Education ATTN Sparkies - Electrical Advice - Running Power to outbuildings

Hi chaps,

I'm building a shed in the back garden to house my Lathe and other machine tools I plan on getting later on. Obviously this will all need power.

I need some advice on the best way to run the cabling to the shed.

Here's a rough, not to scale layout of the house and the sheds:



The main consumer unit is in the garage.

My initial thought is it would be easier and cheaper to take a feed from the consumer unit out of the garage wall and then straight up to the loft, with the cable in some galvanized conduit. Then run the cable through the loft to the opposite wall and then down toward the sheds in more conduit, with the main feed ending up in the workshop and a separate small consumer unit there.

Here it would feed 4-5 double 13amp sockets and some fluorescent lighting, and some form of light in the shed down the side of the house.

What I need to know is would this be OK by the electrical regs?

I know this sort of thing is notifiable to the powers that be, so it would have to be signed off by a qualified professional - but how much of it can I do my self, and what needs to be left to the Sparkie?

I've tried researching this myself, but get lost with earthing methods, cable cross section, separate earths, Part P and voltage drops.

Other things - the Lathe is 1000w, 13amp. Any other machine tools would be of similar rating, but unlikely that they would be run at the same time. An outside socket on the wall of the workshop would be nice for the lawn mower.

Thanks In Advance,

GOO

 

Disclaimer:- I'm not a sparkie.

IIRC, you can do all the work yourself except the hookup to the consumer unit.
That needs to be done by a pro, but it would be best to have him look over what you do yourself while he's there.

 

You can do it all yourself but it would have to be checked over by a spark and certified before it would be legal. I am assuming that as your asking on here you don't know a friendly sparky so you may have problems finding someone willing to sign it off for you.

The other option is to run the cable yourself to the points you want sockets, mount the boxes but have the spark do all the connections for you. For the connection to your shed you will need to run armored cable and standard practice is to bury this underground. In your shed you would have a small consumer unit to isolate the supply from your house and run your circuits from there.

To clarify i'm not a spark either but I have recently gone through a complete rewire and running power out to a garage. Wiring is pretty easy, but as you've said working out what you need isn't and I think we underestimate what sparky's do in this country. I would get some quotes and discuss what you need and what you can do yourself with a proffesional. What your describing sounds like an afternoons work at the most to me.

 

I'd run a nice, thick cable from a dedicated socket to a simple rcd in the shed, then take from there what you need, i.e. lighting, sockets. It depends how many circuits you want in the shed I guess. You could have an rcd for each, it'd just be a case of wiring up whatever you want to trip off whichever rcd from the main 'feed'/cable into the shed.

I'd agree with IanW. You probably could do the wiring job yourself if you wanted it to come off the consumer unit and then get it inspected for insurance purposes, but I'm unsure on that score tbh. I use a nice, thick, bright orange caravan charging cable to supply a feed to my shed. It has run garden lighting, a lawnmower and a pond pump without incident.

 

Completely off topic, but the first four posts in this thread represent nearly 40 combined years of Bit-tech membership!

 

I can't help much with the wiring aspect to it but I will add that it might be worth you looking into keeping a spare way on the workshop board available for a hard wired surge protection device especially if you are going to be running any electrical welding equipment or a machine with a substantial motor on it.

You wouldn't need anything with a massive kA surge rating (something like 40kA 8/20us should be fine) but it would be a good idea to look at something that gives a decent, low let through voltage (Around 600v is considered decent). By fitting it to a spare outgoing way of the board it will ensure that any surges originating from inside the workshop are dumped to earth at the board and also any surges coming in on the supply will also be diverted before they get into equipment.

A surge unit like this will also protect to some degree from lightning induced surges, especially in a domestic situation where the surge currents are likely to be a bit lower than a large industrial site.

Oh, and shirty, here's another 10 years to add onto your tally

 

The law is you get a certified person to do it for you who can sign off the work, issue you with the certificate to say it's done correctly and who will notify building control for you. Or you can do it yourself, notify the building regs dept and supply them with a plan of work. If they agree to it they will notify you of the requirements and inspect the work either during install and/or once its completed and if it meets the required standards they will issue the certificate. You may save the cost of the sparky but you will have a lot of hassle, will need time off work for the inspections and the project will progress at the speed of your local authority building control. Are the savings worth the hassle and the cost in your time?

Or you can just do it yourself and ignore the law but that will invalidate your home insurance and will bite you on the arse if you sell your house. It's one of these UK laws which is supposed to stop cowboys and incompetent DIY'rs causing accidents but only causes hassle for those who play by the rules.

 

I'd echo much of the above, based on my Dad's shed hookup in the past; in other words:

1. You can run all the cable physically yourself both within the shed and from your garage to the shed.

2. You'll need a sparky to connect it in at the consumer unit, and at the sockets (as above you can pull the wires though, it'll save you lots of dosh).

3. Make sure the cable you run is rated to the amps/watts you intend to draw over it.

4. My Dad had to have a seperate fuse box in the shed, essentially a new ring for the shed, and then the sockets all go back to individual fuses in a smaller fuse box. I guess it'd be sensible for this to be RCD these days, especially if you wanted an outdoor socket which I'd suggest should be on its own RCD, even if you bunch the rest together.

 

This is a conspiracy. 70 years in 7 posts...

One thing I have learned is that ~10 years Bit-tech membership makes one a minor authority in household electronics.

 

We're men, its what we do!

 

If you are going to bury the cable in the garden does it not have to be at a certain depth with a warning tape / net buried between that and the surface to warn anyone digging there that there is a cable x meters below the warning? Or am I thinking more on a larger scale?

Also would it need updating on any plans?

Finally, old members post count +9ish.

 

Underground wiring isn't that bad, yes you need to run tape above the cable but depth depends on what's above it.

http://www.tlc-direct.co.uk/Book/7.13.3.htm

If you could run it above ground it's a lot easier as there no digging involved, just needs to go in a suitable conduit.

 

It's more the 5 years designing lightning conductors and surge protection systems for me but yeah, we do certainly have a lot of amateur sparkies on here. I guess it kinda goes with the territory.

 

And that's the reason I would like it not to go round the garden - not just the expense of armored cable, but getting a suitable depth would be hell - We have a bout 10 to 12" of top soil, and then you're down onto bed rock.

Hence my idea of up the wall in conduit, through the loft and then down the opposite wall in similar conduit to the sheds. I can run the cabling between the sheds pretty easily, as there is a trellis / pergola between the sheds, so conduit can be run above head height there, attached to the frame work - And it'll be hidden by the honeysuckle & clematis plants that grow over it.

 

You wouldn't need conduit indoors, standard plastic trunking would be fine

Certainly a bonus if you can run it round using the fence/trellis, that'll save a lot of time.

 

Ah, no - not inside. Up the outside of the wall.

If I start channeling walls for cable, Mrs GOO will not be pleased. She still hasn't forgiven me for knocking holes in the wall to run my speaker cables in the front room... And that was nearly 10 years ago...

 

Ohhhh, certainly don't want the wrath of the Mrs after she's agreed to let you have a man cave workshop in the first place

 

I did this at my student house and did most of the wiring myself with the help and permission of my friend, the house owner. We were reconnecting and adding power outlets and lighting to the garage that I ran my folding rigs in whilst I was living there. Everything that you've been told so far is correct. If you have a friend who's a certified spark or a friendly local electrician who can look over it for you and sign off on it, go for it. I also wired my own workshop here and had a friend of mine who's an electrician (and taught me most of what I know about the trade!) check and sign off on it.

To get power outside we used an armoured weatherproof cable that was just run overhead between the wall of the house and the corner of the garage. That particular installation wasn't signed off on in my time living there, but as far as I understand it, as long as the type of cable used is correct and it's securely attached to both buildings, it's fine to do so. That was spanning a small distance of 3 or 4 feet though, and anything farther from the house like you're dealing with will require an armoured underground cable with the necessary tape over the top of the cable.

Chalk up another 7 years of membership - and about 10 years of doing "stuff" with electricity (I was supervised at the age of 14/15, obviously!)

 

GOO doesn't want to run it underground, rather round the side of the existing shed/fence.

 

Not even 6 yet!