Ask The Trades - neutral connected to earth

speedmaster99

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neutral connected to earth
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?

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speedmaster99 GDPR opt-out	Re: neutral connected to earth Reply #1 - 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
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scotspark Trade Member Offline mmmmm it's gonna cost you!! Posts: 3074 Total Thanks: 10 For This Post: 0 scotland Scotland Gender: Trade: Electrician	Re: neutral connected to earth Reply #2 - Apr 27^th, 2009, 12:37am could still be tncs
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Lectrician

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Re: neutral connected to earth
Reply #3 - 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.

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CWatters Super Member Offline "Daddy fick it" says James Posts: 5150 Total Thanks: 58 For This Post: 0 Gender:	Re: neutral connected to earth Reply #4 - 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.
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speedmaster99

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Re: neutral connected to earth
Reply #5 - 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

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Y3 GDPR opt-out Total Thanks: 58 For This Post: 0	Re: neutral connected to earth Reply #6 - Apr 27^th, 2009, 8:23pm When u isolated the circuit, was it the whole consumer unit or just the fuse?
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speedmaster99

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Re: neutral connected to earth
Reply #7 - 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.

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Lectrician Administrator Trade Member Author Offline Ask The Trades Posts: 8815 Total Thanks: 109 For This Post: 0 Braunton, North Devon United Kingdom Gender: Trade: Electrician	Re: neutral connected to earth Reply #8 - Apr 27^th, 2009, 9:18pm Earth and neutral crossed
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CWatters Super Member Offline "Daddy fick it" says James Posts: 5150 Total Thanks: 58 For This Post: 0 Gender:	Re: neutral connected to earth Reply #9 - 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
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speedmaster99 GDPR opt-out Total Thanks: 58 For This Post: 0	Re: neutral connected to earth Reply #10 - 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 ?
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Lectrician Administrator Trade Member Author Offline Ask The Trades Posts: 8815 Total Thanks: 109 For This Post: 0 Braunton, North Devon United Kingdom Gender: Trade: Electrician	Re: neutral connected to earth Reply #11 - 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.
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Twobarrows

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Re: neutral connected to earth
Reply #12 - Apr 28^th, 2009, 4:12pm

Lectrician wrote 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.

Poor man's PME ?

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speedmaster99 GDPR opt-out Total Thanks: 109 For This Post: 0	Re: neutral connected to earth Reply #13 - 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 ?
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The_Trician Trade Member Offline Posts: 7721 Total Thanks: 8 For This Post: 0 Gender: Trade: Electrician	Re: neutral connected to earth Reply #14 - 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
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speedmaster99 GDPR opt-out Total Thanks: 8 For This Post: 0	Re: neutral connected to earth Reply #15 - Apr 28^th, 2009, 9:24pm done
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sparxxxx Full Member Offline Posts: 435 Total Thanks: 0 For This Post: 0	Re: neutral connected to earth Reply #16 - Apr 29^th, 2009, 12:06pm Quote: 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 .
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