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8-2. Protection Function Summary
• Protection Controls varies by Outdoor unit, please see appropriate Outdoor unit service manual for full details
(Below "Protection Function Summary" is according to SMMS-u.)
Function
Freeze prevention control
(Low temperature release)
Cooling oil (refrigerant)
recovery control
Heating refrigerant (oil)
recovery control
(Heating Start up Control)
Defrost control
(Full Defrost)
High Pressure release
control
Case Heater control
In Cooling Mode prevents low DX-COIL temperatures by controlling compressor speed
(based on TC1/TC2/TCJ sensor temperature).
This control periodically increases flow-rate to ensure refrigerant oil does not build up
in inter-unit gas pipes (which can occur when operating command is inadequate, or while
cooling is progressed under low ambient conditions).
During this control the compressors are operated at a target speed, and Dx valve kit
PMV is opened to a certain degree. Upon completion of recovery control normal Cooling
operation resumes.
This control periodically increases flow-rate to ensure liquid refrigerant trapped inside
the DX COIL. It also serves the purpose of recovering DX COIL / Outdoor refrigerant after
defrosting and recovering oil present in outdoor heat exchangers during heating overload
operation.
During this control the compressors are operated at a target speed, and Dx valve kit
PMV is opened to a certain degree. Upon completion of recovery control normal Heating
operation resumes. Recovery operation normally takes place after defrosting.
In Heating mode a defrost operation can be performed to reduce ice build-up on the
Outdoor unit (based on TE1 & TE2, TE3 sensor). During Defrosting the refrigerant cycle is
reversed temporarily cooling the DX COIL.
During the heating operation, if the TE sensor detected temperature falls below the predicted
TE sensor temperature by a specified amount, or if the TE sensor detected temperature falls
below the frosting temperature for 300 minutes, the defrosting operation starts.
(After start-up or when switching from cooling to heating, frost judgment is performed and the
defrosting operation is started according to the judgment result.)
While the outdoor unit is Defrosting the Dx valve kit PMV is opened to a certain degree.
Heating Recovery operation normally takes place after defrosting.
* In the case of the coupled system, when any of the outdoor units satisfies the defrosting
start condition, all the units in the group to which the unit belongs start defrosting operation,
and the other Gr units continue heating operation.
This control function is aimed at automatically shutting down a compressor in an outdoor unit
depending on Pd. It is individuality performed by the header unit and each follower unit.
• Compressors are shut down when Pd reaches or exceeds P0
• The Pd control point P0 is switched according to the start priority of the outdoor unit
• The compressor restart prevention timer (2 minutes 30 seconds) is set, and the
controlterminated.
Pd control point P0
Outdoor unit
priority1
Except outdoor unit
priority1
There are 1 types of case heater: a compressor case heater.
This control function is aimed at preventing the accumulation of refrigerant in those case,
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.
Summary
Cooling
compressor1
548 PST
compressor2
540 PST
compressor1
540 PST
compressor2
540 PST
– 39 –
Heating
512 PST
506 PST
500 PST
595 PST
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