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MICROPROCESSOR CONTROL
10
OUTDOOR MICROPROCESSOR CONTROL
1. Protection function
(1) As soon as a reversed phase, an open phase, or a P. C. board trouble is sensed, the operation stops and the check
code is displayed by LED on the outdoor controller board.
(2) When a protection function such as high pressure switch and overcurrent relay works for the first time, the operation
stops and restarts after 3-minute time delay mode. When the second protection function works, the operation stops
and the check code is displayed by LED. This condition continues until the outdoor unit receives OFF command from
the indoor controller board. Check code indication continues until the outdoor unit receives the ON command from
the indoor controller board.
(3) The second protection function is not necessary to be the same as the first one. The content of the second protection
function is loaded in the memory, which is cleared when SW1 turns to ON or the next check mode starts.
2. Control by outdoor coil thermistor
(1) Unit control
Outdoor coil temperature range for control is from -40˚F to 194˚F. When reading 194˚F or above, the outdoor coil
thermistor is regarded as short-circuit. When reading -40˚F or below, the outdoor coil thermistor is regarded as
open-circuit. An open circuit is not sensed for the first 7 min. after the compressor start up, but is sensed during
defrosting operation or for the first 10 seconds after the compressor start-up.
(2) Target temperature of outdoor coil temperature
Fan rotational frequency is controlled so that the outdoor coil temperature keeps 95˚F ± 4˚F.
3. Unit operation control
The compressor receives signal from the indoor unit and make the outdoor unit start or stop.
4. Fan control
Fan rotational frequency is phase-controlled so that the outdoor coil temperature reaches the target temperature.
This control enables cooling operation even if the outdoor temperature is low. Fan rotational frequency is adjusted by fan
output. Fan output is divided into 256 steps from 0 to 255 and is controlled every 30 seconds.
(1) Initial setting
A. When power is turned to on, or when the compressor restarts after interval of 30 minutes or more :
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If the outdoor coil thermistor reads 46˚F or below, the fan output step becomes 100.
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If the outdoor coil thermistor reads above 46˚F, the fan output step becomes 200.
B. When the compressor restarts within 30 minutes after stop, the fan output step is the same as the fan output before
the compressor stops.
C. When the operation mode is changed within 30 minutes after the compressor stop, the fan output step becomes 100.
D. When the operation mode is changed after the compressor interval of more than 30 minutes, the fan output step is
the same as described in A.
(2) For the first 2 minutes after the compressor start-up, the fan operates at the initial setting output, and then every other
30 seconds, the fan output is adjusted depending on the difference between the outdoor coil temperature and the
target temperature. But as soon as the outdoor coil temperature becomes 122˚F or above, the fan output step becomes 255.
(3) When the outdoor coil thermistor reads 122˚F or above, the fan output step becomes 255.
(4) When the high pressure switch (63H1) functions, the fan output step becomes 255. After that, when the switch returns,
the fan control returns to the normal control.
5. Crankcase heater control
(1) With jumper wire J3
The crankcase heater is ON from the power is turned to on till the compressor starts, and turns to ON 1 hour after the
compressor stop.
(2) Without jumper wire J3
The crankcase heater is ON from the power is turned to on till the compressor starts, and repeats ON/OFF on a 1-hour
schedule.
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