Mitsubishi Electric PUHY-HP144TSHMU-A Service Handbook page 93

[ VII Control ]
-5- Bypass Control
Solenoid valves are categorized into 3 types: High/low pressure bypass valve (SV1a), High/low pressure bypass valve via
heat exchanger (SV9), and circuit switch valve at subcool coil low pressure side (SV6). Refer to the following tables for each
valve operation.
(1) Bypass solenoid valve (SV1a) (ON = Open)
Operation
At NO1 compressor startup (outdoor tem-
perature: -15°C[5°F] or more) or at NO2
compressor startup (HP144/HP192 models)
After resuming operation after the comple-
tion of the defrost cycle
After NO1 compressor startup (outdoor tem-
perature: -15°C[5°F] or lower) or after re-
suming operation after the completion of the
defrost cycle (outdoor temperature:
-15°C[5°F] or lower)
After resuming operation after Themo mode
or after 3-minute restart delay mode
When the compressor stops at cooling/heat-
ing mode
After the operation has stopped
During defrost cycle
During oil recovery operation
During cooling operation, during compres-
sor frequency Fmin operation, or when low
pressure (63LS) drops (3 minutes have
passed since startup)
During heating operation and when low
pressure (63LS) drops (3 minutes have
passed since start up and resuming opera-
tion after the completion of the defrost cycle
.)
When high pressure (63HS1 or 2) rises
(2) Bypass solenoid valve (SV2) (ON = Closed)
Operation
At NO1 compressor startup (outdoor tem-
perature: 5°C[41°F] or lower) or after resum-
ing operation after the completion of the
defrost cycle
HWE0716A
ON
ON for 4 minutes.
ON for 8 minutes.
ON when 25 minutes or less have
passed and 63HS1 or 2 < 1.96MPa
[284 psi].
ON for 4 minutes.
Exception: OFF when 63HS1 or 2 -63LS is 0.2 MPa [29 psi] or less
ON for 3 minutes.
Exception: OFF when 63HS1 or 2 -63LS is 0.2 MPa [29 psi] or less
OFF during oil recovery operation (cooling/heating) after low frequency
continuous operation.
When low pressure (63LS) drops
below 0.23 MPa [33 psi].
When low pressure (63LS) drops
below 0.12 MPa [17 psi].
When 63HS1, 63HS2 exceeds
3.62 MPa [525 psi].
ON
ON when 5 minutes or less have
passed and 63HS1 < 1.96MPa
[284 psi].
- 84 -
SV1a
OFF
OFF when 25 minutes or more
have passed or 63HS1 or 2
1.96MPa [284 psi].
Always ON.
ON
When low pressure (63LS) rises
above 0.38MPa [55 psi].
3 minutes have passed since ON
control started, and when low pres-
sure (63LS) drops below 0.16MPa
[23 psi].
When 63HS1, 62HS2 are or below
3.43 MPa [497 psi] and 30 seconds
have passed.
SV2
OFF
OFF when 5 minutes or more have
passed or 63HS1 1.96MPa [284
psi].
GB