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2. Processes and functions
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2-4 Control Functions
Electronic control valve control
Opening of the electronic control valve is controlled so
that the appropriate operating conditions are maintained,
based on the signal from each sensor (discharge
temperature [TD], intake temperature [TS], outdoor heat
exchanger temperature [C1], and indoor heat exchanger
temperature [E1, E2]).
Discharge temperature release control
(1) This control lowers the operating frequency of the
compressor when electronic control valve control is
unable to maintain the appropriate operating
conditions because the discharge temperature fails
to decline or because there is a sudden increase in
the discharge temperature.
(2) If the discharge temperature exceeds 232°F, the
compressor is stopped and then restarted. (Error
count = 1)
(3) The error count is cleared when operation has
continued for 10 minutes after the compressor was
restarted.
(4) If (2) repeats 4 times without the error count being
cleared (error count = 4), alarm "P03" occurs.
Current release control
The compressor operating frequency is controlled so
that the current that is input to the inverter compressor
does not exceed the designated value (control value).
Outdoor unit fan control
1. Cooling fan control
(1) The outdoor unit fan minimum speed and maximum
speed are determined according to the outdoor air
temperature and the operating frequency. The
speed is controlled in stages between the minimum
speed and maximum speed, based on the outdoor
heat exchanger temperature (C2) at that time.
(2) For 60 seconds after start, the outdoor unit fan
operates at maximum speed, as determined by the
outdoor air temperature and operating frequency at
that time. Subsequently, the fan operates at low
speed until the outdoor heat exchanger temperature
(C2) rises.
(3) If the discharge temperature (TD) sensor is
abnormal or has become disconnected, the fan will
not operate and a protective device is activated.
2. Heating fan control
(1) The outdoor unit fan minimum speed and maximum
speed are determined according to the outdoor air
temperature and operating frequency. The speed is
controlled in stages between the minimum speed
and maximum speed, based on the outdoor heat
exchanger temperature (C1) at that time.
(2) If the outdoor heat exchanger temperature (C1) is
75°F or higher continuously for 5 minutes, fan
operation may stop (same conditions as when the
thermostat is OFF). In this case, the fan will restart
after 3 minutes.
(3) This control is not performed during the 3 minutes
after start, for 1 minute after defrost ends, and
while defrost is in progress.
Coil heating control
(1) This control applies current to the coil of the
stopped compressor to heat the compressor in
place of the crank case heater.
(2) When the discharge temperature (TD) is less than
77°F, the current application judgment is made
based on the outdoor air temperature (TO).
• Current application starts when the outdoor air
temperature drops to 59°F or below.
• Current application stops when the outdoor air
temperature rises above 64°F.
Control for prevention of short intermittent operation
In order to protect the compressor, this control does not
allow the compressor to be stopped for 10 minutes after
operation starts, even if the thermostat OFF signal is
received from the indoor unit.
Control for prevention of high cooling loads
This control reduces abnormal high-pressure increases
during cooling operation.
(1) If MAX (C1, C2) (C1 & C2: outdoor heat exchanger
temperature) is less than 124°F, the compressor
performs normal operation.
(2) If MAX (C1, C2) is 124°F or higher and less than
142°F, the revolution of the compressor is
controlled to prevent the high pressure being
increased.
(3) If MAX (C1, C2) is 142°F or higher, the compressor
stops once. The compressor restarts three times,
and if the temperature dose not decrease to less
than 142°F, the alert "P20" is displayed.
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