Toshiba MMU-P0121H Service Manual page 34

Item
8. Release valve (1) SV2 gas balance control
control
This control is executed to balance the gas when opening SV2
while the compressor is off, in order to decrease the activation
load in the next compressor-ON time. This control is individually
executed by the master outdoor unit and each server outdoor unit.
1) Control conditions
2) Contents of control
Pd pressure
control point
In case of master
In case of terminal
(2) SV2 high pressure release control
This control is to control pressure rising in low-frequency operation
of the inverter.
1) Control conditions
2) Contents of control
3) Stop conditions
(3) SV2 low pressure release control
This control is to prevent quick pressure lowering in transient
operation. This control is individually executed by the master
outdoor unit and each server outdoor unit.
This control is executed as necessary except during stop time and
thermostat-OFF time.
1) Contents of control
(4) SV2 compressor case bypass control
This control is to prevent oil dilution up or 2-layers separation
status in transient operation. This control is individually executed
by the master outdoor unit and each server outdoor unit.
This control is executed during compressor-ON (except during oil
level detection controlling).
Operation explanation and applied data, etc.
When the compressor is switched from ON to OFF operation.
• The control point is exchanged by △P (Pd pressure - Ps
pressure) immediately before compressor stop.
• When △P ≥ P1, SV2 is opened. After SV2 has been opened,
SV2 is turned off when △P < P2.
• When △P < P1, SV2 is closed.
Heating
Master outdoor
compressor OFF
P1, P2
P1 P2
1.3 1.1
1.3 1.1
• Heating operation is performed.
(Except while defrost control is performed.)
• When No.1 compressor of the master outdoor unit only is
singly operated. (When 42Hz or lower command is output in
case of inverter unit.)
• SV2 is turned on when Pd pressure ≥ 2.7MPa.
• SV2 is turned off when Pd pressure ≤ 2.05MPa.
• In stop time, thermostat OFF, defrost operation, or cooling
operation.
• When No.2 compressor of the master outdoor unit is ON.
• When even one of the terminal compressors is ON.
• When the inverter frequency command becomes 51Hz or
higher.
• SV2 is opened when Ps pressure ≤ 0.08 MPa
• SV2 is closed when Ps pressure > 0.12 MPa
Cooling
Master outdoor Master outdoor
compressor OFF compressor ON
P1 P2 P1
1.3 1.1 —
1.3 1.1 0.5
3-31
Remarks
(MPa)
P2
—
0.4