Automatic washing machines control the water supply and level primarily using two key components: an electric solenoid valve and a pressure switch.
Here's a breakdown of how they work together to manage water during a wash cycle:
Key Components for Water Control
Based on how automatic washing machines operate, controlling water flow and level is essential for efficient cleaning. The main elements responsible are:
- Electric Solenoid Valve: This component acts like an electronic tap. It's an electrically controlled valve that opens and closes the water supply line.
- Pressure Switch: Also known as a water level switch, this device measures the amount of water in the wash tub based on the pressure exerted by the water.
How Water Supply is Controlled
The actual flow of water into the machine is managed directly with an electric solenoid valve.
- Function: When the washing machine's control panel signals that water is needed (e.g., at the start of a fill cycle), it sends electricity to the solenoid valve. This electrical signal energizes a coil inside the valve, which pulls open a piston or diaphragm, allowing water from your household supply to flow into the drum.
- Location: These solenoids are typically located on the back of the machine where the water inlet hoses connect. Many machines have separate valves for hot and cold water, allowing the machine to mix water to achieve the desired temperature based on the selected wash cycle.
- Operation: When the machine needs to stop filling, it cuts off the power to the solenoid valve, causing the piston or diaphragm to return to its closed position, shutting off the water flow instantly.
How Water Level is Controlled
Determining when to stop filling the tub with water is handled by the pressure switch.
- Function: Washing machines use a pressure switch to control the water level in the tub. A tube runs from the bottom of the wash tub up to the pressure switch, which is usually located near the control panel. As water fills the tub, the air trapped in this tube is compressed. The pressure switch detects this increasing air pressure.
- Operation: The pressure switch is calibrated to trigger at specific pressure levels, corresponding to different water heights in the tub (e.g., low, medium, high fill levels). When the desired water level is reached, the pressure in the tube reaches the switch's set point, activating the switch. This signal is sent back to the machine's control system.
- Role in Stopping Fill: Once the control system receives the signal from the pressure switch that the target water level has been reached, it then de-energizes the electric solenoid valve, stopping the water inflow.
Working Together: Solenoid Valve and Pressure Switch
Those two devices together are what is needed for basic automatic water control in a washing machine.
| Component | Primary Function | How it Works | Signal/Trigger | Location (Typical) |
|---|---|---|---|---|
| Electric Solenoid Valve | Controls water flow (On/Off) | Electrically opens/closes water line | Electrical signal from control | Back of the machine (inlets) |
| Pressure Switch | Controls water level | Detects pressure from water level in tub | Pressure from water level in tub | Top of the machine (with controls) |
The washing machine's control system (electronic or mechanical timer) orchestrates these components:
- Select a wash cycle (which dictates the required water level).
- Control system opens the appropriate solenoid valve(s) to start filling.
- As the tub fills, the pressure in the air tube increases.
- The pressure switch monitors this pressure.
- When the pressure reaches the level corresponding to the selected fill height, the pressure switch signals the control system.
- The control system then closes the solenoid valve(s), stopping the water flow.
This integrated system ensures the machine uses the correct amount of water for each load and stage of the cycle without requiring manual intervention.
