Neutral.

[gerry.slater65@]

Could someone please explain to me in VERY SIMPLE terms what is meant by a borrowed neutral? (or is it shared??).
I see it mentioned quite a bit but can't understand how it happens or it's implications.

Thanks in advance,

Gerry

 

[Mac]

It has been borrowed off another circuit,as you said,it is shared.

 

[gerry.slater65@]

Cheers Mac, but could I have a little bit more?

When,where why and how does it happen and what are the ramifications.

You never know, I might let you look at my Arsenal season ticket!

 

[Mac]

The most likely instance where you will find a borrowed neutral is the hall/landing light circuit with a two way switch which enables you to switch on the light from the bottom or top of the staircase.
Domestic lighting is usually split into an upstairs and downstairs circuit each with it's own breaker being a fuse or MCB. Now when the house was rewired back in the 80's a not very scrupulous electrician (but following what was very common bad practice) decided he could save himself a bit of time and cable when wiring the landing light. He used the live red wire from the downstairs light circuit to provide the supply to the downstairs light switch, which was wired in with the upstairs light switch in two way configuration. So the live supply to the landing light upstairs was from the downstairs light circuit.
But, he also needed a neutral supply to the upstairs landing light and what could be more easy than running an neutral to this light from the upstairs light circuit. He thinks this is no problem because all neutrals are connected together back at the fuse board anyway. Electrically the circuit will work.
Now, assume you have this arrangement and you decide to fit a new light fitting in the bedroom and pull the fuse on the upstairs lighting circuit (or switch off the MCB). You carry out a voltage test on the ceiling light that you are about to disconnect and happy that the circuit is dead you continue to disconnect the wires from the ceiling rose. Whilst wiring up your new light somebody in the house comes up the stairs and turns the staircase light on. Bang! Your dead.
The reason, because of the borrowed neutral. When the landing light which was on the downstairs circuit is switched on and you were working on the upstairs, this current flowed through the light bulb and into the upstairs neutral circuit. Whilst the neutrals on your upstairs fitting were connected together they were at neutral potential. When you took the neutrals out of the terminal block the one that went back to the landing light became live because it was connected through the light bulb to live supply. When you touched it the current that would have flowed through the neutral circuit back to the main neutral at the fuse board is now trying to flow through you to ground.
Electricians have been killed as a result of borrowed neutrals so be advised, the best solution is to switch off at the main switch.Can i see your season ticket now please

 

[gerry.slater65@]

Nice one Mac!

I don't think that a Spud would have been afforded such a comprehensive reply.

If you struggle for tickets, PM me, I will see what I can do.

If not thanks again mate.

Gerry

 

[Mac]

Cheers mate.Haven't been to a game in ages.I may take you up on that offer.Thanks

 

[Notsosmart]

The most likely instance where you will find a borrowed neutral is the hall/landing light circuit with a two way switch which enables you to switch on the light from the bottom or top of the staircase.
Domestic lighting is usually split into an upstairs and downstairs circuit each with it's own breaker being a fuse or MCB. Now when the house was rewired back in the 80's a not very scrupulous electrician (but following what was very common bad practice) decided he could save himself a bit of time and cable when wiring the landing light. He used the live red wire from the downstairs light circuit to provide the supply to the downstairs light switch, which was wired in with the upstairs light switch in two way configuration. So the live supply to the landing light upstairs was from the downstairs light circuit.
But, he also needed a neutral supply to the upstairs landing light and what could be more easy than running an neutral to this light from the upstairs light circuit. He thinks this is no problem because all neutrals are connected together back at the fuse board anyway. Electrically the circuit will work.
Now, assume you have this arrangement and you decide to fit a new light fitting in the bedroom and pull the fuse on the upstairs lighting circuit (or switch off the MCB). You carry out a voltage test on the ceiling light that you are about to disconnect and happy that the circuit is dead you continue to disconnect the wires from the ceiling rose. Whilst wiring up your new light somebody in the house comes up the stairs and turns the staircase light on. Bang! Your dead.
The reason, because of the borrowed neutral. When the landing light which was on the downstairs circuit is switched on and you were working on the upstairs, this current flowed through the light bulb and into the upstairs neutral circuit. Whilst the neutrals on your upstairs fitting were connected together they were at neutral potential. When you took the neutrals out of the terminal block the one that went back to the landing light became live because it was connected through the light bulb to live supply. When you touched it the current that would have flowed through the neutral circuit back to the main neutral at the fuse board is now trying to flow through you to ground.
Electricians have been killed as a result of borrowed neutrals so be advised, the best solution is to switch off at the main switch.Can i see your season ticket now please

Wow the most comprehensive reply I've seen you post to date

Course nothing to do with gooner favouritism or the bribery

Good post mate.

 

[Mac]

Wow the most comprehensive reply I've seen you post to date

Course nothing to do with gooner favouritism or the bribery

Good post mate.

Ha Ha mate