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Basic Wiring Help!

  1. Jul 27, 2015 #1

    I have an electrical instrument which needs a 12V feed.

    I have 2 power systems, and I want to select between them using an On-Off-On switch. I presume an SPDT is appropriate?

    I need to run the feed to the instrument through a 3A circuit breaker.

    Please could someone explain how I should wire this up? I am not sure which terminals on the Switch and CB I should use!

    The instrument is expensive, and I need to be sure this is done properly!

    I have attached a graphic of what I mean.

    Many Thanks

    Attached Files:

  2. jcsd
  3. Jul 27, 2015 #2
    Attached is what I think needs to be done, but would appreciate someone confirming?


    Attached Files:

  4. Jul 27, 2015 #3


    Staff: Mentor

    Is this the only load to be served by those two batteries? If there are many, and if they may be large, then it is safest to use a "battery switch" for the ON-OFF-ON function in PetePetePete's diagram. They use a make-before-break system that prevents interruption before switching. They also include the ALL or BOTH position to use both batteries at once.

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