Taking power to a Shed / Garage.

[sweeneyuk]

After some advice from the experienced sparks out there.

I have built a concrete base at the end of my garden ready for a 15' x 10' summerhouse to go on.

I need to take power to it for s/o & lighting.

The shed is approx 12m from nearest part of house which is a kitchen extension.

Need to take pwr from main CU under stairs in the house, best route i can see is to take it up to my loft then out through eaves, down exterior wall around eaves on extension & along concrete fence posts.
My extension roof cavity doesnt line up with floor cavity of house so running under floorboards into extension roof cavity is out.

Questions.

1. should i run 10mm up to the loft & into an adaptable box by the eaves, run 10mm swa from the box out through eaves along walls & through black pvc conduit attached to fence posts?
then Run it straight in to a metal clad CU inside shed.

2. Could i just run 10mm t&e all the way using blk pvc conduit for the exterior run?

3. Should i use a 40A rcbo at main CU in house with a 32amcb ring in the shed or just a 20a mcb radial for s/o's? will use a 6Amcb cct for lighting.

Want to avoid burying anything as i have a patio in the way.
Looking for the easiest most cost effective way to take pwr to shed.

Have a load of 10mm left over which i'm hoping to use.

Did consider a fused spur from a s/o on kitchen ring in the extension but as this will limit me to 13a in total have now ruled it out.

Is there an easier way?

any help appreciated.

 

[DurhamSparky]

out of the options you have given i would take the 10mm up to the eaves where you can swap cable to swa and take outside along fence and into the shed terminating at the CU.

what earthing method are you using for the shed??

 

[londonlec]

Run SWA all the way.

PVC externally is very poor, just wait for the sagging.

 

[DurhamSparky]

mind you what are you intending running from your sockets as 13a may be enough!??

 

[Guest123]

.what earthing method are you using for the shed??

******!!!!!!

 

[DurhamSparky]

******!!!!!!

now come on lenny!! we all know this is a good subject!!

 

[PC Electrics]

No harm in using the 10mm if you already have it and it would otherwise go to waste. Do you have all the cable for the distribution circuit?

As for what protection: first thing is to determine your design current. Have you done this?

Obviously it depends upon the expected loading, but I would have thought a 20A radial for sockets would be sufficient for this summerhouse. If your loading includes any heating this can be on its own radial. You could then use a 32 or 40A at the house end depending on your design current.

 

[PC Electrics]

Using SWA all the way will be a lot easier than trying to put 10mm t&e into conduit.

 

[Octopus]

Don't forget its notifiable to LABC

tin hat on!

 

[Deleted member 26818]

10mm² T&E should be good for 50A, but even if you do go for 40A there's no reason why you can't do 32A for power and 6A for lights in the shed.

 

[sweeneyuk]

Missus wants a bar inside, i will def be having a little workshop with max power item prob a 2kw chop saw. so other than lights there will poss be a tv & heater in winter. nothing decided for sure but want to have enough spare capacity to future proof.

Will i need to add an earth rod?

Shed CU will be rcd protected, swa earthed at 1 end if i use 3 core swa & use 3rd conductor for earth.
Main CU will have a 40a rcbo on my split load board.

Been a while since i completed 2360 have worked for thames water since so my knowledge 100% without going back to my notes & books but how do i determine if an earth rod will be required ?
Will the rod be in addition to existing cpc or do i not run earth continuity from main house if using a rod?

Just for info sake, if i were to come off the kitchen ring with a fused spur, would i still run it into a CU in the shed? Presumeably i'd have to down rate the mcb's for radial & lights on the shed CU not to exceed the 13a FCU in the kitchen right?

Does the SWA have to be buried or in conduit? pvc conduit may sag on the runns between the fence posts as mentioned, running the swa along the fence posts will also sag.

really dont want to have to lift the patio slabs etc as i will have to go under a wall & all sorts to bury, what other options are there?

appreciate all the help.

 

[Deleted member 26818]

It used to be that you contacted the DNO before exporting the earth on TN-C-S.
It appears nowadays that you'll be lucky to even find someone at the DNO who knows what colour their hair is without using a mirror.
If your system is TN-C-S, and you have extraneous-conductive-parts in the shed/garage, you will either have to provide an adequately sized bonding conductor (10mm² minimum), or TT the shed/garage. Whilst the armour of the SWA will most likely be sufficient as a CPC, it will not be sufficient to act as a bonding conductor. If you do TT the shed/garage, then you will have to keep the main installation earthing separate from the she/garage sytem.

I wouldn't protect the SWA with an RCBO, as this will not minimise inconvenience in the event of a fault, and as you intend installing an RCD at the shed/garage, this will mean there are two RCDs in series.

If you were to spur off the kitchen ring, you would not neccessarily have to install a CU in the shed/garage, you could spur off again for the lights in the shed/garage. However by doing such, you would be limited as to the load you could have in the shed/garage.
You would not have to bury or use conduit for the SWA, as the armour provides mechanical protection. If you were to use T&E, then depending on the route, mechanical protection may well be advisable.

To my mind, the best way would be to use SWA from a non-RCD protected way in the house CU to the shed/garage. Install a CU at the shed/garage with an RCBO for the socket-outlets.
As you have some T&E knocking around, then it might be cheaper to use that, and run it in conduit, the only thing being that you will have to RCD protect the T&E if it is concealled in any walls. If you do then you would not require RCD protection at the shed/garage.

 

[telectrix]

as spin says, but would not spur off kitchen as you would be limited to 13A total. your chop saw and heater wouldpossibly wipe the 13A fuse out. SWA IMO, is the best way to go. if you space the cleats closely, you won't get sagging.

 

[Wiredspark]

Also to avoid sagging between the fence posts, nail on a new horizontal batton or two to allow you to fix the SWA to it. Defo go SWA, best job.

 

[londonlec]

Also to avoid sagging between the fence posts, nail on a new horizontal batton or two to allow you to fix the SWA to it. Defo go SWA, best job.

I agree, gravel board horizontally?

 

[sweeneyuk]

Thanks for all the good advice.

Will def add some kind of batton along fence posts to attach the swa cleats to.

Summerhouse is all wood construction inc window frames so assume i'm good to carry through the cpc?

Should i use 3 core swa & use 1 conductor as earth, earthing the armour at 1 end only?

Will come off the non rcd side on home fuse board using a 40a mcb as suggested then rcbo the ccts inside the shed CU.

As i have 10mm T&E left over will prob run that up to eaves then through adaptable box into swa. will take swa all the way into metal clad CU in shed.

Now making relatively tight bends using 10mm swa, any advice on best methods?

Also should i use 3 core

 

[Deleted member 26818]

I wouldn't bother with 3core. Just use the armour as the CPC.

 

[mike2790]

the way i would do it is to take some 10mm tails into an enclosure with a 100mA RCD and a 40A breaker, come out of the breaker with the 10mm twin you have lying around into an adaptable box, i would definately use 10mm SWA for outside earthed at both ends (personally i like to use 3 core and use the remaining core for earth but the armoring would be okay), into a metal clad CU in the shed, 30mA rcd, 32A ring or 20A radial (wired in 2.5mm) for sockets and a 6A circuit for the lighting. job done.

 

[Wiredspark]

Earthing the armour at one end only? er why? For the little extra cost of a 3 core, yes I'd use 3 core. A little extra protection is NEVER a bad thing.

edit: If you are only gonna earth at one end, just how are you gonna terminate at the other???

 

[telectrix]

Earthing the armour at one end only? er why? For the little extra cost of a 3 core, yes I'd use 3 core. A little extra protection is NEVER a bad thing.

edit: If you are only gonna earth at one end, just how are you gonna terminate at the other???

plastic SWA gland?

 

[Wiredspark]

never thought of that

 

[sweeneyuk]

the way i would do it is to take some 10mm tails into an enclosure with a 100mA RCD and a 40A breaker, come out of the breaker with the 10mm twin you have lying around into an adaptable box, i would definately use 10mm SWA for outside earthed at both ends (personally i like to use 3 core and use the remaining core for earth but the armoring would be okay), into a metal clad CU in the shed, 30mA rcd, 32A ring or 20A radial (wired in 2.5mm) for sockets and a 6A circuit for the lighting. job done.

I assume you would use a 100a tails connector block to run 10mm tails into seperate 100ma rcd enclosure?

Only reason i suggested earthing at 1 end is i've read that using the core & armour will give a parallel earth path, not sure on how adversely this will affect results though?

 

[Wiredspark]

I assume you would use a 100a tails connector block to run 10mm tails into seperate 100ma rcd enclosure?

Only reason i suggested earthing at 1 end is i've read that using the core & armour will give a parallel earth path, not sure on how adversely this will affect results though?

why not use this

 

[Deleted member 26818]

There's nothing wrong with having parallel earth paths in this particular case.
In some instances, with sensitive equipment, such as guitar amplifiers and perhaps some inverters, there can be problems with earth noise.

 

[sweeneyuk]

Does the space underneath the kitchen units behind the kickpanel constitute a viable enclosure to run cable?

Only ask as it would be the most direct route to get cable to outside wall of extension & save a lot of cable.

I doubt i will be able to reach far enough to clip it direct the the rear wall under there but maybe it could be run through some flexible conduit?