Daikin VRV – Structure and Operation of Electronic Expansion Valve

For VRV system, EBM type linear control valve is employed to use as an electronic expansion valve for superheated degree control or subcooled degree control.
In the valve, single-phase excitation drive type pulse motor is employed. On receiving 2000 pls signal, goes to full open. The stroke of gear is 0.7 mm from full open to complete close. The below figure shows the inside structure of driving section, and the gear ratio is 1 / 30.

Malfunction Example of Electronic Expansion Valve

Gas Leakage

Malfunction (Full Open)

Malfunction (Complete Close)

The valve is protruded excessively into the valve seat. When driving section of electronic expansion valve is removed during operation, default setting (initialize) shifted and the output shaft may be incorrect position. If this operation is repeated, protrusion of valve cannot be returned.
Above cause of the trouble may be result leakage of motorized valve (inner leakage).

When electronic expansion valve is removed during the unit is operated, make sure to conduct initialization before ending of the work.