Never seen this before............

C

Crosswire

Went to a house today where outside lights were tripping the rcd.

1.5 swa from house to ip box containing timer, which controlled a few sets of lights - wall lights, light in bin store, and drive over lights.

Each group of lights had one cable from ip box , all fairly standard stuff.

Anyway split all lights apart and touch them on one by one to live feed to find faulty lights quickly ( was the drive over lights full of water, but this is not the point) .When I touched the wall light on I got a belt off the neutral which was hanging loose and brushed my hand !

Seperated cable and found it did ONE wall light (230v ES).
When lamp was put in got 230v on neutral .
Tried three different testers all showed 230v
Meggered cables all perfect readings
Connected this light on it's own to feed and energised - didn't trip breaker or RCD and light worked fine!
Went to board tested neutral and earth bars - 0 v.

It was my understanding that the resistance of the lamp should cause the voltage to drop to 0v across the load, and the neutral should be a return path for current, not voltage!

Anyone explain this ?

*Disclaimer * Please no-one post about 'safe isolation procedure' etc.. I know what I did is not textbook, but it is QUICK. The point of this thread is the strange voltage on the neutral, and nothing else. Cheers!
 
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Crosswire said:
Went to a house today where outside lights were tripping the rcd.

1.5 swa from house to ip box containing timer, which controlled a few sets of lights - wall lights, light in bin store, and drive over lights.

Each group of lights had one cable from ip box , all fairly standard stuff.

Anyway split all lights apart and touch them on one by one to live feed to find faulty lights quickly ( was the drive over lights full of water, but this is not the point) .When I touched the wall light on I got a belt off the neutral which was hanging loose and brushed my hand !

Seperated cable and found it did ONE wall light (230v ES).
When lamp was put in got 230v on neutral .
Tried three different testers all showed 230v
Meggered cables all perfect readings
Connected this light on it's own to feed and energised - didn't trip breaker or RCD and light worked fine!
Went to board tested neutral and earth bars - 0 v.

It was my understanding that the resistance of the lamp should cause the voltage to drop to 0v across the load, and the neutral should be a return path for current, not voltage!

Anyone explain this ?

*Disclaimer * Please no-one post about 'safe isolation procedure' etc.. I know what I did is not textbook, but it is QUICK. The point of this thread is the strange voltage on the neutral, and nothing else. Cheers!
Click to expand...

But the 'neutral' wasn't a 'neutral' while it was disconnected, was it?
 
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if the neutral is not connected back to the cu, then there is no current flow throughn the lamp. therefore there is no volt drop across the lamp. therefore the neutral is sitting at 230volts. ssssimples.
 
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telectrix said:
if the neutral is not connected back to the cu, then there is no current flow throughn the lamp. therefore there is no volt drop across the lamp. therefore the neutral is sitting at 230volts. ssssimples.
Click to expand...

Ah of course! Now I understand................LOL

Thanks for enlightening me :)
 
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What your describing is not that far from a shared neutral scenario. Same result !! You get a belt. Always treat neutrals with the same respect you treat a live conductor. You live longer that way. :devilish:
 
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davelerave said:
it is a live conductor
Click to expand...

I would say a neutral is a neutral.
It can be at the same potential as a live, I agree there, but its a return after the load, and its voltage is dependant on the resistence of that load.
Thats why you treat it with the same respect.
A corpse aint gonna argue either way.
 
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As far as danger goes,the word "neutral" portrays a laid back feeling and no issues

Now if we had a supply that was Three phase and Nasty neutral,the message changes
icon12.png
icon14.png
 
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davelerave said:
ya it's just a technical term

live conductor-'conductor forming part of a circuit'

people refer to the phase/line as 'the live' regardless
Click to expand...

True enough Dave, True enough.

And when some less experienced,or been working a long day sparky chap touches that phase,line,nuetral,thingy, whatsit, that forms part of the circuit.
They come out with a few technical terms of there own, lol.
 
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It also got me a few years ago. It reminds me of a question i once got in a C&G exam years ago.

How many current carrying conductors are there in a ring final circuit?

Cheers.........Howard
 
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SirKit Breaker said:
It also got me a few years ago. It reminds me of a question i once got in a C&G exam years ago.

How many current carrying conductors are there in a ring final circuit?

Cheers.........Howard
Click to expand...

that depends if there's earth leakage present. if there is, then the cpc is a current carrying conductor.
 
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Awww....spoilsport:35:...........

Seriously though, you choose your own way of doing things and best of luck.But I thought the point should be made,bearing in mind this is on the open forum,and those with less skills than yourself may try and use the 'method' to find a fault...with possibly fatal consequences......Thats all.
 
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wirepuller said:
Awww....spoilsport:35:...........

Seriously though, you choose your own way of doing things and best of luck.But I thought the point should be made,bearing in mind this is on the open forum,and those with less skills than yourself may try and use the 'method' to find a fault...with possibly fatal consequences......Thats all.
Click to expand...


Ok fair enough..

"Under no circumstances should anyone but the foolhardy or the terminally depressed copy my 'method'. "




Luckily I fall into both both categories.:goofy:
 
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And don't think the cpc or earth thingy whatever you want to call it is an innocent party in all this, its not.
I remember well the results on a pme system, sorry TNC-S thingy whatever. When the main earthing terminal had been lost at the mains position. It was an industrial install with lots of galv, conduit, trunking, and metalclad switching sockets ect, ect. I thought isolate the mains son, quick. Of course the switchfuse was also metalclad, SH#T, BO####S, OWCH!
 
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