DaveInDenver
Middle Income Semi-Redneck
As @Dave in AZ says, don't be scared of anything. Switching the hot (positive) or return (negative) side makes no difference in the circuit function electrically. You interrupt the flow of current just the same either way, the battery and load don't know the difference.
Technically a fuse also doesn't know where in the circuit it is. But you want to keep the fuse or breaker only on the hot side for safety if the chassis is negative.
This is what we'd call a "fault" meaning it's not the normal operation. You want the fuse as far up the source as possible to protect the wire and everything behind it. For a large feeder put the fuse at the battery, for one example. That's because anything on the battery side of the fuse is not protected.
I only mentioned it because sometimes you see combined units that have both a circuit protection and switch integrated. So if you're using something like that then you have to be aware it's possible to make a mistake.
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