radial from ring main

[jaresquire]

I think it's more a bad practice thing, can't think of the downside compared to a true ring except for testing and it's not the worst real world crime you find in most domestics of some age.
Wouldn't do it by design thou.

 

[chiplard]

IT IS NOT ALLOWED IN ACCORDANCE WITH BS7671!!!

END OF!!

It worries me when people come out with excuses as to why it wouldn't be a problem. Irrespective of how safe people think it is, what current might flow, what the load is etc etc. It is not an allowable method.

What else would people do in their own judgement of what is safe?

 

[jaresquire]

Ok, had a bit of a read of the brb, the issue seems to be;
Once the 4mm spur added, circuit is not a ring-final by definition, therefore need to be able to defend design, which is complicated because;
Need to consider the ring section as two conductors in parallel - requirements are balanced loading and no branches, so very careful examination of existing ring required.
Because of this I accept best to just extend ring or use fused spur.
Thats my humble pie for 2011

 

[marky sparky]

unfused spurs should only have 1 single socket running from them .ref 17 edition

 

[nickblake]

me i would stick a fused spur on it and wire in 1.5mm if its for just a couple of sockets in a bed room

 

[jaresquire]

"unfused spurs should only have 1 single socket running from them .ref 17 edition "


Not as simples as that, there are other circuit configs apart from ring finals eg radials where you can spur off multiple sockets. The standard ring in Appendix 15 is a guide that saves some head scratching as long as you stick to all the restrictions.

 

[nick611]

no thats unfused spurs in 2.5 not 4mm,this adition is not coverd in regs.so how can you know its not allowed?

 

[nick611]

IT IS NOT ALLOWED IN ACCORDANCE WITH BS7671!!!

END OF!!

It worries me when people come out with excuses as to why it wouldn't be a problem. Irrespective of how safe people think it is, what current might flow, what the load is etc etc. It is not an allowable method.

What else would people do in their own judgement of what is safe?

its not considerd in 7671 so how can you say its not allowed?quote me a reg that forbids it

 

[JulianC]

I think the only thing you'll find on this is in the on-site guide, 8.2.4 - "In an A1 ring final circuit.....a non-fused spur should feed only one single or one twin socket outlet"

However, given that the point of the fuse in a fused spur is to protect the cable in the spur, and, subject to installation conditions, 4mm can handle more than 32A and will therefore be protected by the 32A breaker protecting the ring, I am struggling to find a problem with what you are suggesting nick611. As you say, it is not considered in BS7671.

Mind you, I have been at the port.....

 

[Risteard]

I am struggling to find a problem with what you are suggesting nick611. As you say, it is not considered in BS7671.

It is not permitted because it would adversely affect the balancing of the ring.

 

[JulianC]

Aah, the mystical dark art of ring balancing. Not convinced. Where does it say it's not permitted? (playing devil's advocate)

 

[kmcgold]

u can spur off has many sockets has you like if you have fused it down to 13amps and the zs value of the circuit are ok
if no fuse then only one socket etc even if you used 6mm still only one socket etc

 

[kmcgold]

(risteard said It is not permitted because it would adversely affect the balancing of the ring.)

correct.

 

[jaresquire]

Not convinced of this ring balancing either, as we are talking of the same load at the same point of the ring, just different wiring method downstream.
Why am I defending something I've never done though?

 

[JulianC]

Just 'cos we've never done it, nor considered doing it, doesn't mean it's not right! Rather than blindly reading and (mis)interpreting the regs. it's good to think about these things sometimes.

It's clear that this is not covered specifically in the regs. One the plus side, there are no current carrying capacity problems using 4mm. On the down side there's wonky ring syndrome. Now correct me if I am wrong, but I could fit 4 fused spurs off 4 adjacent sockets quite happily and 'correctly' and unbalance me ring.