Outside lights

We had our flat rewired a couple of years ago, and we had the electrician install a connection to allow us to fit outdoor lighting on our third floor terrace at a later date (and they left us some SWA cable, grey/black/brown).

They fitted a light switch that runs to a backbox on the internal/room side of the external wall to the terrace, inside the box is a simple electrical connector where the internal wiring (blue/brown/earth) ends and a blank face plate covering the box.

We now have finally got around around to wanting to install the outdoors lights, and wondering what to do. I never really thought about it until now, and just took the cable from the electrician in thanks at the time.

We have purchased two external lights that are mains powered. The lights are dimmable (as is the switch in the room):
https://www.amazon.co.uk/Philips-myGarden-Bustan-Pedestal-Bulb/dp/B06WWHXHK7/

Is it necessary to run SWA cable to these, and if so how do I terminate SWA into a standard backbox? and ditto into the light fitting?

The install manual for the lights doesn't really give much information - it looks like the cable simply goes up through the base of the fitting, and the fitting is then sealed in itself once assembled.

The cable runs will be about 2m and 4m and not buried in soil, they will be loose laid under decking on the terrace.

Any help much appreciated.

There are a number of ways to move from flex to SWA, one is the conduit box, SWA gland one end, stuffing gland other end, and fill the box with something which will stop water getting in, re-enter-able compound of some sort, could be petroleum jelly, the metal socket back box again you can use SWA glands in the knock outs. There are three ways to deal with water ingress, one is seal the unit, the other is have holes so water can drain, and other is leave no space for water.

As the installer you have to consider which is best, epoxy resin cable joints, are another option, where I live in Wales this is notifiable work, so the cost to use the LABC route is £100 plus vat, could be more if the LABC wants to use third party inspectors, so in Wales cheaper to use a scheme member electrician, England and Scotland have different rules, but also the regulations have changed so now all is RCD protected, outside lights are a problem, as a little water can result in other items in the house also to stop working, so double pole switching or isolators are normally used so you can switch it off if faulty so will not effect rest of house.

It may be better not to DIY in this case.

Are you proposing I add another connection box externally?

I thought the connection between the flex and SWA could simply be made in the existing box that is inside the building - where no water should be getting in. With the SWA cable then being sealed as it passes through the wall (with the hole also being drilled at a slope outwards to stop water trickling inwards).

If the connection is wholly internally does it need glands and sealing - I'd hoped it would be treated as a simpler internal connection straight onto the connector and using SWA was simply to help protect against weathering/damage to the outside cable. Or can an SWA simply never be used like that?

Instead could/should I simply be using weather resistant flex? like this:
https://www.toolstation.com/pitacs-weather-resistant-rubber-pond-flex-cable-3183p/p17796

External works don't look to be notifiable in domestic works in England unless adding an extra circuit. To be honest I was quite surprised by this.

lt8480 said:

Is it necessary to run SWA cable to these,

Click to expand...

Probably not.

lt8480 said:

Are you proposing I add another connection box externally?

I thought the connection between the flex and SWA could simply be made in the existing box that is inside the building - where no water should be getting in. With the SWA cable then being sealed as it passes through the wall (with the hole also being drilled at a slope outwards to stop water trickling inwards).

If the connection is wholly internally does it need glands and sealing - I'd hoped it would be treated as a simpler internal connection straight onto the connector and using SWA was simply to help protect against weathering/damage to the outside cable. Or can an SWA simply never be used like that?

Instead could/should I simply be using weather resistant flex? like this:
https://www.toolstation.com/pitacs-weather-resistant-rubber-pond-flex-cable-3183p/p17796

External works don't look to be notifiable in domestic works in England unless adding an extra circuit. To be honest I was quite surprised by this.

Click to expand...

Addition to a circuit needs a Minor works cert

These works don't appear to be notifiable under Part P of the Building regulations (Part P - 2.5, 2.7, 3.1). Is the requirement for a MWC covered by BS 7671 (under Part P section 3.13 requirements) somewhere?

The Minor Works Certificate has nothing to do with Part P of the Building Regs or BS8621. It is a requirement for compliance with BS7671, the Wiring Regulations (which is is not, in itself, a legal requirement). BS8621 is a standard for locks

Part P does not have a section 3.13:

https://www.diynot.com/wiki/Electricsart_p:Statutory-Instrument

Edit: I see you have corrected the BS #

Indeed it should have said BS 7671 (could have swore I copied the ref from Part P - I must have mis typed).

Attached is section 3.13 I was referring to.


Do you know the section in the BS that relates so I can see what I need to get done.

Thanks.

This is Part P of The Building Regulations:



That's it. There is no more.

Anything else you read is just something someone else has written.


It's only been sixteen years since it was introduced.

Yes I was referring to the AD which is not technically the BRegs Part P requirement, and I appreciate the AD isn't the only way of complying with Part P; but in lieu of not complying with the Approved Documents that follows the Part P requirement, usually the alternative is to follow BS requirements as "Reasonable provision" - which is basically where we have ended up anyway. Unless you are suggesting there is something else I can follow?

The usual method of compliance with Part P is to comply with BS7671.
BS7671 requires that an appropriate certificate is completed for all electrical work.

The vast majority of electrical work in England isn't notifiable. Only replacement consumer units, new circuits and work within the zones of a bathroom are.

There is no requirement to use SWA for outside lights, or any other situation.
Cables must be suitable for the environment they are installed in.