Water Level Sensing Switch

keeping their respective valve ports closed. The ports open only when electrical power is sent to the solenoid windings. WATER VALVES.—The water valves control the inflow of hot and cold water during fill operations. The valves are electrically operated, as shown in figure 5-29. The solenoids are turned off most of the time, The two water valve solenoids can be operated individually or at the same time. Activating the "hot" valve, for instance, fills the washer with hot water. Energizing the "cold" valve fills the washer with cold water, and energizing both valves at the same time fills the washer with warm water—a mixture of hot and cold. The water temperature selector switch determines the water valves to be operated during any given fill operation; timer contacts are responsible for energizing the selected solenoids at the appropriate times. A typical water-fill circuit for modern automatic washers is shown in figure 5-30. The hot- and cold-water solenoid valves are energized through several sets of timer contacts and a water temperature selector switch assembly. WATER LEVEL SENSING SWITCH.— Washers that do not use a timed-fill interval must have provisions for sensing the water level and turning off the water supply whenever a given water level is reached. This sensor normally takes the form of a pressure switch that is activated either directly by the water pressure on the bottom of the laundry tub or indirectly activated by air pressure in a tube located at the rear of the washer. The diagram in figure 5-31 shows the operation of the indirect, or air pressure, sensing mechanism. The water level in the tub is always the same as the water level in the washer. As the water level rises, the air pressure at the top of the tub increases. A pressure switch at the top of the tub can be adjusted to close at various pressure levels, representing different water levels in the washer. ongoing operation. DOOR INTERLOCK SWITCH.—The door interlock switch is a safety feature that completely shuts down the washer whenever the door or lid is opened during a spin operation. Opening the door during any other part of the cycle does not affect the The diagram in figure 5-32 shows how the door interlock switch is bypassed by a timer contact. The timer contact is closed throughout most cycles of the washer, allowing the lid switch to be opened without interrupting current flow to the motor circuit. During every spin operation, however, the timer opens the bypass switch, letting the lid switch interrupt the complete circuit to the motor whenever the lid is opened during that particular operation. This list of mechanical and electrical components is not complete as far as the full range of modern clothes washer models is concerned. This list is complete, however, in the sense that it describes the most critical components and those that are unique to clothes washers. Installation Satisfactory performance of an automatic washing machine depends on a carefully planned and properly designed first installation. The place where the laundry is done should be well lighted and adequately equipped with convenient electrical outlets. The plumbing connections must be anchored to the floor to prevent movement. Figure 5-29.—Hot- and cold-water solenoid valve control system. 5-28