Neutral went bang - can someone explain this wiring to me?

[timhoward]

I'm going to start doing my own voltage testing at everything i work on as an absolute minimum.

That's exactly what I wanted to hear. It's an essential habit to get into.

We've all made early mistakes and had near misses. I once removed a fuse, tested a cable with a non-contact tester, satisfied myself it was dead and assumed I had the right circuit. After a short delay I cut into it, got a mini-jolt and blew the main fuse. It turned out to be an economy 7 storage heater feed not the sockets circuit I thought ti was and it went live at exactly the wrong moment! So many lessons in one incident there...

 

[Electrics]

OK so if it went bang properly and the sensor failed, you probably shorted the switched line to neutral and the sensor was a weaker link than the fuse. I was going to say that 'bang' was a bit of an exaggeration for just breaking a loaded lighting circuit.

Could it be that the newly detached neutral wire contacted the switched line terminal or an exposed section of the conductor as you moved it away from the terminal?

Yes definitely could have been, all the wires were cut really short so were quite close together.

It literally made a small bang noise, some blue flashing.

I still don't really understand how because the line in was off at the emergency switch. I'll watch John Ward's video since if i see a diagram i'll get it. If not expect a diagram from me soon!

 

[Electrics]

That's exactly what I wanted to hear. It's an essential habit to get into.

We've all made early mistakes and had near misses. I once removed a fuse, tested a cable with a non-contact tester, satisfied myself it was dead and assumed I had the right circuit. After a short delay I cut into it, got a mini-jolt and blew the main fuse. It turned out to be an economy 7 storage heater feed not the sockets circuit I thought ti was and it went live at exactly the wrong moment! So many lessons in one incident there...

Thanks for not roasting me! To be fair he's turned off about 10 lights for me and they all went in without a hitch so i didn't expect it, but it's a very valuable lesson to get in my first week. I think because i'm older and can already do the basics they might take less care with me so i'll have to take it into my own hands. It's a business that was open at the time so i guess it's easier to isolate at the emergency test switch than at the board and knock a load of their lights out while it's full of customers. Still, health and safety comes first. No good learning some stuff and earning money if i don't go home safely.

As a side, i'm going to write another thread about my experience and how my mindset was before this first week on the job. Think it would be helpful for anyone wanting to try a shorter route into the industry since it's a fairly brutal reality.

 

[Petej999]

I think that's what he hinted at but we were running round like blue arsed flies trying to finish so he didn't have time to explain properly.

Isn't shared neutrals bad?

Very bad at times

 

[mattg4321]

If you’re not turning of MCB’s when you’re changing lights then even if you’re not touch ‘live’ (I mean line) parts/terminals you can still get a shock from the neutral. It’s especially true when working on systems wired in singles.

Often with singles wiring you won’t have a permanent line conductor at a light fitting. Testing with your voltage indicator will show its all dead… UNTIL… you disconnect the neutral that is looped through the light fitting being worked on. You now have a floating neutral that rises to line voltage. Turn off the damn MCB!

 

[Electrics]

If you’re not turning of MCB’s when you’re changing lights then even if you’re not touch ‘live’ (I mean line) parts/terminals you can still get a shock from the neutral. It’s especially true when working on systems wired in singles.

Often with singles wiring you won’t have a permanent line conductor at a light fitting. Testing with your voltage indicator will show its all dead… UNTIL… you disconnect the neutral that is looped through the light fitting being worked on. You now have a floating neutral that rises to line voltage. Turn off the damn MCB!

Could you please explain what looping is? I've looked it up and I'm a bit lost.

 

[Dave OCD]

It's just when a conductor is connected in the same terminal from fitting to fitting , simple as that really.

 

[Vortigern]

A shared neutral is perfectly normal and required within a circuit. A borrowed neutral is a no no as it is from another circuit. When you took the neutral out did you notice lights going off elsewhere?

 

[nicebutdim]

I'm on a trial for a potential apprenticeship and don't want to put a spanner in the works because it's going well but i also quite like being not dead.

Fingers crossed it works out for you.

I'm loving every minute of it and wishing I'd made the move years before.

 

[Electrics]

Fingers crossed it works out for you.

I'm loving every minute of it and wishing I'd made the move years before.

Yeah it's been graft, i started short notice on Saturday and did 65 hours this week, with a couple of late night finishes. I'm glad to be getting stuck in again after essentially being a stay at home dad for the past 5 years.

Here's hoping we smash it pal.