Bulk Workwear - Clothing Suppliers for the Whole Forum Network
This official sponsor may provide discounts for members

Discuss Can’t work out what’s going on in the Lighting Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

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

D43232FB-49C8-4520-B63D-439DA31DA007.jpeg
 

Andy5678

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

this could be shared neutrals from other circuits
 

Leesparkykent

Mod
Mentor
Arms
Supporter
Esteemed
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

-
Mentor
Arms
Esteemed
........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 :)
 
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

-
Arms
Esteemed
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
 
  • Thread Starter Thread Starter
  • #9
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
 
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

-
Mentor
Arms
Esteemed
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.
 
  • Thread Starter Thread Starter
  • #12
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
 

Pete999

-
Arms
Esteemed
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

-
Mentor
Arms
Esteemed
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.
 
My old college lecturer said think of a shopping trolley full of shopping as your current and the person pushing it is the voltage (or something like that)
 

telectrix

-
Mentor
Arms
Esteemed
My old college lecturer said think of a shopping trolley full of shopping as your current and the person pushing it is the voltage (or something like that)
mine used to liken it to water in a pipe. the water pressure (or gravity) was the voltage, or potiential, and the water flow was the current. if you block the end of the pipe ( akin to cutting the N), then the water in the pipe has the same potential at both ends.
 

littlespark

-
Arms
Esteemed
mine used to liken it to water in a pipe. the water pressure (or gravity) was the voltage, or potiential, and the water flow was the current. if you block the end of the pipe ( akin to cutting the N), then the water in the pipe has the same potential at both ends.
But how do you make a circuit? you need to get the water back up to make pressure...
I know... a perpetual energy machine!! theres a thread on here somewhere about that...;)
 

Pete999

-
Arms
Esteemed
But how do you make a circuit? you need to get the water back up to make pressure...
I know... a perpetual energy machine!! theres a thread on here somewhere about that...;)
Recharge the battery, Put some more money in the meter, build more nuclear Power Stations.
 

BruvDunk

-
Arms
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
Probably not the best way of finding out.....
Maybe safer ways of learning than playing with un-isolated circuits...

Could of got a nasty surprise.. as mentioned before don't reconnect whilst still live...
Get the help of someone that can help sort this out for you..
 

Reply to Can’t work out what’s going on in the Lighting Forum area at ElectriciansForums.net

Instyle LED Lighting Specialists UK
This official sponsor may provide discounts for members
Electrical2Go - Online Electrical Supplier
This official sponsor may provide discounts for members
Top Bottom