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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.Processes and functions
(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
(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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