Ask The Trades - Print Page

Ask The Trades
https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> neutral connected to earth https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1240786259 Message started by speedmaster99 on Apr 26^th, 2009, 11:50pm

Title: neutral connected to earth
Post by speedmaster99 on Apr 26^th, 2009, 11:50pm

Hello, last night the lights in my kitchen blew a fuse. It seemed odd that they would just blow so this morning I turned the power off at the mains fuse box ( yes old 1960's semi & still uses fuses rather than circuit breakers) and got the multimeter out.

I checked the for shorts between the live and earth wires - nothing - not connected - but when I checked neutral to earth, they were connected.

Now I'm confused - is this correct, I always thought that the live and neutral formed the circuit but neither of them should touch the earth wire.

If I disconnect the neutral from the earth wire - will my house be any less safe?

Title: Re: neutral connected to earth
Post by speedmaster99 on Apr 27^th, 2009, 12:30am

I forgot to say that Earthing Arrangement is TN-S with the earth cable from the fuse box being bonded like this

http://www.axre59.dsl.pipex.com/images/meter_pos_TNS_sheath.gif

Title: Re: neutral connected to earth
Post by scotspark on Apr 27^th, 2009, 12:37am

could still be tncs

Title: Re: neutral connected to earth
Post by Lectrician on Apr 27^th, 2009, 6:44am

With the fuseboard turned off you should not have any continuity between neutral and earth.

Sounds like you have a neutral to earth fault somewhere in your installation (could be either circuit).

This is unlikely to be what caused the fuse to operate.

What type of lamps are in the kitchen light? Lamps can cause fuses to go these days when they fail due to cheaper production methods. Even the old BS3036 rewireables are known to blow.

Title: Re: neutral connected to earth
Post by CWatters on Apr 27^th, 2009, 7:40am

The halogen downlights we had in our last house seemed to trip the breaker every time a bulb failed. Normally reseting it allowed you to work out which one had blown and the rest was easy.

Title: Re: neutral connected to earth
Post by speedmaster99 on Apr 27^th, 2009, 7:50am

The lamps were Wicks/BnQ spotlights with 50W 240v philips A7's

I went round the house tracing this thing and found that on the downstairs sockets ring, in one of the connection boxes where the feed was taken off to the wall socket, earth and neutral had been cross connected. Looks like it has always? been that way or at least since the previous owner put the extra sockets in.

It probably explains why the metal face plate of the light switch 'tingled' when the light was switched on.

Looking at the fuseboard, it looks very much tns

Title: Re: neutral connected to earth
Post by Y3 on Apr 27^th, 2009, 8:23pm

When u isolated the circuit, was it the whole consumer unit or just the fuse?

Title: Re: neutral connected to earth
Post by speedmaster99 on Apr 27^th, 2009, 8:43pm

I switched off the switch isolating the fusebox then pulled all the fuses

3 ring circuits and one for the lights.

All equipment was unplugged from their sockets.

With the unit isolated the connection to earth was still there.

I disconnected each neutral in turn from the fuse box and checked for continuity with earth.

Once I identified which one it was in - it was just a case of lifting floorboards and looking in each of the connection boxes on the ring - and in one of them earth and neutral were crossed.

Title: Re: neutral connected to earth
Post by Lectrician on Apr 27^th, 2009, 9:18pm

Earth and neutral crossed :-/

Title: Re: neutral connected to earth
Post by CWatters on Apr 28^th, 2009, 8:18am

connection boxes on the ring?

PS: Most of us get a tingle when the bedroom light is turned off so something obviously wrong ;D

Title: Re: neutral connected to earth
Post by speedmaster99 on Apr 28^th, 2009, 8:59am

sorry - terminology - junction box - it looks like some one years ago - previous owner, had an extra socket added - and where the spur had been taken off the junction box, one side of the ring & the spur were wired in as L E N , but the other 'side' of the ring was wired in as L N E

So mistake or deliberate ?

Title: Re: neutral connected to earth
Post by Lectrician on Apr 28^th, 2009, 4:03pm

I fail to see how someone could manage to get different colour cables into the same terminal of joint box?

If it was a ring and it was crossed like this, because it is a ring it would short N to E. If it was a radial it would not cause a short, but would also not be right.

Title: Re: neutral connected to earth
Post by Twobarrows on Apr 28^th, 2009, 4:12pm

Lectrician wrote on Apr 28^th, 2009, 4:03pm:

Poor man's PME ?

Title: Re: neutral connected to earth
Post by speedmaster99 on Apr 28^th, 2009, 6:30pm

Wrong colours ? - it's worse than that , the earth wire is naked Cu.

I guess it has been like that for years - even since the house was built?

I know newbie, with a newbie question - but from what I can tell it is wrong yes ? ... the correct thing to do is put the wires straight then ?

Title: Re: neutral connected to earth
Post by The_Trician on Apr 28^th, 2009, 9:18pm

Yes, determine that red is live and black is neutral, and that they haven't been crossed elsewhere before they got to the box you found.
Oh, and shove some green/yellow sleeving on the bare earth wire whilst you're at it!

TT

Title: Re: neutral connected to earth
Post by speedmaster99 on Apr 28^th, 2009, 9:24pm

done

Title: Re: neutral connected to earth
Post by sparxxxx on Apr 29^th, 2009, 12:06pm

wrote on Apr 28^th, 2009, 6:30pm:

Wrong colours ? - it's worse than that , the earth wire is naked Cu.

AAAAAAAAAaaaaaaaaaaaaaaaagrh, the earth wire is naked cu, you'll be giving the sparks wet dreams, get it covered up immediately [smiley=dizzy.gif].

Title: Re: neutral connected to earth
Post by LSpark on Apr 30^th, 2009, 2:32am

All well and good, but stripey coloured clothes went out in the 60's sparxxx ;D

Title: Re: neutral connected to earth
Post by sparxxxx on May 6^th, 2009, 4:24pm

LSpark wrote on Apr 30^th, 2009, 2:32am:

stripey coloured clothes went out in the 60's sparxxx ;D

Did they? You sure? Is my sartorial elegance a delusion?

Title: Re: neutral connected to earth
Post by LS on May 8^th, 2009, 12:15pm

Each to their own I guess 8-)