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MSZ,MSY MICROPROCESSOR CONTROL
2
2-1. COOL ( ) OPERATION
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.
1. Thermostat control
Thermostat is ON or OFF by difference between room temperature and set temperature
ON -1.8 °F or more
OFF less
than
-1.8 °F
-1.3 °F
Room temperature minus
set temperature (During operation)
Room temperature minus
set temperature (Initial)
Thermostat
-1.8 °F
High 3.1 °F or more
Med. between 1.8 and 3.1 °F
Low less than 1.8 °F
3.1 °F
5.4 °F
1.8 °F
Fan speed
Room temperature minus
set temperature (Initial)
Room temperature minus
set temperature (During operation)
3. Coil frost prevention
The compressor operational frequency is controlled to prevent the temperature of indoor heat exchanger from falling exces-
sively.
The compressor is turned OFF for 5 minutes when the temperature of indoor coil thermistor continues 37 °F or less for 5
minutes or more.
The indoor fan maintains the actual speed of the moment.
High 2.7 °F or more
Med. between
1.8 and 2.7 °F
Low less than 1.8 °F
2.7 °F
5.4 °F
1.8 °F
Fan speed
Room temperature minus
set temperature (Initial)
Room temperature minus
set temperature (During operation)
MSZ-A
MSY-A
MSZ-FD
MSZ-D
MSY-D
4. Low outside temperature operation
If the outside temperature falls to 64 °F or less during operation in COOL mode, the unit will switch to the low outside tem-
perature operation mode.
<Operation>
(1) Outdoor fan control
The outdoor fan rotation speed slows down to maintain sufficient cooling capacity.
NOTE: Even when the unit is in the "thermostat-off" status under the low outside temperature operation mode, the out-
door fan rotation does not stop.
(2) Dew drop prevention
When the ambient temperature thermistor reads 10 °F (MUZ-A MUY-A MUZ-D MUY-D), -4 °F (MUZ-FD) 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.
(3) Outdoor temperature detecting control
To detect the exact outdoor temperature in this mode, the compressor turns OFF but the outdoor fan stays ON for 3
minutes once 1 hour. If the outdoor temperature rises over 64 °F, the unit goes back to the normal COOL mode. If the
outside temperature stays below 64 °F, the unit continues to run in the low outside temperature operation mode.
Other protections work as well as in the normal COOL mode.
MSZ-A•NA MSY-A•NA MUZ-A•NA MUY-A•NA
MSZ-FD•NA MSY-D•NA MUZ-FD•NA MUY-D•NA
MSZ-D•NA MUZ-D•NA