Solenoids are electromechanical devices used in irrigation systems to control the operation of control valves. They act as electrically operated switches that open or close the valve in response to signals from the irrigation controller or timer.
A solenoid consists of a coil of wire wrapped around a metal core. When an electrical current is applied to the coil, it creates a magnetic field that moves the core, which in turn activates the valve. Solenoids are typically low-voltage components that are safe to use in irrigation systems.
The solenoid is connected to the control valve and is typically housed within the valve box. When the irrigation controller sends a signal to the solenoid, it energizes the coil, causing the solenoid to open or close the valve, allowing or stopping the flow of water to the designated zone.
Solenoids play a crucial role in the automation and control of irrigation systems, allowing for precise and efficient water distribution by opening and closing valves according to programmed schedules or manual commands. They are an integral part of the overall functionality and automation of irrigation systems.
Operation and test
Irrigation solenoids are normally closed. A flexible membrane closes the way of water in the solenoid.
The magnet coil pulls in when the controller supplied the right voltage via the cables and opens a small hole on the membrane inside the solenoid body. The pressure is equalising between the two sides of the membrane and that is not able to hold the water back. The water is flowing through the body. When the electric circuit becomes open, the core of coil is falling back on the hole and the water is pushing back the membrane into its place and that will close the solenoid.
9V DC solenoids work a bit different because of saving electricity. These solenoids are operated by battery timers and controllers, hence the energy can be used is limited.
When the timer sends the opening signal to the coil of solenoid and the core is moved, there is a small latch that is fixing the core in its open position. This way continuous energy is not necessary to keep the solenoid open. When the timer wants the zone gets closed, the latch moves away and the solenoid will close.
They contain plastic and metal parts and affected by thermal expansion hence they are one of the most vulnerable parts of an irrigation system because of winter temperature changes. As most system includes solenoids the winter shut down service is highly recommended on our climate.
Best way of implementing the shut down when the water gets blown away from all parts of the irrigation system by a compressor. This is how The Gardener’s Rain makes the irrigation systems winter safe.
There are some possible faults with solenoids. When a zone remains open after its normal running time, the suspicion can be a small stone or other sediment stuck under the membrane.
In this case the top of the solenoid has to be removed. Majority of solenoids are assembled with screws but there are others with jar-top, which can be unscrewed.
Under the cover, there is a spring and the membrane (and mabe other smaller parts as well, depending on the type). Be sure, order of the parts won’t be swapped during the assembling process.
When the membrane is removed, it has to be checked against damage. Also the body of the solenoid has to be cleaned. Make sure, no dirt can be get into the solenoid body during the cleaning process.
When a zone doesn’t start, a continuity problem can be in the background. Amongst others, connectors of the cables to the solenoids worth to be checked and replaced because the lifetime of the commonly used gel connectors is somewhere around 5 years.
Despite careful maintenance body of a solenoid can get cracked after a while. In this case, the unit has to be replaced.