV4 low pressure release control
This control function is aimed at providing low pressure protection.
1) Control details (heating)
When Ps pressure becomes 0.1 MPa, SV4 is opened; when Ps pressure
becomes 0.2MPa, SV4 is closed.
2)
When Ps pressure and Pd pressure become 0.14 MPa and 1.8 MPa,
respectively, SV4 is opened; when Ps pressure and Pd pressure become
0.24 MPa and 2.2 MPa, respectively, SV4 is closed.
Control details (cooling)
25
