Mitsubishi Electric PURY-P72TYJMU-A Service Handbook page 154

[ 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)
Operation
When each indoor unit compressor startup
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
(2) Bypass solenoid valve (SV9) (ON = Open)
Operation
When high pressure (63HS1) rises during
the heating operation
Others
(3) Bypass solenoid valve (SV2) (ON = Open)
Operation
When high pressure (63HS1) rises during
the heating operation
When startup or resuming operation after a
defrost cycle
During defrost cycle
Others
*P72, P96 only
(4) Bypass solenoid valve (SV5b) (ON = Open)
Operation
When high pressure (63HS1) rises during
the heating operation
At startup
During defrost cycle
When returning to normal operation after
completion of the defrost cycle
Others
*SV2 is present only on the P72 and P96 models.
HWE0913A
ON
ON for 4 minutes.
ON for 4 minutes.
Exception: OFF when 63HS1-63LS is 0.2MPa[29psi] or less
ON for 3 minutes.
Exception: OFF when 63HS1-63LS is 0.2MPa[29psi] or less
When low pressure (63LS) drops
below 0.23MPa[33psi].
When 63HS1 exceeds
3.62MPa[525psi]
ON
When 63HS1 exceeds 3.50MPa
[507psi]
Always OFF
ON
When SV5b is OFF and the pres-
sure is 3.50MPa[507psi]or below
Always OFF
ON
When SV2 is OFF and the pressure
is 2.70MPa[391psi]or below *
ON for 5 minutes and goes OFF
Always OFF
- 145 -
SV1a
OFF
Always ON.
ON
When low pressure (63LS) ex-
ceeds 0.38MPa[55psi].
When 63HS1 is or below
3.43MPa[497psi] and 30 seconds
have passed
SV9
OFF
When SV5b is ON and the pressure
is 2.70MPa[391psi]or below
SV2
OFF
When 63HS1 exceeds 2.70MPa
[391psi]
OFF
ON
SV5b
OFF
When SV9 is ON and the pressure
is 3.50MPa[507psi]or below
ON
ON (open)
GB