Live or neutral

[Kebabs]

I wonder if someone can help me. My dad is redecorating his bedroom at the moment, and isn't sure whether it is better to run live or neutral wires directly to the light switch. He thinks its safer to run neutral wires as if he drills into them by mistake, he won't blow himself up! But I thought it would be better to find out for sure?

Thank you.

 

[Murrreid]

You need a to run a Live to the switch, then from the switch take a switch wire up into the live in the light. Take a neutral directly to the light. I don't think neutrals are allowed to be jointed in the switch box.

Correct me if I'm wrong !

 

[Murrreid]

See....

//www.diynot.com/wiki/_detail/...rics:lighting:single_way_lighting&cache=cache


Mains -

Live to loop terminations
Neutral to Neutral terminations
Earth to earth

Switch -

Live feed from loop terminations to Switch
From Switch to the live terminations on light.

 

[Kebabs]

Thanks for your help but is there any reason why it cant be the neutral?

 

[dannyboi2003]

Yes because you only EVER! put a switch to break the live connection to the light. If you switch the neutral the light fitting is still live and potentially dangerous, imagine you've put a switch on the neutral, you go to change a blown lamp assuming its safe as you have "switched it off" when changing the lamp you accidently touch the lamp holder pins and BANG!

So yes it does have to break the live and NOT the neutral, its against the regs and downright dangerous!

Also if your Dad is so worried about drilling into wires then ask yourself this, would you drill into a wall directly above, below, left or right of an electrical accessory on the wall without checking the route of the cables first? If your Dad answers yes then i suggest you take his drill off him immediately.

Sorry to sound so harsh but if you don't know what your doing when it comes to electrics then leave it to someone who does. I've only got your safety as my main priority.

 

[2scoops0406]

So yes it does have to break the live and NOT the neutral, its against the regs and downright dangerous!

I have been led to believe that switching the neutral is the preferred method in some countries eg. Spain. However I agree with the advice given, switch the live.

 

[Lectrician]

You need a to run a Live to the switch, then from the switch take a switch wire up into the live in the light. Take a neutral directly to the light. I don't think neutrals are allowed to be jointed in the switch box.

Correct me if I'm wrong !

You are corrected.

It is perfectly acceptable to join the neutrals in the switch back box.





IT IS NOT ACCEPTABLE TO SWITCH THE NEUTRAL, unless you are switching it as part of a double pole switch or similar, which is also switching the corresponding live.




Switching the neutral to prevent shock would not work anyway - With the switch off, one side of the 'neutral' will still be at mains potential via the lamp filament. It is perfectly possible to recieve a shock from an open circuit neutral.




This is another bloody good reason to never assume anything is dead or wired as it should be......you get these folk who will wire anything, anyhow.




I suspect the chap has a motoring mechanic backgroud of some sort - It is common practice to switch the NEGATIVE (not neutral) of a cars electric system. This is so that the majority of the cables, if chaffed or damaged, and short to the chassis, will simply cause the light to come on, or the horn to sound etc, rather than shorting out and relying on fuses to prevent fire.

 

[thompsk]

I wonder if someone can help me. My dad is redecorating his bedroom at the moment, and isn't sure whether it is better to run live or neutral wires directly to the light switch. He thinks its safer to run neutral wires as if he drills into them by mistake, he won't blow himself up! But I thought it would be better to find out for sure?

Thank you.

A neutral still has the potential to "blow you up" as it could be the return path from the load side back to the CU

 

[Lectrician]

Like I said

 

[Sandy Beech]

I suspect the chap has a motoring mechanic background of some sort - It is common practice to switch the NEGATIVE (not neutral) of a cars electric system. This is so that the majority of the cables, if chaffed or damaged, and short to the chassis, will simply cause the light to come on, or the horn to sound etc, rather than shorting out and relying on fuses to prevent fire.

40 years plus as an auto electrical engineer in the Motor Industry and I never knew that Vehicles are these days Negative Earth - previously they were Positive (UK) and even further back Negative. The live side was virtually always switched (there were a few but only a few exceptions and many of those actually controlled a relay which switched the live) whichever that happens to be - Viz Positive on a Negative Earth (or return) system and Negative on a Positive earth (or return) system.

 

[Click-Sure]

Looping the lighting radial through the switch is much more common than it was as people have tended to move away from having ceiling roses and towards using downlighters as it means there is no need to have hidden junction boxes (against regs btw) or 'floating' ones near one of the fittings (also against regs).

The downside is that it means using deeper back-boxes for light switches, but i've never seen that as an issue.

 

[Lectrician]

I suspect the chap has a motoring mechanic background of some sort - It is common practice to switch the NEGATIVE (not neutral) of a cars electric system. This is so that the majority of the cables, if chaffed or damaged, and short to the chassis, will simply cause the light to come on, or the horn to sound etc, rather than shorting out and relying on fuses to prevent fire.

40 years plus as an auto electrical engineer in the Motor Industry and I never knew that Vehicles are these days Negative Earth - previously they were Positive (UK) and even further back Negative. The live side was virtually always switched (there were a few but only a few exceptions and many of those actually controlled a relay which switched the live) whichever that happens to be - Viz Positive on a Negative Earth (or return) system and Negative on a Positive earth (or return) system.

Nearly all vehicles are negative earthed these days, and nearly all the switching is done in the negative. The interior courtesy light is the typical example. The main driving lights and tail lights are usually switched positives, but the rest is more commonly than not switched negative. I was taught this at college, and it has always rung true when fitting car stereos, hands free kits and alarms with central locking etc.

 

[Sandy Beech]

I suspect the chap has a motoring mechanic background of some sort - It is common practice to switch the NEGATIVE (not neutral) of a cars electric system. This is so that the majority of the cables, if chaffed or damaged, and short to the chassis, will simply cause the light to come on, or the horn to sound etc, rather than shorting out and relying on fuses to prevent fire.

40 years plus as an auto electrical engineer in the Motor Industry and I never knew that Vehicles are these days Negative Earth - previously they were Positive (UK) and even further back Negative. The live side was virtually always switched (there were a few but only a few exceptions and many of those actually controlled a relay which switched the live) whichever that happens to be - Viz Positive on a Negative Earth (or return) system and Negative on a Positive earth (or return) system.

Nearly all vehicles are negative earthed these days, and nearly all the switching is done in the negative. The interior courtesy light is the typical example. The main driving lights and tail lights are usually switched positives, but the rest is more commonly than not switched negative. I was taught this at college, and it has always rung true when fitting car stereos, hands free kits and alarms with central locking etc.

I think you will find all vehicles these days are Negative earth. I do not plan to argue the point but know a few hundred electrical and electronic engineers I served with at a major vehicle manufacturer who might take on the task. Check out some wiring diagrams in Haynes and you will see for yourself. Car stereos are fed with a positive not negative and are earthed locally to ensure minimum interference.

Note: I would never dispute your knowledge on mains stuff as I stopped playing with that more years ago than I care to remember.