wiring a ring in 2.5 is no longer acceptable?

[willelec]

So my boss had the NIC inspector out the other day and he mentioned that wiring a ring in 2.5 is no longer acceptable. He stated that even wiring a ring in 4mm is now pushing it when it's installed in insulation.

We have always wired rings in 4mm as we wire large holiday homes. All my other sparky mates use 2.5..

I'm just wondering if anyone else has had this said to them and if it's just the NIC being really picky as usual.

 

[The Ghost]

So I suppose we should use 6mm² instead then. So even if calcs show it is ok, then it's not according to NICEIC. Lets get rid of BS7671 then and just phone NIC to see what we should do in every circumstance. A shame that a ring circuit is no longer "deemed to satisfy" (NIC)

 

[Wilko]

Hi Will. and welcome to the forum !
Maybe they are talking about the effect of insulation? The cable for a 32A ring must have a rating of at least 20A and for cable floating loose in a cavity wall with insulation the 2.5mm is only 13.5A (Table 4D5, method 103). Even 4mm is only 17.5A. So either 2.5 or 4mm can work for a ring, but insulation can spoil it ...

 

[PEG]

Hi,wiring a ring final circuit,in 2.5 is perfectly acceptable.

Applying other factors,to that circuit,such as external influences,grouping,temperature,etc,is also acceptable.

Taking the two statements,separately,is not acceptable.

I hope NICCY,find my explanation...acceptable

 

[Octopus]

If the NICEIC want to make sweeping statements they need to back them up with facts from BS 7671

 

[Pat H]

Surely it depends on the installation method and the rating of the MCB?
Nowadays ring mains often aren't required to carry 32A so if on a 20A breaker or even a 16A then 2.5mm maybe ok.
Its all down to the calculations.
I've just done a ring main for a loft conversion but was able to minimise the cabling contact with insulation. So it was largely surface mount in free air. But if it has to go in wall and be completely insulated then it depends on the calcs and the current required.

 

[westward10]

I suspect there are some crossed wires here with regards as to what the inspector said.

 

[Octopus]

I suspect there are some crossed wires here with regards as to what the inspector said.

Are they 2.5 mm or 4 mm?

 

[Pat H]

Harmonised or not wires?

 

[Wilko]

I'm waiting for the 18th where 802.11 is included, I heard ...

 

[hightower]

I've just done a ring main

Oooo, don't let @Pete999 hear you call it that.

 

[Chr!s]

So my boss had the NIC inspector out the other day and he mentioned that wiring a ring in 2.5 is no longer acceptable. He stated that even wiring a ring in 4mm is now pushing it when it's installed in insulation.

We have always wired rings in 4mm as we wire large holiday homes. All my other sparky mates use 2.5..

I'm just wondering if anyone else has had this said to them and if it's just the NIC being really picky as usual.

Hi, well is insulation is involved then yes he's right, it derate's the cable.

 

[Andy78]

Plenty of ways to avoid this problem through proper design rather than making up blanket rules for numpties who don't ever do a single cable calc.

 

[Pat H]

Oooo, don't let @Pete999 hear you call it that.

I've got fed up calling it a RFC and customers asking whats that. Easier to call it a ring main and they know what I mean.

 

[7029 dave]

I would love to see anybody fighting anything more than 4mmx2 into the back of a socket. lol