Expansion Valve Control (Lev Control) - Mitsubishi Electric MS-A WA Service Technical Manual

(1) Outline of LEV control

The LEV basic control is comprised of setting LEV opening degree to the standard opening degrees set for each opera-

tional frequency of the compressor. However, when any change in indoor/outdoor temperatures or other factors cause

air conditioning load fluctuation, the LEV control also works to correct LEV opening degree based on discharge tempera-

ture (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 compressor start-up

Thermostat OFF

Thermostat ON

Defrosting in HEAT mode

(2) Time chart

Minimum: 33 pulses (MUZ-A09/12/15/17 MUY-A15/17)

Maximum: 500 pulses

Open: 40 pulses/second

Close: 90 pulses/second

LEV opening degree is always adjusted in opening direction. (When reduc-

ing the opening degree, LEV is once over-closed, and then adjusted to the

proper degree by opening.

LEV remains at maximum opening degree (reaches maximum opening

degree approximate in 15 minutes after compressor stops)

LEV is positioned. (First full-closed at zero pulses and then positioned.)

LEV is fixed to standard opening degree according to operational frequen-

cy of compressor.

LEV opening degree is corrected to get target discharge temperature of

compressor.

(For lower discharge temperature than target temperature, LEV is correct-

ed in closing direction.)

(For higher discharge temperature than target temperature, LEV is cor-

rected in opening direction.)

It may take more than 30 minutes to reach target temperature, depend-

ing on operating conditions.

LEV is adjusted to exclusive opening degree for thermostat OFF.

LEV is controlled in the same way as that after the compressor has started

up.

LEV is adjusted to open 500 pulses

Air conditioner ON

Positioning

Opening degree is

corrected according

to discharge

temperature.

Standard

(Refer to (3))

opening

degree

About 15 minutes

ON

59 pulses (MUZ-A24 MUY-A24 MUZ-GA MUY-GA)

54 pulses (MUZ-FD MUZ-FE MUZ-GE MUY-GE)

58 pulses (MUZ-D MUY-D)

Air conditioner OFF

(thermostat off)

Commanded

to open

Time

OFF Time

18