What is the simplest switch circuit I can build for a 30-amp (220v) machine?

Thread Starter


Joined Oct 9, 2022
I was considering using a Rele but they don't work very well with high current (the ones that work are expensive) since its a high current I need the circuit to hold and at the same time not have much resistance when the current is passing through it. Is there any circuit I could use? I think that maybe there are some circuits with transistors but I'm not an expert on it so I'm seeking some advice from you guys!


Joined Jul 18, 2013
Depends somewhat on the nature of the machine!
If this is a connection to the local grid power then a contactor is required, with suitable fusing and overloads, maybe required.
If not included already with the equipment.


Joined Jan 23, 2018
An adequate power relay for (whatever) the machine is will not be so very costly, depending upon where you are located . Like theone in the photo in post #6, although there are less expensive two pole relays available.
But since we have no more information, that suggestion is as good as it gets.


Joined Jul 18, 2013
If the simplest solution is allowed, There is also the DP 30A switch as used in HVAC systems and available at home Depot etc.
Depends what is inherent in the machine. ! ;)


Joined Jan 23, 2018
The TS mentions "high current" without any mention of either the actual current or the voltage.
The TS also is listed as a "test engineer", who should, as any engineer should, be able to provide a more descriptive set of terms for the application.
And also, have a better understanding of the application.
What voltage range? Mains or battery? and what sort of current? A few amps or many amps?
Without a more detailed description there is no point in suggesting any solutions.


Joined Nov 29, 2005
My household air handler electric circuit switches with cheap relays that have proven so far to be reliable.

There are time delayed and several types. Coil is 24 VAC. Abundant free at a climate repair company dump.

The black one by the right (1); powered by the control transformer at lower left (2).


I may have half a dozen spares behind the spiders.