Pre-Heat Control; Cool Operation - Mitsubishi Electric MS-A WA Service Technical Manual

3-7. PRE-HEAT CONTROL

MXZ-2A20NA- , MXZ-3A30NA-
1 2
MXZ-3B24NA MXZ-3B30NA MXZ-4B36NA
The compressor is energized even while it is not operating.
This is to generate heat at the winding to improve the compressor's start-up condition.
Power ON
OFF
Compressor ON
OFF
Defrost thermistor
69.8°F
(21°C)
Pre-heat ON
OFF
Breaker ON
1. Pre-heat control is turned ON for 15 or 30 minutes, after the breaker is turned ON.
2. 30 minutes after the unit is stopped, pre-heat control is turned ON for 15 or 30 minutes and turned OFF for 30 minutes.
This is repeated as shown in the graph until the breaker is turned OFF.
When the defrost thermistor reads less than 69.8°F (21°C), pre-heat control is ON for 30 minutes.
When the defrost thermistor reads 69.8°F (21°C) or more, pre-heat control is ON for 15 minutes.
NOTE: When the unit is started with the remote controller, pre-heat control is turned OFF.
Compressor uses 50 W when pre-heat control is turned ON.

3-8. COOL OPERATION

1. Thermostat control
Thermostat turns ON or OFF by the difference between room temperature and set temperature.
Thermostat
2. Coil frost prevention
The compressor operational frequency is controlled to prevent the indoor heat exchanger temperature from falling exces-
sively.
Compressor is turned OFF for 5 minutes when temperature of indoor coil thermistor continues 37.4°F (3°C) or less for 5
minutes or more.
MXZ-4A36NA MXZ-2B20NA MXZ-2B20NA-
1
30 minutes
Start
operation
Room temperature minus
set temperature (Initial)
ON
OFF
30 minutes 30 minutes 30 minutes 30 minutes
Stop
operation
-1.8°F(-1°C) or more
less than -1.8°F(-1°C)
33
1
15 15
30 minutes
minutes 30minutes minutes
When the defrost
thermistor reads
or more
69.8°F(21°C)
Room temperature minus
set temperature (During operation)
-1.8°F -1.35°F
(-1°C) (-0.75°C)
30minutes