Easiest way...

SSE · Sep 7, 2011

Asked to have a look at a job at an old old house (never good). Anyway all the guy wants is power in his shed in the back garden for three double sockets and one strip light (about 3/4 metres from the house). Only problem being theres no way of getting to the consumer unit as it's at the far away end of the house and all floors are laminate flooring so can't be lifted and theres no underfloor access. The closest power to the shed is part of the ring that's in the extension and outwith this theres no other access to the house as the walls are literally a metre thick or more thick and even getting through the walls wouldn't help as laminate flooring everywhere.The extension was wired before the laminate flooring was put down, all from below. Just wondering what the best way to go about this would be. I always have just run a 6mm supply to sheds, never tapped into circuits and infact don't even know if your allowed to, I always thought a shed would have to be on it's on circuits to comply with regulations.

SSE · Sep 8, 2011

GLENNSPARK said:
Could you not use the 6mm as a draw wire?...use that to pull a 10mm in? As tel asked earlier in this thread are there any extranious conductive parts within that shed?....an outside tap maybe?.........

No it's not a straight forward run to be able to use as a draw wire, it just wouldn't pull. I just put it down on my test sheet that it didn't comply and correct me if I'm wrong but I'm pretty sure that's my end covered? As soon as the floor is lifted it'll be upgraded to a 10mm.

Sorry I forgot to reply regarding the extranious conductive parts. No there are none that I can think of off the top of my head. The outside tap is on the house wall.

GLENNSPARK · Sep 8, 2011

Well thats better for you as you would have had to extend the equepotential zone from the house to the shed in 10mm as its a TN-C-S earthing arrangement.
As far as the 6mm bonding is concerned i was under the impression that it had to comply with the current edition of BS 7671 before undertaking any more work. But others may post thats wrong in which case i will happily stand corrected.

SSE · Sep 9, 2011

GLENNSPARK said:
Well thats better for you as you would have had to extend the equepotential zone from the house to the shed in 10mm as its a TN-C-S earthing arrangement.
As far as the 6mm bonding is concerned i was under the impression that it had to comply with the current edition of BS 7671 before undertaking any more work. But others may post thats wrong in which case i will happily stand corrected.

Mmm, I've never heard this but certainly ain't doubtin' it's true. Could well do with finding out though as I'm meant to be doing it tomorrow!!

GLENNSPARK · Sep 9, 2011

check out tel`s post (13) mate.....

SSE · Sep 9, 2011

GLENNSPARK said:
check out tel`s post (13) mate.....

Ah never noticed that post. Looks like I'll maybe have to put this one hold then until he lifts the flooring so as that I can upgrade the earth to 10mm.

Also, to what extent does this go? ie are you saying if theres still a 6mm then no electrical work at all can take place in the house?

Octopus · Sep 9, 2011

gallagher said:
Ah never noticed that post. Looks like I'll maybe have to put this one hold then until he lifts the flooring so as that I can upgrade the earth to 10mm.

Also, to what extent does this go? ie are you saying if theres still a 6mm then no electrical work at all can take place in the house?

BRB 131.8 is worth a read in such situations, then its up to you to determine what's necessary.

10mm is mandatory for rewires/new installs

telectrix · Sep 9, 2011

apply the adiabatic to the main earthing conductor. if the answer is 12mm or less, then the 6mm can stay as long as it's intact and shows no sign of deterioration, until it can be replaced. ( note in comments on cert.)

ezzzekiel · Sep 9, 2011

Agree if readings are ok and no signs of damage then no reason why it cant be left just note it on cert

SSE · Sep 9, 2011

Went to job today and explained everything to the guy and after a while he decided to lift the flooring that I needed as it's gonna be coming up soon enough anyway. When he lifted it though he had to cut a track in the flooring under neath and he ended up sawing a pipe in half with the electric saw!! Water evrywhere!! Managed to get a clear enough run and just put a 6mm supply in for the shed and upgraded the earth to 10mm. Thanks for everybodies input though, picked up a couple of things I never knew anyway! Still learning every day! ha

Knobhead · Sep 10, 2011

Archy Styrigg said:
Could you run SWA up the outside of the front of the house, into the roof space then down the back wall into the garden?

Another way around this.

If it’s an old house in a terrace I would be surprised if it doesn’t have a cellar. Get yer sen down't cole ole lad!

La Poste · Sep 10, 2011

Just reading this thread and thinking if your were to take a spur off the ring main why would the spur have to be 2.5mm?

I mean the ring is fused at 32A so why not use a bigger cable say 4mm.

I don't have my regulations handy but is it against the regs to spur off a ring with a larger cable and use the 32A fuse at the DB as the circuit protection?
The ring is effectively a 5mm cable anyway (2 times 2.5mm)

It would be like an unfused spur but capable of carrying the full ring current of 32Amps.
This would then supply the shed with potentially more options.

The spur doesn't have to be a socket, it could just be an adaptable box.

I mean it's OK to extend the ring into the shed so why not spur off the ring with a larger single cable to save running two cables?

You are allowed to have a lasso configuration when a 4mm single cable becomes a 2.5mm ring so why not this?

This is more of a technical interest question than a practical one.

If the answer is no I just wonder what the logic behind it is.

P.S. I'm still a student.

Thanks.