RCD on a Ring Circuit extension

[Tordelbach]

Hi all,

Fascinating forum, have learnt much by lurking here, but this is my first post. I have tried the 'search' facility, but can't find the specific problem I'm looking for, so here's my situation:

I want to supply power to a detached garage 5m from my house, to run basic lights, two double sockets (light power tools, convection heater, maybe a laptop) and a transformer for low-voltage outside lighting and small pond pump.
I aalso want to take a weatherproof socket off the same cable (lawnmower, strimmer, radio etc.) .
I'm in a brand-new house with plenty of outstanding jobs to do, and so am deeply reluctant to run new cable to the CU at this stage (it's on the opposite side of the house) with the resultant additional decorating chores.
Therefore, my plan was to extend the ring circuit from the rear of the house, mainly because I had understood from various manuals that taking more than one socket off a single spur was a Bad idea (my reading here has suggested I may have swapped one on-no for another).
While doing initial gardening several months back, I took the opportunity to dig a trench and to lay thick plastic conduit at 500mm depth, and lay two runs of 2.5mm 2-core-and-earth cable inside it, before getting on with planting above it. Calculations of voltage drop for this setup do seem to be just about okay (under 9V anyway), and while I do understand that this may not be by any means the best approach, I'm reluctant to change direction at this point (although open to your declarations of horror).

My main question is this:

I want to protect the whole "outdoor" run with an RCD. Without going back to the CU, what is the best way of doing this? Using all RCD-protected sockets looks to be the simplest of protecting the user at the appliance end, but how does that help with response delays on the actual buried cable?

Would it just be wiser to scrap my work to date, and just run a 6mm2 spur from the back of an existing socket? Or must I bite the bullet and start running cable through my nice new plasterwork

Thanks in advance, folks.

 

[breezer]

there are 2 ways to do a job, the right and the wrong way. you decide.

then read the posts your search brings up

 

[andy]

6mm spur from a socket... remember. your limited to 13A. and your idea of T&E in pipe isnt acceptable. do it properly and put the garage on its own radial direct from the CU using SWA for the outside part

and if you search for garage supply etc, then youll get loads of results for what you should do

 

[Steve]

Rather than going through the house with the new circuit cable, cant you go around the house? (clipped to the wall) Since usually the consumer unit isn't far from an outside wall.