Expansion Valve Control/Lev Control - Mitsubishi Electric MSC-GE-VB Service Manual

MUZ-EF
Pre-heat control ON condition
(1) Compressor is not operating. (However, pre-heat control is still OFF for 60 minutes after compressor is stopped,
regardless of the compressor temperature.)
(2) Compressor temperature is monitored hourly, and when the compressor temperature is 20°C or below, pre-heat con-
trol is turned ON.
(3) When the compressor temperature exceeds 30 °C, pre-heat control is turned OFF.
When pre-heat control is turned ON, compressor is energized about 50 W (40-60 W). (Compressor and fan are not operated.)
2-11. EXPANSION VALVE CONTROL/LEV CONTROL (MUZ-GC/FD/GE/EF/HC35VA(B)-
(1) Outline of LEV control
The LEV basic control is setting of LEV opening degree to the standard opening degrees set for each operational fre-
quency of the compressor. However, when any change in indoor/outdoor temperatures or other factors cause air condi-
tioning load fluctuation, the LEV control also works to correct LEV opening degree based on discharge temperature (Shell
temperature) of the compressor, developing the unit's performance.
Control range
Actuating speed
Opening degree adjustment
Unit OFF
Remote controller ON
During 1 to 15 minutes after compressor starts
More than about 15 minutes have passed since com-
pressor start-up
Thermostat OFF
Thermostat ON
Defrosting in HEAT mode
(2) Time chart
Air conditioner ON
Opening degree is
Positioning
corrected according
to discharge
temperature.
Standard
(Refer to (3))
opening
degree
About 15 minutes
ON
Minimum : 54 pulse
Maximum : 500 pulse
Open: 40 pulse/second
Close: 90 pulse/second.
LEV opening degree is always adjusted in opening direction.
(When reducing the opening degree, LEV is once over-closed,
and then adjusted to the proper degree by opening.
LEV remains at maximum opening degree. (LEV is reached
maximum opening degree approximately in 15 minutes after
compressor stops.)
LEV is positioned. (First LEV is full closed at zero pulse and
then positioned.)
LEV is fixed to standard opening degree according to opera-
tional frequency of compressor.
LEV opening degree is corrected to get target discharge tem-
perature of compressor.
(For lower discharge temperature than target temperature,
LEV is corrected in closing direction.)
(For higher discharge temperature than target temperature,
LEV is corrected in opening direction.)
It may take more than 30 minutes to reach target tempera-
ture, depending on operating conditions.
LEV is adjusted to exclusive opening degree for thermostat
OFF.
LEV is controlled in the same way as that after the compres-
sor has started up.
LEV is adjusted to open 500 pulse.
Air conditioner OFF
(thermostat off)
Commanded
to open
Time
OFF Time
22
)
E2