Wiring a Shed

Redjeep!

Hi Folks,

I'm having a large garden shed built, and I want to run wiring to it from the house.

Does anybody know the regulations for wire gauge etc ?

My plan is to run a cable from the main distribution box in the house underground to the shed and then fit a small RCB distribution box in the shed. I want around a dozen sockets and probably 2 or 3 low current lights. I'll want the sockets for power tools and the number is more for convenience than anything and I can't see me ever have all 12 used at the same time.

What I want to know is the correct wire gauge for the wire from the house, the ring main and the lighting circuit.

BTW My intention (before anybody says anything) is that I'll run all the wiring and then get a sparky to check it all and do the final connections.

The shed is about 30yds from the main house distribution box.

Thanks.

ircoha

Hopefully some of the sparks will come on later after the pub.

http://www.tlc-direct.co.uk/Technical/Lighting/VoltageDrop.html

There are voltage drop calculators available on line. which suggest that 2.5sq would get u out, assuming you are only using normal power tools. I would use 4sq just for that extra bit of comfort. there is not much difference in the price
http://www.tlc-direct.co.uk/Main_Index/Cable_Index/Armoured_SWA/index.html uk prices!!

When I did mine I ran a separate light cable so as if I tripped a breaker at night the light stayed on. Prolly 1.5sq

Also consider running an alarm cable and a cold water feed while u are at it.

Finally there are mor sensitive ELCB's for use outdoors. I would use them for the garage.

CJhaughey

Funnily enough I am doing the exact same thing right this minute.
I have 30 amp SWA armoured cable running direct from the CU in the house to the shed.
My plan is to install a 2 way CU in the shed and run a 63 amp switch and a 6amp MCD lighting circuit and a 32 amp MCD for sockets, these will still trip back in the house CU if necessary.
SWA cable is metal armoured and is essential for safety if you want to avoid electrocuting someone if their shovel contacts an underground cable.
I have also run 3/4 water pipe in for a WHB and tap.
this is useful for a variety of things in a workshop.
I am also looking at plans for making a small woodburning stove for the winter months, a few people have some good ones made from old calor gas bottles.

Redjeep!

Wow, that was fast.

Thanks for the replies. If I'm running the cables through conduit then does it need to be armoured ? I'd assume not. I've got two options, the first is to dig a trench and drop a length of ESB conduit in (one end is already in place). The other is to try and persuade a second cable down the conduit that supplies my main house supply and runs about 2 feet from the shed.

I think that the idea of the alarm cable and possibly a seperate lighting cable are great ideas.

What type of shed are you doing CJ ? I was just thinking of a large wooden shed (typical garden shed but 20ft x 12ft), it sounds like you may be doing a block version. I was put of by the thought of digging the foundations and the need for planning permission.

I've seen the heater plans I thought that they looked great, but was a bit wary of cutting up a calor gas cylinder (boom) so was thinking more along the lines of a small 'ready made' woodburner. I've seen a few over the years that were designed for caravans or boats and would have been perfect. Still a bit nervious about a wood burner in a wooden shed though....but reckon it would be OK sat on blocks and the chimney is well insulated from the walls. afterall they used to have them in wooden boats didn't they.

CJhaughey

You don't need to use anything with SWA as it is already armoured.
My shed is 18' by 15' and is of all wooden construction bar the foundation which is insulated concrete.
I am going to give the Calor Gas woodburner a go, I have a couple of old bottles and an arc welder and hey it will be my first shed project!
Of course safety will be my primary concern.
There is a few pics of pretty professional looking ones at albioncanvas.co.uk but they are essentially just a gas bottle stuck to a car rim, hardly rocket science with expensive materials

Redjeep!

CJ - check out readersheds.co.uk as well. They've done the calor gas thing as well.

BTW my thoughts with the cable were kind of the opposite to what you mentioned in that I'm going to use a conduit and then put some 'regular' twin and earth 30A cable through it. I've already bought some conduit and sunk one end of it, but before I dig the trench though I'm going to try and feed the cable thro' the conduit that supplies the feed into the house as it's about 2 feet from the shed. I don't think I'll be able to get the wire through the conduit as there's already a cable going thro' it and I feel they'll get stuck. If it works though it'll save me a lot of digging.

ircoha

In relation to using non-armoured cable in a conduit, there is an out door non armoured cable pronounced "ruzie" which is sometimes put in a conduit. However if water gets into the conduit the cable lasts about 5 years.

I cannot comment on the the normal pvc T+E in a water filled conduit.
I would go armoured, conduit or not

CJhaughey

Armoured is much safer, if someone is digging with a shovel and goes through the conduit/cable they won't be happy!
It would be very hard to do that with armour cable.
Electricity takes no prisoners, better safe than sorry.
AFAIK it is a requirement that external cables are armoured.

Redjeep!

Thanks - sounds like the way to go is to use the armoured. Not a problem I'll get some when I need it.

What did you build your shed out of CJ ? I'm split between ordering some kind of garden shed/ log cabin and building one out of treated 4x2's.

ircoha

CJhaughey wrote:

Funnily enough I am doing the exact same thing right this minute.
I have 30 amp SWA armoured cable running direct from the CU in the house to the shed.
My plan is to install a 2 way CU in the shed and run a 63 amp switch and a 6amp MCD lighting circuit and a 32 amp MCD for sockets, these will still trip back in the house CU if necessary.
SWA cable is metal armoured and is essential for safety if you want to avoid electrocuting someone if their shovel contacts an underground cable.
I have also run 3/4 water pipe in for a WHB and tap.
this is useful for a variety of things in a workshop.
I am also looking at plans for making a small woodburning stove for the winter months, a few people have some good ones made from old calor gas bottles.

I am not a sparks but it seems to me that if u have a 63 amp fuse or switch in the shed which is the same as the one on the house board, u could, in theory blow the house one before the shed one due to the voltage drop.

Power is equal to Voltage * Current so if for the same power and reduced voltage u need more current

I always use a lower amp fuse in the shed, it sort of makes sense intuitively, but could be complete bollox!!:)

The other thing u might consider doing with a metal shed is to put in an earth rod c/w 10sq earth cable connected to the shed itself- just in case:)

Lastly, if u buy or make a wooden shed, it can always be moved.

I screwed/bolted the panels together
I moved my kellys shed 3 times in 12 years.

un-insulated metal sheds will be v cold

CJhaughey

My shed from the outside in is as follows,
Shiplap pine on 50mm pine battens, Blizzard Pro T-underlay (polypropylene), 10mm OSB board and 100x50mm studs at 400mm centres.
roof is 20º pitch with 10 mm OSB on 100x 50mm reinforcements on top of 3 trusses + gable trusses.
Windows are Elitfonster triple glazed 1 fixed in western gable and one opening on S side.
Doors are 1 x Swedoor 1mx2m on S side and an Edsbyporten double garage door to the E side.
Maybe a bit of overkill on the windows and doors but I plan to insulate the shed well with Rockwool and Polystyrene for warmth in the winter.

ircoha

CJhaughey wrote:

My shed from the outside in is as follows,
Shiplap pine on 50mm pine battens, Blizzard Pro T-underlay (polypropylene), 10mm OSB board and 100x50mm studs at 400mm centres.
roof is 20º pitch with 10 mm OSB on 100x 50mm reinforcements on top of 3 trusses + gable trusses.
Windows are Elitfonster triple glazed 1 fixed in western gable and one opening on S side.
Doors are 1 x Swedoor 1mx2m on S side and an Edsbyporten double garage door to the E side.
Maybe a bit of overkill on the windows and doors but I plan to insulate the shed well with Rockwool and Polystyrene for warmth in the winter.

TV and broadband to follow I presume.

In passing, while it might be a bit more expensive might be easier to use something like this
http://www.roof-solutions.co.uk/insulationguide_158895.html

try u-value insulation on 01 836 5299 it goes on ith a heavy duty stapler

http://idimn.com/pages/staples_staplers.html

CJhaughey

LOL I haven't even got TV or Broadband in the House!
What I was planning on doing for the roof of the shed was a simplified version of the way my house roof is insulated.
I tack on battens to the inside of the OSB sarking, these can be only 20mm thick, then I stick hardboard on top of these, this creates an air gap to allow the roof to dry, I can then use whatever insulation method I choose to insulate the roof without fear of causing dampness.
That foil looks interesting but holy jebus 125 stg per roll!!
Probably cost more than the shed to insulate it!

ircoha

the hardboard may sag if the span is too much.

yes it seems a bit expensive but it makes the place very bright, I have it in the attic space and it is A1.
The theory is it is = to 10 inches of rockwool, u could but it on in your office suit.

Copper

Because you want 12 sockets (more than is in my house!) I would run 4 square SWA fused at 32A in the house. Otherwise I would run 2.5 square.

SWA already has adequate mechanical protection and can be buried directly into the ground at a depth of greater than 450mm (in a garden).

Cables ran in ducting generally don't require additional mechanical protection. If I was running cable through the ducting I'd use 4 square NYM. Whichever method you use you should also bury warning tape (at a depth of around 200mm) to indicate the location of the cable/ducting, could save you a lot of hassle if you ever get your garden dug up.

If your house mains is fused at 63A then every fuse downstream of it should have a lower rated current.

FX Sheister

CJhaughey wrote:

I have 30 amp SWA armoured cable running direct from the CU in the house to the shed.
My plan is to install a 2 way CU in the shed and run a 63 amp switch and a 6amp MCD lighting circuit and a 32 amp MCD for sockets, these will still trip back in the house CU if necessary.
SWA cable is metal armoured and is essential for safety if you want to avoid electrocuting someone if their shovel contacts an underground cable.

It sounds like you don't really know what you're doing. Are you getting an electician to look at it before you start using it? If your supply cable can only carry 30A then why is your main switch 63A and your Socket MCB 32A? I presume your sockets will be wired on a ring main in 2.5mm if you plan to use a 32A breaker. They should also be on an RCD. The armour of your SWA cable must also be earthed properly. What is your SWA cable connected to back at your main board in the house? You say it runs direct but I presume you have it running from an MCB and not direct from the bus bar or main switch fuse.

Redjeep! :
You can have ten double sockets on a radial circuit, maybe that would be enough for you. If you want more then you can use a ring main allowing you to put on as many sockets as you want within 100 sq. metres.
You shouldn't run regular 2.5 cable in the duct, you should use NYMJ. "Ruzie" that was mentioned is not used anymore but some people incorrectly refer to nymj as "ruzie". You don't have to run armoured cable, it is not a requirement.

CJhaughey

You are dead right sheister no point in fúcking about with electrics, My sparks is coming over this week to finish the house and I will get him to install the CU in the shed, I was only going on the specs that were given for the small CU's most of them have a 63 amp breaker and a 32amp MCD supplied, makes sense that the cable should be heavier than the trip.
I'll let you know what I end up doing.

lloydyboy

CJhaughey wrote: »

You are dead right sheister no point in fúcking about with electrics, My sparks is coming over this week to finish the house and I will get him to install the CU in the shed, I was only going on the specs that were given for the small CU's most of them have a 63 amp breaker and a 32amp MCD supplied, makes sense that the cable should be heavier than the trip.
I'll let you know what I end up doing.

I had my shed wired at the weekend...6sq SWA from 32A at the house board into a 4way unit at the shed. this has a 63A 30ma RCD switch with 6amp for light and 20 for sockets. Spark wired it so that if sockets trip the light stays on. he said important factor was the 30mA rating of the RCD...63Amp only means it can take up to 63amp. Obiously if you go for a fused main switch then you have to install an RCBO for the sockets which are expensive.

Anyone disagree ?

M cebee

if it's a 4-way board (rcd and 2mcbs) then the rcd will have to break the lights if it's being used as the 'main isolator'

rules require a 'main switch' with rcd preferably not breaking lights ,as you say

so main switch,rcbo and lighting mcb would be better for a 4-module

Quicktwo

I'll be wiring my shed soon, but I'll be starting to buy the stuff soon. I plan on welding there, mig and arc. What size SWA cable do I need?
I want 10 sockets, 4 fluorescent lights, 3 smaller lights, the welders, and it's about 35m from the house.
Any help appreciated.

Sir Arthur Daley

Quicktwo wrote: »

I'll be wiring my shed soon, but I'll be starting to buy the stuff soon. I plan on welding there, mig and arc. What size SWA cable do I need?
I want 10 sockets, 4 fluorescent lights, 3 smaller lights, the welders, and it's about 35m from the house.
Any help appreciated.

Get a Registered Electrician.

Quicktwo

I will, but I'm buying the stuff over the next few weeks.

Sir Arthur Daley

Quicktwo wrote: »

I will, but I'm buying the stuff over the next few weeks.

Your electrician will make up the list for you.

ltz400

I have bought a metal shed but have not got it yet and no concrete base in yet my question are

(1) going to run 10sq swa from main fuse board in house to shed fuse board or is this cable over kill

(2)50a main breaker in shed so what size should i run on the house board

(3) i have 1 shed with fuse board in it runnin washing machine tumble dryer
fuse board layout there is main fuse 50a, rcd 40a, 2no 20amp b type, sockets, 1no 10amp lights
now the main cable supplyin this board is 2.5sq swa but that is runnin along side the new shed so was thinkin of romovin from the house fuse board and connect to the metal shed fuse board and put that on a 50a rcbo
what do ye think of that idea. the cable run from house to metal shed is 23m

power needed in shed well what i was thinkin

2no 10amp for lights mcb b type
1no rcd 40amp
2no 20amp b type for sockets
1no 20amp d type for welder

also down the line i will be putting a change over switch on the house board to run a geni out in the shed so now the time to put the cable in would 10sq swa be over kill

Sir Arthur Daley

ltz400 wrote: »

I have bought a metal shed but have not got it yet and no concrete base in yet my question are

Are you an electrician?

ltz400

WikiHow wrote: »

Are you an electrician?

No i am not a sparks but my couisin is and he is commin over for hols at easter said he would do t job but would like to get everything before he gets here plus need to put cables in so i can put concrete base down for shed so thats why the question i will not do any final instal

slimjimmc

ltz400 wrote: »

No i am not a sparks but my couisin is and he is commin over for hols at easter said he would do t job but would like to get everything before he gets here plus need to put cables in so i can put concrete base down for shed so thats why the question i will not do any final instal

Is he a Registered Electrical Contractor (REC)?

If he is then perhaps he should be the one to specify the materials since he's the guy who will be doing the job.

If he's not then I doubt he is legally allowed to take on the job as what you're proposing is not minor works as it involves a new circuit.

http://www.safeelectric.ie/

From the 1st of October 2013 only a Registered Electrical Contractor (REC) can carry out most electrical work in your home *
Registration under Safe Electric means the contractor is registered and insured
The contractor must issue you with a certificate to show the work is of an approved standard
To find a Registered Electrical Contractor click on either of the two logos below.

* Excluding Minor Works, click here for more info

http://www.irishbuildingmagazine.ie/2013/08/13/commission-for-energy-regulation-enacts-new-safety-legislation-for-domestic-electrical-contractors/

ltz400

We'll he is rec legally able to do the as I said I will not be doing final instal just want to know about the cables as concrete base is going in next weeken

But if u want to be a**hole about it then get off this site as I thought this site was for advise and not for givin out

slimjimmc

ltz400 wrote: »

We'll he is rec legally able to do the as I said I will not be doing final instal just want to know about the cables as concrete base is going in next weeken

But if u want to be a**hole about it then get off this site as I thought this site was for advise and not for givin out

Giving out ? LOL.

This is your situation: you've a looming deadline, you're unsure of your specs, no one here has A-OKed it yet, so what is so unreasonable about asking your cousin's advice? (Or is is that your cousin gave you those specs and you're unsure of his advice?)

BTW Have you considered burying a plastic pipe or laying trunking when pouring the slab and pulling the cable through later? That would take some of the pressure off.