Hitachi RAS-25QH1 Technische Information Seite 183

11. Temperature Detector Circuit
(1) Pipe thermistor, overheat (OH) thermistor, FIN thermistor, defrost (DEF) thermistor, outdoor temperature thermistor
6 | Multiplexer switching
»! Outdoor Microcomputer
(AX-8H20)
e@ The pipe thermistors detect the temperatures of the pipes connected to each indoor unit.
@ The OH thermistor detects the temperature of the compressor.
@ The temperature detection data from the pipe and OH thermistors is input to the outdoor microprocessor
as data which determines the opening of expansion valves.
@ The OH thermistor also detects overheating of the compressor. When the temperature data of OH
thermistor reaches the operation value, the compressor stops.
e@ The FIN thermistor detects the temperature of the radiating fin for the power module. The temperature
data of FIN thermistor is supplied to pin © of the outdoor microcomputer through IC1 pin (3. When it
reaches the operation value, the compressor stops.
@ The DEF thermistor detects the temperature of the outdoor heat exchanger. The detected temperature
is supplied to pin 68 of the outdoor microcomputer through IC1 pin @, and is used to judge whether
defrosting should be activated or not.
.
e@ The outdoor temperature thermistor detects outdoor temperature and supplies the data to pin @ of the
outdoor microcomputer through IC1 pin @3. The outdoor micro computer adds the outdoor temperature
data to the operation command from the indoor unit to calculate the optimum operating condition and
controls the compressor rotation speed.
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