Can’t work out what’s going on

bhamoggy · Oct 25, 2019

Old 2D light today being changed to LED.
2 black cables going to neutral and 1 red cable to live.
turned off light switch and removed old light and the 2 black cables were still live and all other lights on this circuit all knocked out. Can someone explain what’s going on

[ElectriciansForums.net] Can’t work out what’s going on

Andy5678 · Oct 25, 2019

Firstly have you followed the correct isolation procedures. What test equipment are you using?

this could be shared neutrals from other circuits

Leesparkykent · Oct 25, 2019

It’s because you haven’t carried out safe isolation. There was a load on that circuit and you disconnected the neutrals. I highly recommend you get an electrician in to do this for you as you could of got a shock or worse.

Marvo · Oct 25, 2019

bhamoggy said:
........turned off light switch and removed old light

You didn't isolate the circuit, you just turned the light out at the light switch.

The wiring that goes through that light fitting also supplies other lights elsewhere so there's current flowing through the neutrals....right up to the point where you separated them and one of them would have assumed full mains voltage.

You were lucky this time if you still have eye brows in tact, take it as a lesson and in future isolate circuits at the CU before you attempt any wiring.

edit beaten to the post by Mr Sparkykent

Dustydazzler · Oct 25, 2019

OP , can I safely assume it’s a conduit system wired in singles ?

You have a switched live and neutrals looped via the light

(Should have really isolated at the board)

littlespark · Oct 25, 2019

First (and only) time I did that as an apprentice, up steps.... How the tradesmen laughed as I flew backwards...

Seriously though... I'll repeat what others have said. You get a live reading on the neutrals from the return path of the other lights in the circuit. By separating the neutrals, there was no where for the electricity to go

buzzlightyear · Oct 25, 2019

bhamoggy said:
Can someone explain what’s going on

burned finger come to mind ,lol. and has Marvo says singed eye lashes .

MJPD29 · Oct 25, 2019

Did you take a before pic

bhamoggy · Oct 25, 2019

Dustydazzler said:
OP , can I safely assume it’s a conduit system wired in singles ?

You have a switched live and neutrals looped via the light

(Should have really isolated at the board)

Yes. Conduit system.
couldn’t work out why there was 2 neutrals and only 1 red live

westward10 · Oct 25, 2019

The circuit may have more than one switch line but a continuous neutral. You may be at the end of one switch line with the neutral looping through.

Andy78 · Oct 25, 2019

bhamoggy said:
Yes. Conduit system.
couldn’t work out why there was 2 neutrals and only 1 red live

Neutrals looped through lights and lines looped through switches ?

Surely you must know why there was voltage on the parted neutrals on a live circuit ? If not you should definitely get someone who knows what they are doing to help you.

bhamoggy · Oct 26, 2019

Andy78 said:
Neutrals looped through lights and lines looped through switches ?

Surely you must know why there was voltage on the parted neutrals on a live circuit ? If not you should definitely get someone who knows what they are doing to help you.

I’m sorry, just want to understand as I thought neutrals don’t normally carry voltage. I just want to understand why I’m seeing voltage there
Sorry for my ignorance

dmxtothemax · Oct 26, 2019

neutrals carry current NOT voltage.

Pete999 · Oct 26, 2019

bhamoggy said:
I’m sorry, just want to understand as I thought neutrals don’t normally carry voltage. I just want to understand why I’m seeing voltage there
Sorry for my ignorance

Voltage is akin to a pressure applied to conductors, it doesn't flow anywhere.

telectrix · Oct 26, 2019

the answer is that the neutrals are parted so that the L from other lights on the circuit has no return path to the installation neutral, so there is no current flow, hence no volt drop, so what was a N is now live.

Can’t work out what’s going on

bhamoggy

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Andy5678

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Leesparkykent

Marvo

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Dustydazzler

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littlespark

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buzzlightyear

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MJPD29

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bhamoggy

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westward10

Andy78

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bhamoggy

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dmxtothemax

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Pete999

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telectrix

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