Electric to Shed

[madmilner]

Hi all, Just posted this in the wrong place so copying here! Apologies!

i am not an electrician, and wondered if you could offer some advice.

I have seen posts on this topic but none seem to answer my queries in full, hence my post. Actually i found this forum through googling the topic in hand and thought, hey, giving i am going to be training as an electrician starting sept this may be a good place to hang out and ask questions etc.

We have just had an extension done on our house, single storey across the back, basically a bigger kitchen and diner. We are at a stage where the 1st fix has been done by the sparky and we are waiting for the plasterer. And when i say wait, i mean WAIT. its been ages now, but thats a different story.

So part of the project is to landscape the garden, which i am doing. Of which i am getting a bigger shed(currently have one) and want to run electricity to it. I mentioned this to the sparky doing our work but at the time he alluded to simply spurring off a socket, out the wall and it was as vague as that. To be fair i said it was an idea and not a requirement at the time. I just wondered how it would be done and where cables would run from. i.e would a cable to be run from the main fuse box. He didnt mention this at all.

My requirement is to have a double socket where we would run a tumble dryer off and a socket there should we need to plug in stuff like mowers etc, maybe a 240V drill? who knows. Oh and a light. thats it, no fancy garden lights, hot tubs, showers, freezers etc, just keeping it simple.

Now, i am in the middle of landscaping and need to crack on with the foundations for the patio etc. At the rate the plasterer is moving i could well have this all done before the sparky comes back for the 2nd fix etc.

I would like to dig the trench and run a cable etc so that i can get on with the patio. Then the sparky could connect up at a later date. I tried to call the sparky to run this by him but he may be away on holiday, either way he hasnt got back to me.

So to be clear, this cable run is going under a slate patio. From the back of the house(which is where the socket is that i am told we can spur off) to the shed its about 3 metres. Not going far. Not running much.

Are their regs to how deep this trench has to be? i read that its 600mm down(backfill), Electric Tile, 300mm of sand, Armoured cable, then more sand. Does this sound right?

Should i call building regs and they check my work or is taking photos so the spark can see what i have done going to be ok?

What cable am i looking at getting?

I assume i run some galvanised conduit up the vertical sections on each end of the run? then i would bundle the cable up and protect from the weather, while i wait for the spark to connect up each end and do it magic.

I appreciate i am new here and i am asking lots of questions, but any help would be appreciated.

Thanks

Mad M 

 

[steptoe]

put a duct in,

from the consumer unit [fusebox] to the shed, then your spark can do the calcs as to what size cable he needs, and if he can export the earth or not, and any main bonds that need to be installed, if required.

 

[Blue Duck]

...and if you decided you wanted an electric shower or a lathe up there in the future it will be A LOT easier to upgrade the cable!

 

[madmilner]

Thanks for the replies

ok sounds better to run a duct under the patio to let the spark have an access point. 

its the run to the consumer unit that could be the issue, he seemed to think we could exit through the back of the socket.

What about the trench, i assume there are regs or guidelines on this.

 

[steptoe]

run your duct to the CU

 

[Sharpend]

As advised by the right honourable spark for the mancunian area, a duct from shed to CU, or if access is readily available a cable of suitable requirement from the CU to a suitable position to exit property, followed by the duct to the shed. The cable requirements are to be determined by existing arrangements and the loading calcs,etc.

 

[madmilner]

Thanks again guys.

running a duct around the property is the most logical route, however its not going to be practical to dig up the entire route for the duct, i am only working in the back garden currently and just want to ensure a route/ duct is in place before i lay the patio. Its hard to explain but the patio is what will lie between the house and the shed so ducting under that is the priority.

I am now thinking, how much can this really happen given i dont have access to the CU. I was hoping to lay something under the patio that exits both ends (shed and House) so spark can feed something through at a later date. I just dont know the regs on the trench and duct to use.

If we said that from the shed to the back of the house its A-B and then from back of the house to the CU is B-C. I would ideally like to run a duct from A-B now, while leaving the B-C section until i lay the new path down the side of the house which is the run to the CU. 

A-B would be a straight 3 metre run but the B-C would then be a straight 9 metre run with an 90 degree turn then another 6 metres. Is this really practical for a spark to feed cable down?

Sorry for all the questions but given its a lot of work and lots to mess up i want to be sure on the approach.

Thanks

Mad M 

 

[apprentice87]

This is the sort of stuff you want.. If you had some of this, it would be dead simple to get just about any cable you wanted throught later. The twinwall stuff, [which is what you want] comes with a length of string already threaded through it. This is used to pull rope through, and then you can pull anything through it!! Just make sure that when you do the 90 degree bend that you make it a nice large radius bend, the bigger the radius the better.





 





I would get the 50/63 size. It is not the cheapest, but it is 2" diameter inside so easy to get cable through. The beauty of the twinwall stuff, is that it is corrugated on the outside for strength, but dead smooth on the inside, so no snags when you go to pull the cable through.





 





Oh yes, the trench, there are no fixed rules at all, just that it should be at such a depth that it it not "reasonably foreseeable" that it could be damaged at a later date [or words to that effect] This is usually taken to mean 450mm to the top of the duct, OR 600mm in areas where it is likely that people will be digging, say like flower beds!! Oh, and you can get a roll of yellow tape that has "electric cable" printed on it. Lay this in the trench about a foot above the cable if you want to be fussy!!





 





http://www.draindepot.co.uk/plastic-underground-ducting/electric-cable-ducting.html





 





john..

 

[Murdoch]

I would get said sparky back now to get his advice on the spot.

The internet is ok but there is no substitute for a site visit.

 

[madmilner]

This is the sort of stuff you want.. If you had some of this, it would be dead simple to get just about any cable you wanted throught later. The twinwall stuff, [which is what you want] comes with a length of string already threaded through it. This is used to pull rope through, and then you can pull anything through it!! Just make sure that when you do the 90 degree bend that you make it a nice large radius bend, the bigger the radius the better.

 

I would get the 50/63 size. It is not the cheapest, but it is 2" diameter inside so easy to get cable through. The beauty of the twinwall stuff, is that it is corrugated on the outside for strength, but dead smooth on the inside, so no snags when you go to pull the cable through.

 

Oh yes, the trench, there are no fixed rules at all, just that it should be at such a depth that it it not "reasonably foreseeable" that it could be damaged at a later date [or words to that effect] This is usually taken to mean 450mm to the top of the duct, OR 600mm in areas where it is likely that people will be digging, say like flower beds!! Oh, and you can get a roll of yellow tape that has "electric cable" printed on it. Lay this in the trench about a foot above the cable if you want to be fussy!!

 

http://www.draindepot.co.uk/plastic-underground-ducting/electric-cable-ducting.html

 

john..

Thanks John! Appreciate your help!

With regards to the radius bend, there seems to be products on that site for bends, well for every other size but the 50/63 size. Are these necessary? Or can you just turn the pipe, i would have thought it would have a natural ability to bed given it comes on a reel.

I guess the 90 degree applies to turning up the vertical path each end from the trench as much as turning corners within the trench.

This duct run will be completely under slate patio so no digging going on so sounds like 450 to the duct will be good enough, ill stick the tape down in case we ever move and the new guys don't like the path/patio. May as well give them notice of electric underground.

Thanks!

Mad M

 

[madmilner]

I would get said sparky back now to get his advice on the spot.

The internet is ok but there is no substitute for a site visit.

I have tried to reach the sparky but no response. Got a feeling he is on holiday and i really need to crack on with the patio/ groundwork. 

Unless someone disagrees, it seems a safe bet not to worry about the cable and earth etc and as advised above put a duct run in from the shed to the Consumer Unit. Although i cant do the entire duct run, with the knowledge of what duct to buy and use and the depth to dig, i can lay this as i work my way around the property over the coming months while i gradually break up the existing concrete path, dig the trench and un real the duct. I am in no rush for the electric to the shed, i just want to ensure the foundations are right given i am there now with a spade. not in a years time when i have spent £££s on a new patio and path. 

Sound like the right way to go or is there still reason to wait for the spark?

mad M

 

[apprentice87]

I would just get on and lay the duct. As you say, you do not need bends, you just bend the duct. Do not try tight bends though, the bigger thr radius the better, as i said, about 18" radius as a minimum, and make sure the string does not disappear in the duct!! Pull a bit of 6mm rope through, adn when you pull your cable pull another rope with it and leave it in the duct incase you want to pull anything else through in future. I cannot see any problems pulling the cable through, someone pulling the rope and someone else pushing the cable [like you would a drain rod] and it should fly through!!

You can get end caps to go on the cable, or tape them up so that the thing does not fill up with water or have things living in it!!

john..

 

[madmilner]

thanks John, duct turned up today with rope. Spent last 3 days filling a skip up with the old paths.. amasing what you find in the ground when digging up the original path from the 70's!

Once i cleared the route ill dig a 400mm trench.

M