9
. Release
valve control
(cont’d)
4.
SV41, 42
low pressure release control
This control function is aimed at providing low pressure protection.
The control takes place during defrost operation, heating startup pattern control
operation, and cooling operation.
1)
Control details (heating)
When P
S
pressure becomes 0.1 MPa, SV41, 42 are opened; when P
S
pressure becomes 0.15 MPa, SV41, 42 are closed.
2) Control details (cooling)
When P
S
pressure and P
D
pressure become 0.14 MPa and 1.
7
MPa,
respectively, SV41 and 42 are opened; when P
S
pressure and P
D
pressure
become 0.
22
MPa and
1.9
MPa, respectively, SV41 and 42 are closed.
5.
SV5
2
high pressure release control
This control function is aimed at mitigating pressure rise.
1)
Control details (heating)
When P
D
pressure and compressor speed become 3.4 MPa and 38 rps,
64 rps,
respectively, during heating, with a single compressor in operation, SV5
2
is
opened; when P
D
pressure becomes 2.7 MPa, or compressor speed
SV5
2
is
closed.
10
. High
pressure
release
compressor
shut
down
control
This control function is aimed at automatically shutting down a compressor in an
outdoor unit depending on P
D
pressure.
1)
Control details
• Compressors are shut down when P
D
pressure reaches or exceeds P0
1 and P02
.
• The compressor restart prevention timer (2 minutes 30 seconds) is set, and the control
terminated.
• When P
D
P
01
compressor
No. 2
(the last
one of
two
compressors in
terms of
startup order in a
two
compressor configuration) is
shut down.
•
1
1
. Case
heater
control
There are two types of case heaters: a compressor case heater and an accumulator
case heater. This control function is aimed at preventing the accumulation of
refrigerant in those cases.
If the power supply has not been turned on for a specified period before a post-
installation test run, compressor failure may occur. Similarly, when starting
compressors after a long period of no power supply, it is recommended that the power
supply be turned on for a while before operation is resumed, just like a post-installation
test run.
This control function is sometimes used alongside an electrical charging of the
compressor motor windings. In this case, a charging sound may be heard, but this is
normal.
1) Control details
• The heaters are turned on while the compressors are turned off.
• The heaters are turned off when T0 sensor temperature becomes
28 °C, and are
turned back on when T0 sensor temperature becomes 25 °C.
• When the compressors are turned on, the heaters are kept on for 10 minutes.
Item
Description of operation, numerical data, and other information
Remarks
When P
D
P
0
2
compressor
No.
1
(the
first
compressor
in
terms of
startup order
)
i
s
shut down.
P01
P02
Heating
3.
6
3.5
Cooling
3.85
3.
8
(unit : MPa)
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