Another outdoor power thread... seems the time for it!

[tom2020]

As usual – I preface this with the fact that I will be engaging the work of an electrician to do this.. however, I like to get my head around the works beforehand. This will NOT be a DIY job – I’m nowhere near skilled enough to contemplate such a thing… but with that caveat in mind – humour me please!!

I have an existing garage consumer unit, which in turn is supplied by armoured cable from the main consumer unit in the house - about 20 metres.

There is a 63A (30ma) RCD serving:

Lighting Circuit – on a 6A MCB
Power Circuit on a 25A MCB with 2 double sockets in the ‘garage’ and 2 double sockets in the ‘shed’. This appears to me to be a socket radial (?) as the furthest plug away from the consumer unit only has one cable going to it. But there appear to be three cables leaving the consumer unit. Which is odd as I thought that lights weren’t installed on a ring?? Makes more sense then that the sockets could be a ring? Or there are two separate circuits of one MCB? Don’t even know if that’s possible!?

To the problem!

I’d like to get power to the bottom end of the garden (approximately 30m) and provide 1 2gang socket half way, with the second at the bottom end of the garden. The first socket will be used very occasionally and will not be for anything more than a DAB radio or charging a phone. The second socket will be used to provide power to my soon to be installed garden railway. Both transformers are IP67 and draw 32VA each at 24v – so if my poor maths works – about 2.6A when both are in use. and will hopefully be plugged into the socket and fed through some conduit under the soil and left. I’ll house the actual controllers in a large outdoor enclosure with a flap for access.

My incessant googling has suggested that a suitably qualified spark would run armoured cable from the garage, terminate in outdoor boxes with appropriate glands and then wiring the sockets using the conductors. I think that is pretty standard – but it’s how to get power to that cable..

Would this be easier with a brand new circuit on the garage consumer unit, or would an electrician be satisfied that a spur would be the way to go? Or… and again apologies if the terminology is wrong – would, given the fairly limited use – just consider extending the existing socket radial – or would 6 be too many to comply?

Would another option be, effectively moving the last socket outside and then only needing to add one??

I hope that all makes sense – but seeing as it doesn’t really fall into emergency work – at the current time, I’m not sure whether I’d be able to get a firm quote?

Any ideas / thoughts would be very much welcome and again, I stress – this is NOT going to be a DIY job – not worth doing a rubbish job and killing someone.

Tom

 

[LewisM]

If you get somebody in who knows what they are doing then you won't have to worry about it, just pay the man and plug your stuff in.

 

[telectrix]

can spur off last socket in shed, just extending the circuit. i cover the neare half of the Wirral and would be happy to quote once the lockdown has eased off.

 

[tom2020]

Cheers both. Telectrix - will take you up on that when we know a bit more! Ta

 

[buzzlightyear]

of the Wirral and would be happy to quote once the lockdown has eased off.

I just did some work to day and will start doing work from now on. Been locked up to long Tele. Weither to day or next month it will not go away. Play safety and no one gets to die.

 

[pc1966]

Your power circuit could be a ring final circuit, or it might just be two spurs as 2.5mm cable under good conditions (not thermally insulated) can take 25A so the MCB would be OK. There has been many, many, discussions about such things here but the general consensus is they might be ugly but are not unsafe. Either way, not a problem.

If your garage unit has space for another breaker then the elegant option would be to separate the new one, but being realistic it could be fed from the same 25A breaker as you are very unlikely to need even that much all totalled up.

Best is for someone to take a look, but probably they would simply suggest extending your existing furthest socket out. As long as it is all 2.5mm wire on 25A then there is no safety issue. They should do a quick check on voltage drop though, as you should not see more than 5% drop at the end when under expected load.

This final aspect is often the reason why folk get thicker wire than expected from purely a current-carrying (thermal limit) point of view.

 

[tom2020]

Thanks for all the replies guys - I'll take Tele up on his offer!

 

[pc1966]

the terminology is wrong – would, given the fairly limited use – just consider extending the existing socket radial – or would 6 be too many to comply?

You can have as many sockets as you want, provided the total load is within the MCB and voltage drop limits.

Would another option be, effectively moving the last socket outside and then only needing to add one??

Not worth the trouble. They would need to add a junction box there and nobody here would re-use the old socket, it is much better to put in a new on that you can expect to last the warranty period!

 

[tom2020]

You can have as many sockets as you want, provided the total load is within the MCB and voltage drop limits.


Not worth the trouble. They would need to add a junction box there and nobody here would re-use the old socket, it is much better to put in a new on that you can expect to last the warranty period!

Ah - right. I get you. They're all cheapo pattress type boxes - so I assumed that whoever did the work would just replace the fascia with a fused type thing and re run the cable into the new box which would be outside... and then go from there - but makes perfect sense!! Cheers

 

[pc1966]

Ah - right. I get you. They're all cheapo pattress type boxes - so I assumed that whoever did the work would just replace the fascia with a fused type thing and re run the cable into the new box which would be outside... and then go from there - but makes perfect sense!! Cheers

The SWA cable needs a proper gland to terminate it, and they typically need a 20mm hole which you can have on the metal back-boxes and on the outdoor plastic types.

If they need to put something there for that reason then I personally would replace it with a new box and/or socket that has that size of hole but you keep the outlet there. You can (almost) never have too many proper outlets!
[automerge]1588783367[/automerge]
These are the details about the existing set-up and what you want to achieve that typically the sparky would look over when sizing up the job, but it makes only a very small difference to the overall cost to do it right.
[automerge]1588783529[/automerge]
Just to add, you don't always need Steel Wired Armour (SWA) cable, but it allows it to be directly buried if necessary and to survive a little abuse outside. If your cable run can be clipped to, say, a fence or similar all the way outside and not as such physical risk then you can use tough rubber style cables perfectly well.

 

[tom2020]

The SWA cable needs a proper gland to terminate it, and they typically need a 20mm hole which you can have on the metal back-boxes and on the outdoor plastic types.

If they need to put something there for that reason then I personally would replace it with a new box and/or socket that has that size of hole but you keep the outlet there. You can (almost) never have too many proper outlets!
[automerge]1588783367[/automerge]
These are the details about the existing set-up and what you want to achieve that typically the sparky would look over when sizing up the job, but it makes only a very small difference to the overall cost to do it right.
[automerge]1588783529[/automerge]
Just to add, you don't always need Steel Wired Armour (SWA) cable, but it allows it to be directly buried if necessary and to survive a little abuse outside. If your cable run can be clipped to, say, a fence or similar all the way outside and not as such physical risk then you can use tough rubber style cables perfectly well.

Aye - I used about a million feet of PVC conduit doing my outdoor speakers - thankfully only two colours to worry about! and about 130 less volts! I used wiska boxes and 20mm conduit - looked very tidy in the end - I'm more of a woodworker - but I'm good at drillin' holes!

Cheers for all your help - very much appreciated!