Wiring outside light off existing extractor fan supply.

[Electrics]

Friend of mine has an existing extractor in the bathroom which is switch powered. He wants to disconnect it as it's never used, and feed a cable from the existing extractor feed through the exterior wall and into a PIR exterior light.

He's insisting that regular 1.5mm pvc is fine (i've said it isn't) and that the fact it's not earthed is fine (i'm pretty sure nowadays everything has to be earthed regardless of its material??)

I think he should connect up in 1.5mm, something like rubber (don't think SWA is necessary as it's up high and will never be touched) and join in the earth from the existing supply.

Thoughts?

(I wanted to put this in DIY but wasn't allowed.)

 

[DefyG]

Cable size is fine (domestic lighting generally 1.00/1.50 sqmm).
Some external flood lights are Class 2 / Double insulated and therefore do not require and earth termination.
However!
The supply cable should incorporate an earth conductor (cpc), the centre uninsulated conductor of a flat PVC twin&earth cable.
There is a bit of a loop hole though where installations (early 60's I think) did not incorporate a cpc in the lighting cable and this is deemed ok as long as no class 1 fittings (Lights and switch plates) are installed!
A label indicating this should be attached to the consumer unit.
The connection, if inaccessible should be made using a maintenance free junction box and I would probably recommend using one in any case as virtually foolproof.
Domestic lighting should also have RCD protection.
The alteration, depending upon where within the bathroom could also be subject to notification (Building Regulation Part P) and will require formal testing/certification (Minor Works).

 

[Electrics]

Thanks for the response. What about cable type? I don't think there will be too much cable on display but obviously normal PVC twin and earth will just degrade over time and he doesn't want to put anything in trunking.

I was thinking rubber since 12 inches of SWA seems a bit overkill considering it's up on a facia board and shielded from both people and weather.

 

[DefyG]

Most domestic LED flood lights come pre-flexed so probably best to run PVC T&E straight through the wall to a external junction box and gland the flex into this.

 

[Electrics]

Most domestic LED flood lights come pre-flexed so probably best to run PVC T&E straight through the wall to a external junction box and gland the flex into this.

This one is bare, but has a plastic glanding for the feed into the light. What would you recommend?

Just FYI, i'm not doing this job nor advising him, just curious as he knew i was interested in electrics and asked me and i haven't a clue, so this is all info for my own knowledge bank.

 

[Ziggie]

You didn’t mention if the existing feed is RCD protected already. The extractor fan might have a junction box in the bathroom which may fall within the zone system depending on distance from the bath/shower. Proximity to the shower/ bath introduces constraints as does running the cable through the bathroom space. I can supply additional information if this is the case.

Assuming no junction box or cable in the bathroom ( proximity to bath/shower) I think if the outside light lies against the wall and provides a connection box built in then normal flex would be fine.

 

[Electrics]

You didn’t mention if the existing feed is RCD protected already. The extractor fan might have a junction box in the bathroom which may fall within the zone system depending on distance from the bath/shower. Proximity to the shower/ bath introduces constraints as does running the cable through the bathroom space. I can supply additional information if this is the case.

Assuming no junction box or cable in the bathroom ( proximity to bath/shower) I think if the outside light lies against the wall and provides a connection box built in then normal flex would be fine.

It's RCD protected at the CU, fed by junction box in the ceiling space but directly above the toilet, so as far from the bath as you can get. The run would go about 12 inches through the facia outside and then straight into the light.

The light is gonna be directly on the facia right where the cable exits and so there will be very little of it outside anyway.

 

[littlespark]

Most floodlights that don’t come preflexed say not to use t&e- must be round cable, so either joint box outside or enough flex to go inside and joint there.

just a question about the fan.... I know it doesn’t get used, but would removing it cause problems re condensation.

 

[Dartlec]

This one is bare, but has a plastic glanding for the feed into the light. What would you recommend?

Just FYI, i'm not doing this job nor advising him, just curious as he knew i was interested in electrics and asked me and i haven't a clue, so this is all info for my own knowledge bank.

Twin and Earth isn't suitable for exposure outside, due to UV light and cold degrading the insulation. Having said that, I've seen houses with T&E that's 30 years old outside and it still hasn't given up, but that's not an excuse for not doing it right now.

One option might be to take the T&E through the wall directly into the back of an IP rated box, which then has flex to the light. Makes it a lot easier when having to change it in a few years because they don't make them to last....

1.0mm or 1.5mm flex (preferably black) should be fine - rubber better. But it has to be suitable for the fitting, since the gland that comes with it will need to make a good grip on the cable to avoid moisture running into the fitting. A drip loop on the feed flex is a very good idea.

Part P shouldn't be an issue if the junction box is up in the ceiling - flex from that straight out the wall is another option, but the external box makes replacement easier in my experience.

I'd be surprised if there isn't an cpc already to the fan feed, unless it's very old wiring, but it's possible that it wasn't connected to the fan since most fans are Class 2.