Bypass Control - Mitsubishi Electric PQHY-P72TYHMU-A Service Handbook

[ 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 the compressor on each heat source
unit starts up
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 = Close)
Operation
When high pressure (63HS1) rises during
the heating operation
Others
HWE09080
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]
OFF
When 63HS1 exceeds 3.50MPa
[507psi]
- 144 -
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
ON
When the pressure is
2.70MPa[391psi]or below
Always ON
GB