8.7 Pressure switch 8.7.1 General characteristics The function of the pressure switch is to determine the quantity of water to be introduced into the tub. In other words: Ц It controls the water fill levels during the washing phases. Ц It acts as an anti-boiling safety device when connected in series to the heating element. Ц It can also act as an anti-overflow safety device if connected in series to the drain pump. Ц It can act as an anti-foam device during the spin phases. 1. Air inlet aperture 2. Diaphragm 3. Internal chamber 4. Contact strip (rapid cut-in) 5. Level regulation screw 6.
Differential regulation screw The internal chamber is connected via a small tube to the pressure chamber. When water is introduced into the tub, the pressure in this chamber increases. When the pressure reaches a pre-determined level, the membrane causes the contact strip to trip (rapid-action), which switches the contact from "empty" to "full". Two regulation screws are fitted to the cover, one for the level, the other for the differential, i.e. the point at which the strip returns to the "empty" position when the level of water in the tub decreases. 8.7.2 Pressure switch hydraulic circuit 1. Pressure switches 2. Tub 3. Filter body 4. Pressure chamber on filter body 5.
Pressure chamber on the tube between the tub and the filter body 6. Pressure switch tubes ѓ Normally, all appliances are fitted with one or two pressure switches (in rare cases, an appliance may feature three pressure switches). Each pressure switch controls from one to three levels of water in the tub. ѓ The small tube from the pressure switches may be connected to the pressure chamber, which is located beneath the tub (this is the most common solution) or to that on the filter body. ѓ One or two pressure switches may be connected to the pressure chamber, depending on the model. SOI/DT 2002-05 eb 69 599 35 23-17