Mitsubishi Electric City Multi CMH-WM250V-A, Service Handbook

Page: 131 / 436

[5-2 Outdoor Unit Control ]
12
- chapter 5 BS_05_E
5
Cont
rol
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
SV1a
ON OFF
When starting-up the compressor of each
outdoor unit
ON for 4 minutes.
After the restoration of thermo or 3 minutes
after restart
ON for 4 minutes.
During cooling or heating operation with the
compressor stopped
Always ON.
Exception: OFF when 63HS1-63LS is 0.2 MPa [29 psi] or less
After the operation has stopped ON for 3 minutes.
Exception: OFF when 63HS1-63LS is 0.2 MPa [29 psi] or less
During defrost operation ON
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)
When low pressure (63LS) drops
below 0.23 MPa [33 psi].
When low pressure (63LS) ex-
ceeds 0.38 MPa [55 psi].
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 the low pressure (63LS)
drops below 0.12 MPa [17 psi]
When the low pressure (63LS) ris-
es above 0.16 MPa [23 psi]
When high pressure (63HS1) rises When 63HS1 exceeds
3.62 MPa [525 psi]
When 63HS1 is 3.43MPa [497 psi]
or below in 30 seconds
Operation
SV2
ON OFF
During defrost Always ON
When returning to normal operation after
completion of the defrost cycle
ON for 5 minutes After 5 minutes have passed
At startup When TH7<= -20, SV2 stays on for
5 minutes after startup or until the
condition 63HS < 1.96 MPa (284
psi) is met
Other than on the left
Others Always OFF
Operation
SV9
ON OFF
When high pressure (63HS1) rises during
the heating operation
When 63HS1 exceeds 3.50MPa
[507psi]
When 63HS1 is or below 2.70Mpa
[391psi]
During defrost Always ON
Others Always OFF
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