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Continuous Duty Relay-Solenoids

Bulletin 3010

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Auxiliary equipment such as snowplows and winches requiring high amperage continuous power.



This bulletin will explain how continuous duty relay/solenoids work and how they are different from an intermittent duty starter solenoid.


Just as their name implies a continuous duty relay/solenoid is designed to operate continuously providing voltage to a higher amperage circuit. There are a few different types of these solenoids and many different uses. Just like the standard automotive starter solenoid, continuous duty relay/solenoids are an electronic switch. When commanded on, internally an electromagnetic force activates the contact plate and connects the main terminals to allow current to flow from the power side to the load or device you intend to power.


Continuous duty relay/solenoids have an amp rating while their counterpart, the automotive or intermittent solenoids do not. The higher amperage and continuous on time these solenoids are asked to operate within creates heat between the contacts which in an automotive type solenoid would cause the contacts to literally weld together. An automotive type solenoid is designed for short bursts, like 3-8 seconds on, and then allowed to cool until commanded on at the next start up.


Another type of continuous duty solenoid is called a latching solenoid. The latching solenoid can maintain a set position without constant power applied. De-energizing the internal magnetic force allows the solenoid to switch from one position back to the secondary position. So, like a true switch, on and off, it does not require a continual power source to operate the switch winding field. This type of solenoid is utilized primarily in battery only applications due to its low power consumption.  A common use would be a duel battery application where the user would want to isolate one battery from the other on command.


While similar in shape and function, the continuous duty and intermittent automotive starter solenoids are not interchangeable. 


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