Thread: Grounding a circuit breaker

Hi Chris and a 70 amp circuit breaker is huge if you are just powering some electronics.

First off, the cable needs to be 4B&S ( 20mm2 ) as this is the thinest size cable you can safely use with a 70 amp circuit breaker.

Next, to test the circuit breaker, again as long as you have the correct size cabling. After connecting from the battery to one side of the circuit breaker, connect a cable to the other side of the circuit breaker and then just touch the end of this cable to earth.

The circuit breaker should trip just about instantly.

If it does not, REMOVE THE CABLE FROM EARTH.

thanks drivesafe.
The amps add up surprisingly quickly.
The fuse panel is actually rated to 80 Amps.

A 20amp power socket here
15 amp spotlights
10 amp radio
10 amp reverse spotlights
10 amp cb
5 reverse camera
5 fan

and wow I just realized I'm actually over the panel limit (If I have everything on at the same time)

I'm using 4 guage wire, which the guy at battery world tells me is good for up to 200AMP

Still confused: Does it matter if the breaker is earthed to the battery or the chassis?

I think it's faulty. currently earthed to the battery; touching the live wire to the body (creating sparks) does not trip the breaker

Hi again Chris and not sure how you have the CB wired up, but under normal installations, it should not be earthed to anything.

You should have battery positive coming from the battery's POSITIVE ( + ) terminal to the input ( marked BAT ) side of the CB and run another cable to your fuse panel positive connection from the output ( marked AUX ) side of the CB.

The CB's case is not grounded and there is no EARTH ( - ) connection on a circuit breaker!

you are correct, my brain is not working, or had something confused, I feel like an idiot.

So yes, no grounding. wiring in battery -> Breaker->fuse block.
I must have a dodgy breaker for it not to flip if I touch the cable going from the breaker to the fuse block to the chassis.

back to Jaycar for a replacement.

Originally Posted by drivesafe

Hi again Chris and not sure how you have the CB wired up, but under normal installations, it should not be earthed to anything.

You should have battery positive coming from the battery's POSITIVE ( + ) terminal to the input ( marked BAT ) side of the CB and run another cable to your fuse panel positive connection from the output ( marked AUX ) side of the CB.

The CB's case is not grounded and there is no EARTH ( - ) connection on a circuit breaker!

It's still to be purchased. I assumed that it would be like a radio and have an earth wire.
the things you learn!

That light bypass assembly of yours looks good. might have to invest in one when funding permits. A glow worm would laugh at my headlights

DO not go straight to earth.

go through the startermotor, hook it up to that and then try to start the engine or put a winch under load and try to use that. hell in a pinch grab a welding rod or a carvon pile and try to draw a spark.