Basic Wiring Help: Learn How to Wire an Instrument

[PetePetePete]

Hi,

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
Pete

 

[PetePetePete]

Attached is what I think needs to be done, but would appreciate someone confirming?

Thanks

 

[anorlunda]

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.