Refrigerant Bypass Control - Mitsubishi Electric PUHY-M200YNW-A1 Service Handbook

[5-2 Outdoor Unit Control ]
5-2-4

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), (SV2) (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
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
During defrost
When returning to normal operation after
completion of the defrost cycle
At startup
Others
Operation
When high pressure (63HS1) rises during
the heating operation
During defrost
Others
12
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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
ON for 5 minutes
When TH7<= -20, SV2 stays on for
5 minutes after startup or until the
condition 63HS < 1.96 MPa (284
psi) is met
ON
When 63HS1 exceeds 3.50MPa
[507psi]
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 3.43MPa [497 psi]
or below in 30 seconds
SV2
OFF
Always ON
After 5 minutes have passed
Other than on the left
Always OFF
SV9
OFF
When 63HS1 is or below 2.70Mpa
[391psi]
Always ON
Always OFF
BS_05_E