Various Protections - Fujitsu ASU18RMLQ Service Instruction

23. VARIOUS PROTECTIONS

(1). DISCHARGE GAS TEMPERATURE OVERRISE PREVENSION CONTROL
The discharge gas thermosensor (discharge thermistor : Outdoor side) will detect discharge gas
temperature.
When the discharge temperature becomes higher than Temperature ,the compressor frequency
is decreased 20 Hz, and it continues to decrease the frequency for 20 Hz every 120 seconds until
the temperature becomes lower than Temperature .
When the discharge temperature becomes lower than Temperature ,the control of the control of the
compressor frequency is released.
When the discharge temperature becomes higher than Temperature
and the indoor unit LED starts blinking.
(Table 11 : Discharge Temperature Over Rise Prevension Control / Release Temperature)
AOU24/36RML
(2). CURRENT RELEASE CONTROL
The compressor frequency is controlled so that the outdoor unit input current does not exceeds
the current limit value that was set up with the outdoor temperature.
The compressor frequency returns to the designated frequency of the indoor unit at the time
when the frequency becomes lower than the release value.
(3). ANTI-FREEZING CONTROL (Cooling mode)
The compressor frequency decreases on cooling mode when the indoor heat exchanger
temperature sensor detects the temperature lower than 37.4°F (3°C).
Then, the anti-freezing control is released when it becomes higher than 42.8°F (6°C).
(Fig 7 : Anti-freezing Protection Operation / Release Temperature)
Indoor heat exchange
temperature
37.4°F
(3°C)
42.8°F
(6°C)
46.4°F
(8°C)
(4). COOLING PRESSURE OVER RISE PROTECTION
When the outdoor unit heat exchange sensor temperature rises to
the compressor is stopped and error display is indicated.
Temperature
Temperature
230°F(110°C) 212°F(100°C)
The compressor frequency is
decreased 10Hz every 120 seconds.
Hold
Compressor OFF : Hold
Compressor ON : Release of protection
Release of protection
01-21
,the compressor is stopped
Temperature
239°F(115°C)
158.9°F (70.5°C)
or greater,