Why did I not die??

[JohnW2]

Did you make the mistake of assuming that a black wire is a neutral?

If the two black wires were not neutrals then, since the L of the circuit was (presumably) 'switched off' at the CU, then I can't see how the described events could have occurred.

Kind Regards, John

 

[FrodoOne]

Hi all, I was changing a ceiling light in a very old property, the whole lighting circuit is wired in singles and in conduit, upon replacing the light fitting in the ceiling was a rather unusual set up, there were four wires in the rose, the live wire which was a single yellow for some reason?, an earth wire and 2 black neutrals? upon testing it showed no voltage

Presumably, the switch was OFF so the Yellow “Line” wire was not energised. Also (presumably) the test was made from Earth to all the other connections.

however disconnecting the neutrals I got a pretty nasty jolt.

It is probable that there was a light on that circuit turned ON in another room and the return current was traversing the Neutral connection. Breaking the Neutral connection created the potential difference.

felt a huge tingle running down my arm

Since only one arm was mentioned it seems that only one hand was being used, so the current did not flow through both arms and across the chest.
Thus, the heart was not directly affected.

Why the hell did I not die? I thought touching both live and earth or live and neutral is garanteed electrocution? My finger and thumb were on both neutrals at the time of the shock, maybe I am just lucky but Im surprised it didn't kill me or knock me off the ladder. It was quite a strong shock and cut my fingertips a little.

See the above comment.

Touching Line an Earth/Neutral will give a shock and may result in burns to the skin, which may be severe.
However, the greatest danger to life is if the current traverses the chest area and affects the heart. This would usually be via two limbs - hand to hand, hand to foot or even between to feet, as when there is a potential difference across the ground due to a nearby lightning strike.

 

[JohnD]

(presumably)

Presumably ... (presumably)

'mmmm.

 

[calumr135]

Did you make the mistake of assuming that a black wire is a neutral?

No, both black wire were connected to the neutral in the ceiling light, the live wire wire was a single yellow and a single earth wire, 4 wires in the ceiling 1 yellow (live), 1 green and yellow (earth) and 2 blacks (neutral).

I only had the light off at the lightswitch not at the consumer unit. it showed no voltage originally but after seperating the neutrals I got a belt, tested once again and there was 245v.
cheers

 

[JohnW2]

'mmmm.

What the OP has told us would make absolutely no sense (either in terms of common sense or the results of 'tests for dead' he did) if he had not first gone through the motions of switching off the (L of) the circuit concerned at his CU.

Kind Regards, John

 

[JohnD]

I don't think it would make sense if he had turned off the circuit at the CU, either.

 

[calumr135]

Does it sound like a borrowed neutral? It was certainly one of the more unusual setups I have found, I am used to seeing 3 wires in the ceiling, switch line neutral and earth, as most of the looping these days are done in the switches, at least where I live. lesson learned, whole circuit off in future.

 

[calumr135]

I have also come across the "traditional loop in method at the ceiling roses, loop in loop out and switch wire, no problems there, but I have never come across a ceiling rose like this with 4 wires, live, earth and 2 neutrals. Old properties I guess, they got up to all sorts back then I guess

 

[JohnW2]

I don't think it would make sense if he had turned off the circuit at the CU, either.

I do, if there were a shared/borrowed neutral. What aspect of what the OP described do you think would not make sense (if the circuit was turned off at the CU)?

Kind Regards, John

 

[JohnW2]

Does it sound like a borrowed neutral?

As I've said, it certainly does to me. Indeed, assuming (as all of us other than JohnD are assuming) that you turned off the circuit in question at the CU, I really can't think of any other credible explanation.

Kind Regards, John

 

[winston1]

Does it sound like a borrowed neutral? It was certainly one of the more unusual setups I have found, I am used to seeing 3 wires in the ceiling, switch line neutral and earth, as most of the looping these days are done in the switches, at least where I live. lesson learned, whole circuit off in future.

No it sounds like this from FrodoOne:

"It is probable that there was a light on that circuit turned ON in another room and the return current was traversing the Neutral connection. Breaking the Neutral connection created the potential difference."

Which is what I said in a different way back in post 5:

"I assume the yellow was a switched live and the neutrals were looped to other ceiling lights (I know you shouldn't assume, but this way is quite common with singles). Separating the neutrals would break the circuit to other lights and 240v would appear across them through the other lights."

That setup is quite common in old houses with conduit.

 

[EFLImpudence]

Have some posters missed this bit?

I only had the light off at the lightswitch not at the consumer unit.

As Frodo and Winston say.

 

[JohnW2]

Deleted - had forgotten what the OP said about wiring being in singles!

 

[JohnW2]

Have some posters missed this bit?

Yes, I certainly missed it - although most of what I've written was written long before that was posted (quite recently).

Switching off only at the light switch is obviously pretty crazy since with the 'loop at rose' system (which I imagine is easily the most common arrangement), it would leave the rose 'live'!

Kind Regards, John

 

[calumr135]

It does sound odd. Were these 'singles', one 3-core+Earth cable or two twin+earth cables - and, if the latter, what happened to the unused conductor?

Kind Regards, John

Nope, no twin and earth or 3 core and earth, just metal conduit and single wires