What does a solenoid do on coffee machine?

A solenoid valve on an espresso machine is designed to control the flow of water during the coffee-making process. It has a small hole which regulates the amount and timing of water that is delivered into the filter cup at the right pressure.

During the brewing cycle, when you press the appropriate buttons on the control panel, the solenoid valve opens to enable the pump to deliver water into the filter cup at the right pressure. The pressure should be between 9 and 10 atmospheres (or bars) to ensure optimal coffee extraction. Upon deactivation, the valve immediately shuts to prevent further water from entering the brewing chamber. This mechanism ensures that the user has precise control over the brewing process and produces consistent espresso shots.

The solenoid valve also serves another vital function in the modern coffee machine. After brewing, it opens in a reverse manner to release the pressure that has built up in the filter cup, allowing the grounds to expand in a process known as the "post-infusion" phase. This final stage is crucial for enhancing the flavour extraction from the coffee grounds and creating a more complete espresso.

To preserve the longevity and performance of the solenoid valve, it is essential to ensure that the water supply to the coffee machine is free of impurities and calcium deposits. Regular maintenance and occasional descaling of the coffee maker help prevent the solenoid and other critical components from accumulating scale and malfunctioning.