Mitsubishi Electric CITY MULTI PUHY-400YMF-B Service Handbook page 73

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 %
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 for 3 minutes
ON during oil recovery operation af-
ter continuous low-frequency com-
pressor operation.
Pd 27.5 kg/cm 2 G
(2.70 MPa)
Thermo. Thermo.
OFF ON
(2-minute)
SV22 SV32
Coil Valve Coil Valve
OFF Open OFF Closed
ON Closed ON Open
OFF
ON
ON
—
TH2 < – 30°C
Pd 24 kg/cm 2 G
Pd
(2.35 MPa) and
after 30 seconds.
ON when the high pres-
—
sure (Pd) exceeds the
control pressure limit.
• Td > 130°C
and
—
• Pd > 20 kg/cm
or
TH2 < – 10°C
Defrost
(4-minute)
–70–
SV4
ON
—
—
—
Normally ON
—
TH2 – 15°C.
2
23 kg/cm G Pd 23 kg/cm
(2.26 MPa)
(2.26 MPa) and after
30 seconds
Pd 20 kg/cm
(1.96 MPa)
Td 115°C
2 G
(1.96 MPa)
Stop
(3-minute)
SV22
SV32
COMP
OFF
2 G
2 G