Mitsubishi Electric PUHY-P72 Service Manual page 106

[ VII Control ]
-5- Bypass Control
Bypass solenoid valves (SV1a), which bypass the high- and low- pressure sides, perform the following functions.
(1) Bypass solenoid valve (SV1a) (ON = Open), (SV9) (ON = Open)
Operation
When starting-up the compressor of each
outdoor unit
After the restoration of thermo or 3 minutes
after restart
During cooling or heating operation with the
compressor stopped
After the operation has stopped
During defrost operation
While the compressor is operating at the
minimum frequency and when the low pres-
sure (63LS) drops (3 or more minutes after
compressor startup)
When high pressure (63HS1) rises
Operation
When high pressure (63HS1) rises during
the heating operation
When startup or resuming operation after a
defrost cycle
Others
HWE0804A
ON
ON for 4 minutes.
ON for 4 minutes.
Exception: OFF when 63HS1-63LS is 0.2 MPa [29 psi] or less
ON for 3 minutes.
Exception: OFF when 63HS1-63LS is 0.2 MPa [29 psi] or less
When low pressure (63LS) drops
below 0.23 MPa [33 psi].
When 63HS1 exceeds
3.62 MPa [525 psi]
ON
When 63HS1 exceeds 3.50MPa
[507psi]
ON for 5 minutes and goes OFF
- 97 -
SV1a
OFF
Always ON.
ON
When low pressure (63LS) ex-
ceeds 0.38 MPa [55 psi].
When 63HS1 is or below
3.43 MPa [497 psi] and 30 seconds
have passed
SV9
OFF
When 63HS1 is or below 2.70Mpa
[391psi]
Always OFF
GB