8.7.3 Operating principle 8.7.4 Electrical symbol 1. Common contact 2. Contact closed on "empty" 4. Contact closed on "full" 8.7.5 Circuit diagram 11-21-31: "Common" contact 12-22-32: "Empty" contact 14-24-34: "Full" contact 8.7.6 Checking for efficiency Correct operation of the pressure switch depends on the correct operation of its hydraulic circuit (tube and pressure chamber): Check for leaks (in which case too much water would be introduced, as the switch would not close on "full" or, in the event of microleakage, would return to "empty". Check for obstruction (in which case the contacts may be jammed on "full" or "empty"). After checking the hydraulic circuit:
Introduce water into the tub to the highest level and check that the contacts close correctly on "full". Drain the water from the tub and check that the contacts close correctly on "empty". SOI/DT 2002-05 eb 70 599 35 23-17 Tub empty Water flows into the tub Water is drained from the tub As there is no water in the tub, there is no pressure on the diaphragm, which thus remains in the lower position due to the counterforce exerted by the spring. In this position, the contact is closed on "empty". When the connection between the tub and the pressure chamber is interrupted by the water, the pressure between the pressure chamber and the internal chamber of the pressure switch increases.
This increase continues until the diaphragm is raised sufficiently to action the switch (rapid-action). In this position, the contact is closed on "full". As the level of water in the tub diminishes, the pressure exerted on the diaphragm is reduced. The diaphragm is pushed downwards by the counterspring until the switch resets (i.e. returns to the "empty" position).