Spur Length ??

[skybluescooby]

Following advice sought on installing a new plug to our bedroom without having to rip up floors or dig into walls i have found a solution that will involve running a spur from the garage ring main, up and through the wall into the airing cupboard and up to the loft, across the loft beams and drop into the bedroom/en-suite stud wall and come out 6" from ceiling height into bedroom wall.

With this in mind is there any regulation on the maximum length a spur can be.
It will be coming from a ring main powering 4 double sockets of which an electric garage door and two external pir spots are permanently connected.
Regards

 

[Paul Barker]

What a professional would do is get it from somewhere else, but if this was the only option he would calculate the voltage drop which must be less than 4% from the distribution board to the final socket. He would also have to be sure that R1 and R2 were sufficiently small.

You do need professional help in designing and testing your proposal..

But if you insist on carrying on you might want to consider using 4mm tne and might even need a 4mm protective conductor.

 

[philrosenberg]

I agree with Paul I would only do this if it was a final resort. Just thinking of the future owner, if they wanted to replace the faceplate or something it could easily happen that they might assume the socket was on the ring and turn off the wrong circuit. This happened to me with a socket in our living room. It had two cables coming to it in 1.5 T+E, I just assumed it was on the ring, turned out it was on the lighting circuit I had a lucky escape there.

Also bear in mind hidden cable can only be routed in safe zones, ie directly above, below or to the side of sockets or in corners or by the ceiling.

 

[skybluescooby]

Hmmmmmm this is becoming more difficult than i thought, Before i call in the pro's in your experience guys is there anything in the average 10 yr old loft that i can tap into.
Other question is, the wall with the sockets is plasterboard dot n dab, is it easy to just drop a cable from the loft down the void and hook up to the back of the socket ? being very optimistic here i think.

 

[philrosenberg]

I guess it will vary house to house I'm afraid.
All my wiring is in the loft, but I live in a bungalow with concrete floors so it has to. I guess in a modern two story most of it will be between downstairs ceiling and upstairs floor. You'll just have to get up there and check.

Could you remove another socket and it's box in the same room and try feeding cable down to that hole from the loft? Then you could take it accross the ceiling and down the wall where you need. Just a thought, I've never tried it so don't know how easy it is.
I don't think there are any implications for supporting the cable over those heights but I'm not sure if there are issues with the cable winding about behind the plasterboard out of safe zones

 

[Paul Barker]

Dot and dab is bad news. Probably least disruption to take spur off socket in same room, straight down along under floor back up.

If it's 10 yur hs floor will be wheetabix ringnailed. I love joiners. Have fun.

 

[securespark]

It's not as technical as you think. Get hold of an EFLI tester. Attach a length of cable to the socket you intend to run off the length it will be if installed in the route you propose. IE if the cable run from garage to bedroom is 18.5m, then use a 18.5m length of cable.
Put a socket on the end of this cable, then do an earth loop on it. Assuming the garage ring final is on a 32A B type 60898 breaker, then if your loop is < or = to 1.20, it will be OK. If it is not, an increase in CSA may comply.

But it is not ideal to run a socket off a different circuit. It causes confusion. Marking the socket will help.

 

[skybluescooby]

Varies responses, hmmm
I tried to discuss the topic of removing floor boards or channelling out walls to the missus last night, tell you what guys, got to watch the Barcelona game in total silence.
Anyway, the max length from garage ring to bedroom would be no more than 15 mtr, the garage has a separate fuse as does the downstairs sockets and upstairs sockets, If my initial post is the only option then i would encase where poss in conduit and mark the faceplate with "Garage ring main", after all there will be a tv plugged in it and nothing else and it'll be 6 ft high.

 

[securespark]

So, did you try my suggestion?

 

[skybluescooby]

Not yet, that is my next step. Thanks for the advice

 

[philrosenberg]

If you do run from the garage I would also put a label inside the box somehow. This means that if a future owner replaces the socket face and fails to label it then there is still some warning there. Maybe if you start the label with "safety notice, not to be removed" it might discourage someone from removing it.