Quick domestic wiring question...

What should the potential difference between live and earth be on a normal domestic wiring circuit? Obviously between live and neutral its around 240v, but I’m getting 240v between live and earth, suggesting there is earth leakage somewhere? Or simply that someone has wired neutral to earth?

I understand electronics…but not its practical application in domestic wiring…


Shouldn’t it be 230-240 live to neutral, 230 live to earth and 0-5v neutral to earth?

Yep, I’d be pretty worried if you weren’t seeing 230V to earth on a single phase installation! Somewhere down the line your earth and neutral will be tied together so the difference should be small. If the neutral gets too high then you’ve got earth leakage somewhere.

Every electricians nightmare when doing safety checks on other people wiring installations. The earth will work quite well as a neutral but it’s not what you might call “safe”.

The probable cause is a earth/neutral swap in a socket. (Well, that’s the most common and doesn’t show up on some circuit testers.) But the same thing in a plug top or permanent appliance connection can cause the same result.

Anybody change anything lately? Check that work first.

The “only” practical way is to unplug everything and then do a visual check on all connections working logically circuit by circuit with that circuit turned off at the distribution board. (Fuse pulled out if you have an old installation.)

There is a quicker way but I am sure not going to tell you that one as it’s not for anybody except qualified electricians.

Oops. Forgot something pretty basic.

You will almost always get a 220/240 v reading between live and earth if the earth conductor is good.

There may be nothing wrong!

Yes you should get a reading between Live & Earth. It shows that your earth is good.