2. Processes and functions
Overcurrent protection control
(1)If the overcurrent protection circuit detects abnormal current, the compressor is stopped. (Error count = 1.) The compressor then restarts after 3 minutes.
(2)If compressor start/stop is repeated 4 times (error count = 4), alarm "P26", "P29" or "H01" (count = 2 in this case only) occurs. Operation stops and does not restart.
Current release value shift control
(1)This control is intended to improve compressor reliability by preventing continuous
(2)The control value for "current release control" is corrected according to the outdoor air temperature (TO).
Depending on the temperature, the control value is lowered to 50 – 90% for cooling operation, and to 60 – 98% for heating operation.
Freeze prevention (low-temperature release) control
The below control is performed during cooling operation (including dehumidifying operation), using whichever of the indoor heat exchanger temperatures (E1 or E2) is lower. (See the figure below.)
(1)If a temperature in the "J" area (operating frequency reduction and thermostat OFF area) is detected for 6 minutes, the compressor operating frequency is reduced. The compressor operating frequency is reduced every 30 seconds as long as the temperature remains within this area.
(2)If the temperature is in the "K" area (operating frequency
(3)If the temperature is in the "H" area (operating frequency control area), and the outdoor air temperature is less than 90°F, the compressor maximum operating frequency is limited according to the indoor unit fan speed.
(4)If the temperature is in the "I" area (normal operating area), the compressors operate normally.
(5)If the temperature is continuously in the "J" area and the compressor operating frequency reaches 0, then temperature A (temperature for changing from "J" area to "H" area) is raised from 41°F to 46°F, and operation continues with the thermostat OFF until the temperature reaches the "H" area.
Heating high-load control
The below control is performed during heating operation, based on the indoor heat exchanger temperature MAX (E1,E2).
(1)If the temperature is in the "M" area (operating frequency reduction and thermostat OFF area), the compressor operating frequency is reduced.
The compressor operating frequency is reduced every 30 seconds as long as the temperature remains within this area.
(2)If the temperature is continuously in the "M" area, the thermostat turns OFF.
(3)If the temperature is in the "N" area, operating frequency increases are prohibited.
(4)If the temperature is in the "L" area, the operating frequency is raised to the original frequency (the frequency prior to frequency reduction) by 6 Hz every 60 seconds.
(30, 36, 48 types)
*When the compressor turns ON and the E2 temperature rises, the temperature at which the "M" area is first entered is 124°F (30, 36, 42 types) or higher than 129°F (26 type).
If the E1, E2 temperature subsequently falls to the "L" area, the temperature for entering the "M" area is raised to 126°F (30, 36, 42 types) or 133°F (26 type).
However if the E1, E2 temperature falls to the "L" area and falls below 86°F, then the temperature for entering the "M" area is changed back to 124°F (30, 36, 42 types) or 129°F (26 type).
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