This was a lot of fun to reverse engineer. Mainly because it's very old-school inside. It's an automatic changeover switch for a backup generator supply. When power fails and the generator starts, the switch will automatically transfer over to the generator. When the power returns it will switch back over to the main supply.
The issue with the relay being energised all the time and to make it generator-priority could be addressed by simply swapping the sides the main and generator power are attached to. That way the generator would take priority in the event of a power failure and not switch back until it was turned off, and the relay would only be energised when the generator was running.
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11 thoughts on “Automatic generator changeover switch with schematic .”
  1. Avataaar/Circle Created with python_avatars Paul Maxwell says:

    Great video. I just might buy one to play around with. I do wish you had dismantled one of the switches to see if a) these are circuit breakers or just switches and b) the contacts are even close to adequate for the current rating. The Chinese are notorious for claiming a 20A switch contact can handle 40 or 60 A. Of course, they soon burn up.

  2. Avataaar/Circle Created with python_avatars Chris Call says:

    Ive had two of these now and both have failed at the breaker/switch internal contacts. They get hot and warp which causes them to lose contact. It would be great if someone found a properly rated replacement breaker.

  3. Avataaar/Circle Created with python_avatars Agguilar Metal work says:

    Hi thanks for the video 👍🏻 can you make a video of the ac/dc inverter minisplit they automatically switch from ac to dc solar, that will be good to see how they work

  4. Avataaar/Circle Created with python_avatars Alex Attis says:

    For our American panels, you can get what is called a generator interlock kit, where you have the breaker from the generator input (and also a proper twist-lock male power connector on the side of the house that actually plugs into the generator), as well as a piece of metal that will go on the main breaker and the generator breaker, and prevent both from being on at the same time, so you can't backfeed and can't get a shock from the exposed metal on the male power connector.

  5. Avataaar/Circle Created with python_avatars Alex Attis says:

    It is probably hackable to put a reputable DIN rail switch inside, so you could feel better about actually installing it, although I still wouldn’t recommend it.

  6. Avataaar/Circle Created with python_avatars nitrous dude says:

    if the motor failed, during a transfer…. is it possible for the two banks of breakers to be closed?

  7. Avataaar/Circle Created with python_avatars tuxcrafter says:

    How can I turn on my generator inverter with a two wire auto generator start with an ATS?

  8. Avataaar/Circle Created with python_avatars Danielle Meeks says:

    Could they of used an inverter ic to make the relay work?

  9. Avataaar/Circle Created with python_avatars Stephen Belcher says:

    Landed Hi Again Clive: That looks interesting what you’re Doing Philosophy😃

  10. Avataaar/Circle Created with python_avatars Troy Pointer Photography says:

    Hi this is Troy – I would like to use one of these as I want to power SOLAR during the day to my house PC and Monitor and others – then for it to change over to my extension lead drawing power from my mains electric can you tell me how and can you send an email with a diagram layman terms please
    Thanks Troy

  11. Avataaar/Circle Created with python_avatars Niko says:

    thought u said 20 watts

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