Shed

[antighsiothail]

Hi All
Looking for a bit of advice. Daughter has just moved into a bungalow, the place is split into 2 rings covering 4 rooms apiece. There is a shed she would like power to. The shed is just over 1.3 meters from the house, it's roof apex is 230 cm high and the house facia is 260 high. She won't be using any power tools in there, but would like a light and maybe the ability to use a small fan heater. So what I was intending to do is, break into the ring at a point nearest to the shed, put in 30amp junction box take the cable out from under the eaves across to the shed supported by a catenary wire, using a small pole to lift the cable at the shed end to the same height as the house. The shed by the way is about 6ftx8ft. The other point to make is that we are in Scotland not England. Forgot to say the cu has circuit breakers not fuses.
Are there any problems regulations wise to doing this?
The other question, is it ok to put the junction box under the loft insulation?
Many thanks for any help.

 

[PrenticeBoyofDerry]

It is okay to put a JB in the loft, providing it is accessible for inspection, test and maintenance.
But I would consider instead of a JB, having an DP isolation switch, so if the electrics in the shed ever became faulty, you can isolate from the house supply and then electrics in the house are not having power loss.

Any new sockets would require RCD protection.
And overhead cables are required to be at a height of no less than 3.5M (If I recall correctly).

 

[antighsiothail]

I understood the height to be 2.5 or 3.5 if vehicles may go under. The ring has rcd protection would this not be enough?

 

[Taylortwocities]

Basically, you are proposing an unprotected spur from a ring final.
You really should have a fused connection unit (FCU) at the house end to limit the current on the cable to the shed.

What size cable did you have in mind to go to the shed?
What would be at the shed end?

 

[ban-all-sheds]

But I would consider instead of a JB, having an DP isolation switch, so if the electrics in the shed ever became faulty, you can isolate from the house supply and then electrics in the house are not having power loss.

I'll see your DP switch, and raise you a DP switched FCU, as this looks like it's going to be a spur from a ring final.

 

[ban-all-sheds]

What size cable did you have in mind to go to the shed?

And what type?

 

[PrenticeBoyofDerry]

I'll see your DP switch, and raise you a DP switched FCU, as this looks like it's going to be a spur from a ring final.

Fold!

 

[PrenticeBoyofDerry]

I understood the height to be 2.5 or 3.5 if vehicles may go under. The ring has rcd protection would this not be enough?

If I recall vehicular access is a min of 5.2M

 

[antighsiothail]

So an FCU in the shed itself would be ok? In the house it would have to be in the loft, which isn't very practical. Sorry just seen you said at the house end.
As it's a very short run overall probably less than 3.5 metres, I was thinking of standard 2.5mm t+e, and maybe run it some plastic tubing. There would be no power tools or anything of that sort in there.

 

[antighsiothail]

Just seen a quote from the 17th edition "PVC insulated cable supported on catenary wire- height above pathway:3.5m min.
height above driveway: 5.8m min.
span: unlimited. "
So I think that answers that one, I'll need to lift it at the house end as well.

 

[riveralt]

As it's a very short run overall probably less than 3.5 metres, I was thinking of standard 2.5mm t+e, and maybe run it some plastic tubing. There would be no power tools or anything of that sort in there.

Don't bother with T&E outside - use rubber sheathed cable.
If you are only running a light then you only need 1mm 3 core protected by a FCU 3Amp Fuse.
However, it might be wise to run 2.5mm 3 core to the shed protected by a FCU 3Amp Fuse in case you want to put a socket in later - in which case a 13Amp fuse would be okay.
For the cable height - use common sense - I don't think anyone is coming around with a measuring stick - do you?

 

[JohnW2]

If you are only running a light then you only need 1mm 3 core protected by a FCU 3Amp Fuse. ... However, it might be wise to run 2.5mm 3 core to the shed protected by a FCU 3Amp Fuse in case you want to put a socket in later - in which case a 13Amp fuse would be okay.

It may be a bit more than a light ...

... She won't be using any power tools in there, but would like a light and maybe the ability to use a small fan heater.

It sounds that at least 1.5mm², probably 2.5mm², on a 13A fuse would be desirable. I must say, however, that my experience is that as soon as these very modest 'outhouse supplies' are installed, owners so often suddenly realise that they actually need more power in their outhouse than they had thought!

Kind Regards, John

 

[antighsiothail]

OK rubber sheathed 2.5mm cable it is, it will still have to come out of the loft. So where best to put the fcu?
There would have to be a socket in there but as I said my daughter isn't likely to be using power tools. I have today removed the feed to this shed, you'll love this. It went from the cu in the garage (which by the way is quite new and has rcd's on all the lines) out through the garage door frame clipped to the frame to the ground then buried in the gravel in front of the house about 1.5 inches deep, around the side of the house under grass also about 1.5 to 2 inches deep, but in the grass not even in a straight line to the shed it sort of curved round in a rainbow shape towards the shed. I'm talking about a run of about 30 metres of 2.5mm flat t+e, unprotected.

 

[riveralt]

OK rubber sheathed cable it is, it will still have to come out of the loft. So where best to put the fcu?
There would have to be a socket in there but as I said my daughter isn't likely to be using power tools.

The choice of the location of the FCU is up to you.
Things to consider:
You want it in a location that is accessible and isolation is easy - just in case you get a problem at the shed end.
So in the loft, high up on the wall near to ceiling or in the shed itself with an accessible Junction Box in the loft.

Is the shed wood and waterproof?
If not waterproof then you will need IP rated back box/FCU/ switch and socket in the shed - in fact I would put IP rated equipment in there anyway just for safety.
If metal then you need to consider the earthing arrangement.

 

[antighsiothail]

Yes the shed is wood and waterproof. An FCU in the loft would require to get ladders out, lift the hatch cover and get down to the far end of the loft on somewhat shaky planks laid over the joists. So would prefer to have it in the shed, as I said the run is only just over 3 metres so not a great length of cable.