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2
MSZ,MSY MICROPROCESSOR CONTROL
MSZ-A09NA MSY-A15NA MUZ-A09NA MUY-A15NA
MSZ-A12NA MSY-A17NA MUZ-A12NA MUY-A17NA
MSZ-A15NA MSY-A24NA MUZ-A15NA MUY-A24NA
MSZ-A17NA
MSZ-A24NA
2-1. COOL (
) OPERATION
1. Thermostat control
Thermostat is ON or OFF by difference between room temperature and set temperature
Room temperature minus set temperature : -1.8 degrees or more·····································ON
Room temperature minus set temperature : less than -1.8 degrees···································OFF
2. Indoor fan speed control
Indoor fan operates continuously at the set speed by FAN SPEED CONTROL button
regardless of the thermostat's OFF-ON.
In AUTO the fan speed is as follows.
Room temperature minus set temperature : 3.1 degrees or more ·······························High
Room temperature minus set temperature : Between 1.8 and 3.1 degrees ···················Med.
Room temperature minus set temperature : less than 1.8 degrees ····························Low
3. Coil frost prevention
Temperature control
When indoor coil thermistor detects following temperature for 90 seconds, operational frequency
of compressor is controlled according to the following table.
Temperature of indoor coil thermistor
50°F or more
46°F to 50°F
43°F to 46°F
37°F to 43°F
37°F or less
The indoor fan maintains the actual speed of the moment.
4. Low outside temperature operation
If the outside temperature falls to 64°F or less during operation in COOL mode, the unit enters the low outside temperature
operation mode.
<Operation>
(1) If the unit enters the low outside temperature operation mode, the outside fan rotation speed gets slow down.
(2) Even when the unit is in the "thermostat-off" status under the low outside temperature operation mode, the outside fan
rotation does not stop.
(3) In this mode to detect the exact outside temperature the compressor turns OFF with the outdoor fan ON for 3 minutes
once 1 hour; if the outside temperature rises over 64°F, the unit goes back to the normal COOL mode, and if the
outside temperature is still 64°F or less, the unit stays in the low outside temperature operation mode.
(4) Dew drop prevention
When the ambient temperature thermistor RT65 reads 10°F or less, as coil frost or dew drop from indoor unit may
occur, the compressor turns OFF with the outdoor fan ON for prevention of them.
WOther protections work as well as in the normal COOL mode.
MUZ-A17NA
MUZ-A24NA
Initial temperature difference
Initial temperature difference
Compressor is turned OFF for 5 minutes when temperature of
indoor coil thermistor continues 37°F or less for 5 minutes or more.
6
Difference between room
temperature and set temper-
ature during operation.
Thermostat
Difference between room
temperature and set temper-
ature during operation (
Fan speed
Operation frequency
Normal (variable)
Raise 6Hz
Fixed
Lower 3Hz
Lower 6Hz
Set temperature
-1.8deg.
-1.3deg.
T)
5.4deg.
1.8deg.
3.1deg.
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