Forced Cooling - Hitachi RAF-25NH4 Service Manual

ORCED COOLING
Units can be operated in a cooling cycle to collect refrigerant.
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The conditions for execution and operation status are as follows:
[Conditions for execution]
¥Forced cooling operation will be executed when the forced cooling switch is turned ON and there is no
record that all indoor units 1-4 have been operated. This system commands the main and sub
microcomputers to simultaneously execute forced cooling.
¥The main microcomputer monitors operation records of all indoor units 1-4.
The main microcomputer always monitors the operation status of indoor units. When it detects an
operated unit, it inhibits forced cooling.
¥Since the forced cooling switch is provided on the main microcomputer side, the main microcomputer
transfers the forced cooling command to the sub microcomputer via communication line between
outdoor microcomputers. When the sub microcomputer receives this request, it executes forced cooling.
[Operation status]
¥Outdoor fan: Fixed at B(Lo).
¥Compressor rotation speed: Fixed at 4000 min
¥Expansion valves, Reversing valve: Same as usual operation.
[Special remarks]
¥Thermostat turns OFF when outdoor failure occurs during forced cooling, but this is not counted.
¥If it cannot be detected that indoor units for sub microcomputer are being operated because of a delay in
communications and the indoor unit for main microcomputer starts forced cooling, the sub
microcomputer will continue operation and the main microcomputer will release forced cooling
immediately.
¥Since the compressor rotation speed is fixed at 4000 min
when the compressor starts will not be executed.
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during forced cooling, the steady speed control
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