Mitsubishi Electric PURY-P72 Service Handbook page 154

[ VII Control ]
Bypass 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 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
(2) Bypass solenoid valve (SV9) (ON = Open)
Operation
When high pressure (63HS1) rises during
the heating operation
Others
(3) Bypass solenoid valve (SV5b) (ON = Closed)
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
HWE1116D
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 (Closed)
When the pressure is 2.70MPa
[391psi] or below
ON (Closed)
ON (Closed)
OFF (Open) for 5 minutes and goes ON (Closed)
Always ON (Closed)
- 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
SV5b
OFF (Open)
When SV9 is ON and the pressure
is 3.50MPa [507psi] or more
GB