Advice on installing outdoor plug

Money_Grabber13579

I'm currently looking at installing some outdoor lights in my garden.  The lights that I've chosen are low voltage, but come with a mains plug and transformer.  However, I don't currently have an outside plug and so was thinking of installing one.  Given that the sole purpose of the plug will be to power the lights, I was thinking of wiring up an outside plug socket and plugging that into an inside plug which I have in my garage.  However, I'd like to confirm whether this is an acceptable approach (if a little unconventional) and whether I'm looking at all the right components.

The outdoor socket I'm looking at is this:

https://www.screwfix.com/p/british-general-ip66-13a-2-gang-dp-weatherproof-outdoor-switched-socket/67928

As far as I understand, 2.5mm T&E cable, such as the below, should be sufficient for connecting to the outdoor socket, but would be grateful for confirmation:

https://www.screwfix.com/p/prysmian-6242y-grey-2-5mm-twin-earth-cable-10m-coil/82572

One of my main concerns is keeping the outdoor socket watertight and I think that if I insert the cable into the outdoor socket from the bottom, I need to use a gland kit to make it watertight and if I insert the cable from the back, I need to use a grommet.  Am I looking at the right parts, given the socket and cable I've chosen?

https://www.screwfix.com/p/british-general-plastic-cable-gland-kit-20mm/8797p
https://www.screwfix.com/p/mk-semi-blind-cable-entry-grommet-20mm/84115#BVQAWidgetID

I'm then proposing to wire the other end of the cable to a plug, which I would plug into the RCD adaptor below, which itself would be plugged into an inside socket (with a hole being drilled in the wall to pass the cable through):

https://www.screwfix.com/p/masterplug-13a-fused-plug-through-active-rcd-adaptor/63731?_requestid=414295#_=p

Is this an acceptable solution and have I picked out all the right parts?  I'm comfortable with wiring up the plugs, so just need some help in choosing all the right parts.

FreeBear

6242y T+E is not designed for use with plugs, nor is it really suitable for exterior use. Use a flexible cable rated for exterior use, but be mindful that it would benefit from additional mechanical protection. Is the transformer rated for exterior use ?

If not, you'd be better off keeping it inside and extending the low voltage side.

Ajmason42

What about all you need as a kit 
https://www.diy.com/departments/diall-13a-2-gang-grey-switched-rcd-socket/243629_BQ.prd

grumbler

I think a gland is unnecessary for a bottom entry.

Also, I'd use an RCD spur with a backbox instead of a plug-in adaptor and hardwire the cable.

E.g.

However, it all your sockets are RCD-protected, I think you don't need an extra RCD at all.

Section62

FreeBear said:

Is the transformer rated for exterior use ?

This^

Having a LV transformer premanently connected to an external socket doesn't sound like a great idea, even if the transformer is claimed to be weatherproof.

If possible, it would be better to have a hole through the wall that the LV cable can be passed through, keeping the mains side wholly within the garage.

If that's impossible then I'd suggest the next best would be to use a weatherproof box large enough to house the transformer, plug, and a suitable trailing socket - although the feasibility of that will depend on the amount of heat the transformer produces and whether the box allows sufficient cooling.

https://www.toolstation.com/weatherproof-box-ip54/p35429

bob_a_builder

Good example here

https://www.youtube.com/watch?v=fojd6bmNYEo&t=5s

Money_Grabber13579

FreeBear said:

6242y T+E is not designed for use with plugs, nor is it really suitable for exterior use. Use a flexible cable rated for exterior use, but be mindful that it would benefit from additional mechanical protection. Is the transformer rated for exterior use ?

If not, you'd be better off keeping it inside and extending the low voltage side.

I’m hoping not to have any of the cable outside i.e. the cable would run inside the garage, through the wall and straight into the back of the outdoor socket (so hopefully mechanical protection is less of an issue).  Would cable like this be sufficient for the purpose?

https://www.screwfix.com/p/time-3183p-black-3-core-2-5mm-flexible-cable-10m-coil/425jy

I’m actually thinking that 2.5mm cable is excessive given what it is being used for and 1.5mm would be perfectly adequate too (if not even less, but I always like to build in some spare capacity, where possible).

The transformer is rated for outdoor use and is completely sealed from the plug, to the lights, so it would be difficult to install this indoors, without cutting it somewhere, which I’m loath to do (but I will look at the possibility of doing this).

Money_Grabber13579

Section62 said:

FreeBear said:

Is the transformer rated for exterior use ?

This^

Having a LV transformer premanently connected to an external socket doesn't sound like a great idea, even if the transformer is claimed to be weatherproof.

If possible, it would be better to have a hole through the wall that the LV cable can be passed through, keeping the mains side wholly within the garage.

If that's impossible then I'd suggest the next best would be to use a weatherproof box large enough to house the transformer, plug, and a suitable trailing socket - although the feasibility of that will depend on the amount of heat the transformer produces and whether the box allows sufficient cooling.

https://www.toolstation.com/weatherproof-box-ip54/p35429

I’ll have a look at the cables again and see if there is any easy way of passing them through the wall, without having to make a fist sized hole (it’s a fairly sizeable transformer). But if I don’t have to make too big a hole, that might indeed be the easiest solution, and then fix the cable in place by filling up the gap.

Section62

Money_Grabber13579 said:

I’ll have a look at the cables again and see if there is any easy way of passing them through the wall, without having to make a fist sized hole (it’s a fairly sizeable transformer). But if I don’t have to make too big a hole, that might indeed be the easiest solution, and then fix the cable in place by filling up the gap.

Check to see if the lampholders (with the lamps removed) will pass through a smaller hole than the transformer will - if so, start inside the garage feeding the LV side outwards, rather than trying to get the transformer from outside to inside.  That's assuming there's no way the LV cable can be removed from the transformer (e.g. being sealed in due to the outdoor rating).

dil1976

Sorry but of you ar having to ask how to install it then I would advise you get a suitably competent electrician to install one for you. There is alot more than just putting a cable in and wiring one up than you think. A example being is your bonding sufficient on your install, is the circuit you are connecting to safe to connect to, is your RCD/RCBO tripping in the times it needs to. Then there is the testing of the new cable installed to ensure it is safe.

grumbler

dil1976 said:

Sorry but of you ar having to ask how to install it then I would advise you get a suitably to install one for you.

Really?

All people have to ask, read of both at some point, even a 'competent electrician' weren't burn 'competent'.  And adding a spur socket is a very simple job, especially if it's with a plug.