Odd Incident can anyone explain.....

[harrythehat1]

Whilst changing some taps in a groundfloor cloaks, for a client I plugged in my lead light into the nearest double socket which was under a desk in her study. The light worked fine (has a metal clamp and cage on it) by the way. As I went to reposition the light whilst touching the first of the taps I'd changed I got a belt up the left arm and the RCD operated at the CU. Reaction ouch!!.............. and Christ how did that happen......
Thinking my light was dodgy I put in the van to check later.
Client was worried about me............nice girl. As I was about to leave we spoke about it again and she asked if I'd check the double. I plugged in my M/dale and only the L/H LED lit up indicating reversed L/N. The connections were correct in the socket in question, so I then checked back to a nearby socket which it was spurred from and all connections were OK there too. It turned out the cable between the two sockets was faulty and I duly replaced it and tested it...sorted.
She'd had a telephone base station plugged into it but couldn't understand why the batteries kept go flat instead of being recharged.
My question is .............how did the shock come about?
Was it due to a break in the N and the CPC temporarily becoming a N with me touching the tap which was bonded which made the RCD open?
If the N was broken how did my light work?
Puzzled.

Cheers

Harry.

 

[JohnW2]

It turned out the cable between the two sockets was faulty and I duly replaced it and tested it...sorted.

Did you ascertain in what sense it was faulty - a broken conductor, shorts between conductors, shorts to CPC or what?

My question is .............how did the shock come about? Was it due to a break in the N and the CPC temporarily becoming a N with me touching the tap which was bonded which made the RCD open? If the N was broken how did my light work? Puzzled.

In the absence of something else being wrong (probably with your light), a broken N could/would not, per se, result in a shock, nor would your light work - hence my above question.

Plug-in testers can, in some circumstances, report a L/N reversal when the problem is, in fact, something else, particularly if something else is plugged into the same (or 'related') socket.

Kind Regards, John

 

[Spark123]

What earthing type?
Did you check ze?
Is main protective bonding in place?

 

[bernardgreen]

this is interesting. If only Live and Neutral were reversed then the Earth would still be Earth and so the cage of the hand lamp would be Earth, One has to assume the tap was earthed ( or bonded to something that was earthed )With Earth on the tap and Earth on the cage of the lamp there is no potential difference large enough to give a shock.

So was the hand lamp defective with Live on the cage or was there a potential on the tap due to some error or omission in Earthing and /or bonding of the water pipes.

 

[JohnW2]

this is interesting. If only Live and Neutral were reversed then the Earth would still be Earth and so the cage of the hand lamp would be Earth, One has to assume the tap was earthed ( or bonded to something that was earthed )With Earth on the tap and Earth on the cage of the lamp there is no potential difference large enough to give a shock.

Indeed. However, as I said a 'L/N reversal' reported by a plug-in tester does not necessarily mean what it says! It can, in particular indicate a neutral fault - but I can't see how even that, in itself, could explain what the OP experienced.

So was the hand lamp defective with Live on the cage or was there a potential on the tap due to some error or omission in Earthing and /or bonding of the water pipes.

Again, indeed. However, if either of those were the explanation (for the shock) then it would leave one having to regard it as a pure co-incidence that something was apparently wrong with the circuit/supply (as witness the abnormal tester reading), which was seemingly cured by replacing the cable to the socket. All rather odd!

Kind Regards, John

 

[harrythehat1]

The double from which the spur had been taken checked out OK with the M/dale. I initially wondered if there was an internal fault on the double which showed L/N reversed, I replaced this and the L/N reversed still showed up.
I could then only assume that there was a cable problem between the two outlets.
I trotted back home picked up some cable and returned to replace about 5m of easily accessible 2.5 and retested and all checked out fine.
As previously said the only anomaly the client had experienced was the tel. base unit not charging.
I may have had a lucky escape here given that there was a split load wylex board in the house with a functioning RCD......

Thanks for all the posts chaps.

Harry