Sv41, 42 Low Pressure Release Control; Sv52 High Pressure Release Control - Toshiba MMY-MAP0806HT8P Service Manual

Item Description of operation, numerical data, and other information
9. Release

4. SV41, 42 low pressure release control

valve control This control function is aimed at providing low pressure protection, and is individually
(cont'd) performed by the header unit and each follower unit.
The control takes place during defrost operation, heating startup pattern control
operation, and cooling operation.
1) Control details (heating)
When Ps pressure becomes
pressure becomes
2) Control details (cooling)
When Ps pressure and Pd pressure become
respectively, SV41 and 42 are opened; when Ps pressure and Pd pressure
become

5. SV52 high pressure release control

This control function is aimed at mitigating pressure rise and is only performed by the
header unit.
1) Control details (heating)
When Pd pressure and compressor speed become
respectively, during heating, with a single compressor in operation, SV52 is
opened; when Pd pressure becomes
SV52 is closed.
10. High
This control function is aimed at automatically shutting down a compressor in an
pressure outdoor unit depending on Pd pressure. It is individually performed by the header unit
release and each follower unit.
compressor 1) Control details
• Compressors are shut down when Pd pressure reaches or exceeds P01 and P02.
shutdown
• The compressor restart prevention timer (2 minutes 30 seconds) is set, and the control
control
terminated.
11. Case There are two types of case heaters: a compressor case heater and an accumulator
heater case heater. This control function is aimed at preventing the accumulation of refrigerant
control in those cases, and is performed by all outdoor units.
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
turned back on when T0 sensor temperature becomes
• When the compressors are turned on, the heaters are kept on for 10 minutes.
0.1 MPa, SV41, 42 are opened; when Ps
0.15 MPa, SV41, 42 are closed.
0.19 MPa and 2.2 MPa, respectively, SV41 and 42 are closed.
0.14 MPa and 1.8 MPa,
3.4 MPa and
2.7 MPa, or compressor speed
28 °C, and are
25 °C.
− 74 −
Remarks
38 rps,
64 rps,
• When Pd P01 compressor
No. 2 (the last one of two
compressors in terms of
startup order in a two
compressor configuration) is
shut down.
• When Pd P02 compressor
No. 1 (the first compressor
in terms of startup order) is
shut down.
P01
Heating 3.45
Cooling 3.85
(unit : MPa)
P02
3.5
3.9