Mitsubishi Electric CITY MULTI PUHY-400YMF-C Service Handbook page 70

2) Bypass solenoid valves (SV1, SV4) [Both SV1 and SV4 are on (open)]
Item
At compressor is started
Compressor stopped during cool-
ing or heating mode
After operation has been stopped
During defrosting ((*1) in Fig below)
During oil recovery operation
When low pressure saturation
temperature (TH2) has dropped
during lower limit frequency opera-
tion(15 minutes after start)
When the high pressure (Pd) is
risen up during lower limit fre-
quency operation (3 minutes after
starting)
When the discharge temperature
(Td) is risen up
* Example of operation of SV1
Compressor
Bypass
solenoid
Start
valve (SV1)
(4-minute)
3) Capacity control solenoid valve (SV22, SV32) *Model 500 only.
• Operation of solenoid valve
Solenoid valve
Status
Full-load
(Operating at 100 %
OFF
capacity)
Un-load
(Capacity control
operation)
• SV22 and SV32 stand for SV2 and SV3 of the No. 2
compressor.
SV1
ON
ON for 4 minutes
ON
ON for 3 minutes
ON
ON during oil recovery operation af-
ter continuous low-frequency com-
pressor operation.
Pd 2.70 MPa
Thermo. Thermo.
OFF ON
(2-minute)
SV22 SV32
Coil Valve Coil Valve
Open OFF Closed
ON Closed ON Open
OFF
—
TH2 < – 30˚C
Pd 2.35 MPa and
Pd
after 30 seconds.
ON when the high pres-
—
sure (Pd) exceeds the
control pressure limit.
• Td > 130˚C
and
—
• Pd > 1.96 MPa
or
TH2 < – 10˚C
Defrost
(4-minute)
-67-
SV4
ON
—
—
—
Normally ON
—
TH2 – 15˚C
2.26 MPa Pd
2.26 MPa and
after 30 seconds
1.96 MPa
Pd
Td 115˚C
Stop
(3-minute)
SV22
SV32
COMP
OFF