where do i get a neutral from for outside light

[danlightbulb]

Hi all,

I want to fit an outside light connected to my downstairs lighting circuit.

I have a switch near a door on an outside wall which controls the dining room light.

I have replaced this single switch with a double, and driled through the wall at the rear of the switch to get to the outside, near where the light will be mounted.

There is a live connection in the existing switch (obviously), but no neutral. What is the easiest way to get a neutral either into the switch, or directly to the outside light?

Thanks

 

[andy]

you have to go to the nearest light.

DO NOT take it from any sockets

 

[sparkydude]

your best way to do this is to find the existing switch cable going from your switch to your light and replacing this with a 3core and earth cable, this will give you the spare core in which to pick up a neutral from your hall lighting circuit, then just join the neutrals in the back of the switch in a connector block.

Nick

 

[danlightbulb]

Easier said than done as it is a two way light switch (other switch in kitchen).

Why can't I take the neutral from a plug socket, Andy?

Sparkydude - if I try that method, whats the chances of the cable just pulling out, with some string tied at one end, and then attaching new cable to string and pulling back through? I don't really want to lift any upstairs floorboards.

 

[Adam_151]

Why can't I take the neutral from a plug socket, Andy?

I've copied this piece on borrowed neutrals from for reference for you:

A borrowed neutral is where something (nearly always a light) has its live connection on one circuit and its neutral on another:

This is most commonly encountered with 2-way switching of a landing light. The live originates on the downstairs lighting circuit and goes through the downstairs and upstairs switches to the landing light, where of course a neutral is also needed, and the easiest place to get one is from the upstairs lighting circuit. It was done like this for years, with never a problem because people only had 1 lighting circuit. The problem arises when the lighting is split into two - Upstairs & Downstairs.

The reason it's a problem is shown below. Consider the two circuits as before, and you want to break into Circuit 2 at point X to install a new light. So you switch off the MCB, or pull the fuse, verify that the circuit is dead, and cut the cable. At that point some or all of the neutral cable in Circuit 2 becomes live via the path through the light from Circuit 1.

I submit that this is a Bad Thing™

 

[sparkydude]

No chance atall i am afraid dan. The other way is to just forget using the lighting circuit at all and install a fused spur next to a socket and then fuse down to 3amps and run the cable to the switch and then out to the light, messy and trunking involved, but SAFE

Nick

 

[danlightbulb]

Thanks guys! Think it will be the fuse spur method there is a socket nearby.

 

[danlightbulb]

Guys,

Can i just run this one by you: I'm not entirely sure about it.

All my switches are plastic switches. If the earth to the switch is a single cable that runs directly to the light, can i hijack this connection and use it to take a neutral off the light?

Its a terrible long shot I know!

 

[sparkydude]

NO in a word, lethal, unsafe, and totally against all regulations,


stick with the spur method if i were you


Nick

 

[danlightbulb]

I think in my heart of hearts i knew that was the case, but thanks.

 

[sparkydude]

No problem, thats what the forums are for, to help out people, and try to make them do it at least safeley. Make sure you sleeve the earths as a lot of diyers dont do this.

Nick

 

[andy]

use a spur from the ring main. but if you do, i dont connect it in the same switch as the lights (incase of fault)

 

[breezer]

you could even install a switched fcu, but remeber you must feed it with 2.5 t & e