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67
No.
8
9
Item
Release valve
control
Frequency
release
control
Operation explanation and applied data, etc.
(1) SV2 gas balance control
In order to decrease the starting load on the compressor, SV2 valve
is opened during the time the compressor is ‘OFF’, and the gas is
balanced.
(2) SV2 high pressure release control
This function limits the pressure level during the low frequency
operation of the inverter.
(3) SV2 low pressure release control
This function is used to prevent rapid pressure drop during transient
operation of the unit. This is performed by the header unit only. The
function is performed when required, except during ‘No demand’
status or when the system is in ‘Standby’.
(4) SV41, SV42 valves
1) SV41, 42 low-pressure release control
This function is used to prevent pressure dropping to low.
The function is performed during defrost operation, heat start up,
all cooling operation, or mainly cooling or part heating operation.
• Control contents (Defrost/heating start pattern)
Turn on SV41 and SV42 when PS pressure ≤ 0.1MPa, and turn
off SV41 and SV42 when PS pressure ≥ 0.15MPa.
• Control contents (All cooling operation, Mainly cooling, part
heating operation)
Turn on SV41 and SV42 when PS pressure ≤ 0.14MPa and Pd
pressure ≤ 1.8MPa, and turn off SV41 and SV42 when PS
pressure ≥ 0.24MPa and Pd pressure ≥ 2.2MPa
2) High pressure release control
This function is for gas bypass control which emergently prevents
the high pressure cut.
Turn on SV41 and SV42 when Pd pressure ≥ 3.5MPa, and turn off
SV41 and SV42 when Pd pressure ≤ 3.45MPa.
(5) SV6 valve
1) Cooling bypass control
This function is a liquid refrigerant bypass control to suppress the
rise of the discharge temperature or the inside temperature of the
compressor.
Turn on SV6 valve when the discharge temperature (TD1 or TD2)
becomes 96°C or higher and turns off when it drops below 84°C
by bypassing liquid refrigerant.
(6) PMV3
1) High pressure release control (All heating operation)
This function suppresses the rise of high pressure during the
inverter low frequency operation when in all heating operation
mode.
Set up PMV3 opening to 45 pulses when Pd pressure = 3.45MPa.
2) High pressure release control (All cooling operation)
Set up PMV3 opening to 60 pulses when Pd pressure = 3.5MPa.
(1) High pressure release control
This function is to correct the operation command of the compressor
and suppress the rise of high pressure.
1) Control contents
The operation frequency is decreased by 1 step when Pd pres-
sure ≥ 3.4MPa. It is decreased by 1 step every 10 seconds until
Pd pressure drops below 3.4MPa.
2) Release condition
• When Pd pressure ≤ 3.2MPa
• When refrigerant recovery control starts in all heating mode
• During defrost operation, stop, thermo OFF
Remarks