Mitsubishi Electric CITY MULTI PUHY-400YMF-C Service Handbook page 96

2) Bypass solenoid valves (SV1, SV4) [Both SV1 and SV4 are on (open)]
<Variable capacity unit>
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)
SV1
ON
ON for 4 minutes
ON
ON for 3 minutes
ON
ON during oil recovery operation after con-
tinuous low-frequency compressor opera-
tion.
Pd 2.70 MPa
Thermo. Thermo.
OFF ON
(2-minute)
OFF
—
TH2 < – 30˚C
Pd
2.35 MPa Pd
and
after 30 seconds
ON when the high
pressure (Pd) ex-
—
ceeds the control
pressure limit.
• Td > 130˚C
and
• Pd > 1.96 MPa
—
or
TH2 < – 10˚ C
Defrost
(4-minute)
-93-
SV4
ON OFF
—
—
—
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)