Light Ring Earthing

[rustyh]

Hi,

As Im currently doing out the lounge, I have chance to update the wiring (house wiring is 1969)

Ive already split the downstairs ring mains which was original one complete ring (including kitchen) and now have kitchen, upper and lower rings separate.

Unless told otherwise I dont think the lighting wiring needs alot of updating (although again I have split this to upper and lower rings), but the one thing it doesn't have is any earth wiring for the lighting. As the downstairs only has 3 light switches in total, and two of them are back to back with each other (the lounge and the hall), I thought it would be a good time to put in earth wiring down to each of the switches (and the light fittings).

My question is, can you just tap on to the mains ring earthing, or does it need to be a completely separate route from the CU?

Many thanks

 

[EFLImpudence]

Unless told otherwise I dont think the lighting wiring needs alot of updating (although again I have split this to upper and lower rings),

Most unlikely to be rings.

can you just tap on to the mains ring earthing,

Not ideal.

or does it need to be a completely separate route from the CU?

It really requires rewiring rather than half a job.

If not just stick to plastic switches and plastic or class 2 (double insulated) lights.

 

[Taylortwocities]

Strictly speaking, the earthing to the lighting circuits should be an integral part of the cabling.

This is the best time to rewire your lighting circuits with twin and earth cable. It sounds like you only have a small installation, and you are going to have to chop into the walls etc to get the earth wire in. Why not do it properly?

 

[rustyh]

Yeah its not a huge installation

Ive already chopped in to the wall for new socket positions and light switch positions, so this is not a problem.

So to do it properly I assume you run twin and earth (1.5mm) from CU.

Do you then send a twin and earth down to the switches with the twins being for common live and switched live, and the earth being that?

What if you have a three way switch, which switches 3 different lights individually, do you send 3 lots of twin and earth plus a common live down the channel to the switch?

 

[rustyh]

Or do you just send the send the common live, the three light lives, and a single earth cable down the channel and then link the neutrals up in a junction box on the joist

 

[EFLImpudence]

So to do it properly I assume you run twin and earth (1.5mm) from CU.

1mm² is more than adequate.

Do you then send a twin and earth down to the switches with the twins being for common live and switched live, and the earth being that?

Yes run cable light to light with switch drops.
//www.diynot.com/wiki/Electrics:Lighting-Circuit-layouts

What if you have a three way switch, which switches 3 different lights individually, do you send 3 lots of twin and earth plus a common live down the channel to the switch?

No, they are just three individual switches.

 

[rustyh]

OK, got ya

and do you loop back to the CU (as in a ring) or just a single supply from the CU as a radial?

 

[EFLImpudence]

and do you loop back to the CU (as in a ring) or just a single supply from the CU as a radial?

No. Radial circuit.