Refrigerant Bypass Control - Mitsubishi Electric R410A Service Handbook

[5-2 Outdoor Unit Control ]
5-2-5

Refrigerant 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), (SV2) (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
During compressor operation at Fmin fre-
quency in the cooling mode and when the
low pressure (63LS) drops (three or more
minutes after compressor startup)
The following conditions are met during the
heating mode: Compressor frequency after
power on is greater than 0.
The low pressure (63LS) drops (One or
more minutes after compressor startup if the
cumulative compressor operation time is
one hour or less; three or more minutes if
the cumulative compressor operation time is
one hour or more)
When high pressure (63HS1) rises
Operation
When high pressure (63HS1) rises during
the heating operation
When returning to normal operation after
completion of the defrost cycle
Others
Operation
During defrost
HWE14080
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 the low pressure (63LS)
drops below 0.12 MPa [17 psi]
When 63HS1 exceeds
3.62 MPa [525 psi]
ON
When 63HS1 exceeds 3.50MPa
[507psi]
If TH7>-15°C, stays ON for five minutes, then turns off
If TH7< = -15°C, stays ON for 25 minutes,
or stays ON until 63HS's reading is below 1.96 MPa [284 psi], then turns off
SV2
ON
During defrost only
- 95 -
SV1a
OFF
Always ON.
ON
When low pressure (63LS) ex-
ceeds 0.38 MPa [55 psi].
When the low pressure (63LS) ris-
es above 0.16 MPa [23 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
OFF
All other times except during defrost
GB