Ring final power circuit, where every socket is supplied from junction box is a spur

[flyingspark]

Hello,

I have been asked to rewire a flat, of which the owners dad is an 82 year old retired spark. He wants to help out, to save his daughter (the owner) some money.

I met him at the flat and we had a walk around, he seems to know the installation well as has worked on it over the years. He said the sockets have been wired - (please see my attached diagram), as a ring where most, if not all the socket outlets are fed from junction boxes from a ring.

He wants me to rewire it like-for-like, mainly so that the same conduit embedded in the wall can be used. This conduit is 10mm or 12mm (not 20mm so wont take two lengths of 2.5), The flat has concrete floors, and no access from above the ceiling. I have been thinking long and hard about this and cant decide if its is permissible.

My main questions are -

Would the plug top fuses count as to adequately protect the spur conductors against overload?

Or, would the intended 32A RCBO (currently 30A BS 3036 Rewireable fuses) cover the spurs?

If using mostly Method C, 2.5mm3, the current carrying capacity is 20A, so how are non fused spurred socket outlets normally protected, 433.3.1 I think?

The regs also say that the total number of non fused spurs should not exceed the total number of socket outlets, as there are zero sockets, then purely on that basis alone I think is it a no goer, anyone?

All comments welcome.

 

[ianmacd]

As long as only one double socket (or other accessory) is fed from a JB then this is not an issue as you will have one JB on the ring for every spur.

Watch out for cable direction in the wall. I may be tempted to let him faff about pulling the cable (you supply) though the capping as that will be an arse under your supervision.

 

[Lurch]

Technically I think you'd be fine, but it's an odd way of doing it. Is this 1 ring for the whole flat, no chance of getting it on a 20A, or making a couple or more 20A radials out of it?

 

[flyingspark]

This time with my attached picture (I hope)

I know it sounds odd, it is odd to do it this way! but I am trying not to offend the retired spark, or at least do it his way, if it is permitted.

So a JB could be counted as a socket for the purposes of amount of fused spurs allowed per ring you say?

I am hoping my pic will come up now (forgot to attach with first post)

Cheers

 

[flyingspark]

Great! my example diagram i made is now available (attached to my post above).

I know what you are saying about who pull the cable through, but he is 82 years old, he did say though he would work as my mate!

No, it wont just be one ring for whole flat, the kitchen will be sepperate, I wil know more once i start having a closer look, and remove a few fronts, but think I will be fairly standard to put a ring in the kitchen.

As far as changing it for a radial, i am still faced (except for last socket) with not big enough diamater conduit to get two lengths of 2.5mm t&e through it. Am trying to find a way of doing it without replacing the conduit for 20/25mm. Have also thought about singles, have done the bunching maths yet though.

 

[Risteard]

Due to the fact that there are more unfused spurs than socket outlets directly connected into the ring final circuit (i.e. zero) then it fails to comply with the Regulations.

 

[Lurch]

As far as changing it for a radial, i am still faced (except for last socket) with not big enough diamater conduit to get two lengths of 2.5mm t&e through it.

I meant do it with the junction boxes, but as a radial. Slightly more conventional.

Or put 23 sockets next to the board on one leg of the ring so you have some sockets on the ring so the spurs comply. (Not a serious option BTW)

 

[tom1]

I meant do it with the junction boxes, but as a radial. Slightly more conventional.Or put 23 sockets next to the board on one leg of the ring so you have some sockets on the ring so the spurs comply. (Not a serious option BTW)

 

[ianmacd]

Due to the fact that there are more unfused spurs than socket outlets directly connected into the ring final circuit (i.e. zero) then it fails to comply with the Regulations.

Care to quote the regulation? I think you will find it implies accessories of which a JB is one.

Don;t forget if the JB's are not accessible then they need to be wago's or other method of connection.

 

[ianmacd]

Forget the last bit, just saw your diagram.

 

[Adrian]

be careful with the old split oval tubing as it may be corroded and the rubber grommet perished

 

[flyingspark]

Many thanks to everyone who has contributed to this post, thanked!

With ref. to the circuit design, its inconclusive, I make it 66% ok and, 33% not ok.

Also thanks for the tip re the split conduit.

Any more for anymore?

Thanks.