Auto Change Over - Mitsubishi Electric MS-A•WA Service Technical Manual

Time chart of defrosting in HEAT mode (reverse type)
<indoor unit>
set position
Horizontal vane
Indoor fan
set speed
<outdoor unit>
Compressor normal
Outdoor fan
R.V. coil
(21S4)
2-4. AUTO CHANGE OVER ··· AUTO MODE OPERATION (MSZ)
Once desired temperature is set, unit operation is switched automatically between COOL and HEAT operation.
1. Mode selection
(1) Initial mode
At first indoor unit operates only indoor fan with outdoor unit OFF for 3 minutes to detect present room temperature.
Following the conditions below, operation mode is selected.
1 If the room temperature thermistor RT11 reads more than set temperature, COOL mode is selected.
2 If the room temperature thermistor RT11 reads set temperature or less, HEAT mode is selected.
(2) Mode change
In case of the following conditions the operation mode is changed.
1 COOL mode changes to HEAT mode when 15 minutes have passed with the room temperature 4 degrees below the
set temperature.
2 HEAT mode changes to COOL mode when 15 minutes have passed with the room temperature 4 degrees above the
set temperature.
In the other cases than the above conditions, the present operation mode is continued.
NOTE1: Mode selection is performed when multi standby (refer to NOTE2) is released and the unit starts operation with
ON-timer.
NOTE2: If two or more indoor units are operating in multi system, there might be a case that the indoor unit, which is
operating in AUTO (
state of standby.
Very Low (temperature of indoor coil thermistor > 64°F)
30
seconds
Maximum frequency
OFF
40 30
seconds seconds
5 seconds
ON
ON (HEAT)
), cannot change over the other operating mode (COOL
horizontal
OFF
40
seconds seconds
OFF
OFF (COOL)
9
set position
set speed
OFF
30
5 seconds
ON
ON (HEAT)
HEAT) and becomes a