Class 2 consumer units

[Evans Electric]

Anyone spotted this gem in the OSG ?

Class2 boards recommended for TT installs.     Don't think Denmans are selling those.

Page 20.

And can I ask how we are expected to fireproof all entries ,   tails in those 3 way stuffing glands , what about the other holes ?  How about the knockout that we didn't need in the end ?   Do we weld a steel plate  on   ?

 

[SLIPSHOD & SLAPDASH]

I noticed that only on Friday. Did you also notice on page 21  (b) is referring to  reg 416.22 & 416.22.1. I have had a good look through my reg book & cant find those.

 

[Andy™]

class 2 board... so OSG is recommending plastic? must have a look at that, never really looked in OSG

no need to fireproof cable entries, it only says the enclosure should be non-exploding

 

[SLIPSHOD & SLAPDASH]

no need to fireproof cable entries, it only says the enclosure should be non-exploding

That's why i was looking through it on Friday. My colleague was saying the entries had to be fire proof as the OSG said it. I think he saw the 'In all cases' before the (a,b,c) but i read that as all cases of TT   ?

 

[NozSpark]

IIRC it does say that you should minimise the size of any cable entries though,,, but not fire proofing

 

[Evans Electric]

Thats why I looked TBH ..... someone saying the exit holes need to be fireproofed.

 

[Essex1]

The OSG is not BS7671.  Entry holes do not need to be 'fire proof' and neither does the CU. The entry holes just need to be sealed. Plastic trunking is acceptable. 

 

[Evans Electric]

So that knock out you don't need .........  in most steel enclosures with a spare hole I usually stick a 20mm blind grommit in TBH ...so these big square holes we ...what ... jam a piece of exploding YT4 in there ?  Come on .. they'll have to be plated over for when the inferior components & the loose terminals go into meltdown.

With an industrial board , if you removed, say, some 3x3 trunking  from it , you'd have to plate the hole over.  Same here .

Are you interpreting that Ins. & sheathed cables can only enter the new domestic boards via plastic trunking ?       Many existing installs have cables clipped surface down wall to CU .

 

[Andy™]

you only need to maintain its IP rating... so that bit of trunking over the top for the cables,  which just happens to cover that extra hole you made, would comply

 

[Essex1]

I think the easiest way to comply is to have a piece of 50x50mm trunking running horizontally at the top of the CU. 

 

[kerching]

So In essence we have a non combustable enclosure with holes in it that are sealed with a flammable material?

seems like a plan to me

 

[Andy™]

great planning, isnt it?

 

[Essex1]

The whole thing is stupid but it is what it is. 

 

[Andy™]

dont worry though, next amendment will be all wiring must be unsheathed pryo with correct glands into CU, avoiding any holes or anything explosive around it

 

[binky]

if the cable entries are resonably well sealed then any fire within the CU will self extinguish by lack of oxygen. However, Essexs' trunking solation could allow smoke egress and oxygen ingress?? Though he is totally correct in saying it complies. Half baked proposal if you ask me, all glands should be those posh metal ones to make the enclosure proper fre rated, or cable entries filled with intumescent material.

 

[dmxrr]

dont worry though, next amendment will be all wiring must be unsheathed pryo with correct glands into CU.

I hope so, that would get rid of the chancers in the industry. 

Pyro installs are the most satisfying jobs in the trade IMO

 

[ProDave]

The OSG is not BS7671.  

No, but it's meant to be clarification of what 7671 actually means. So in a court of law, you were just taking that guidance.

 

[Essex1]

if the cable entries are resonably well sealed then any fire within the CU will self extinguish by lack of oxygen. However, Essexs' trunking solation could allow smoke egress and oxygen ingress?? Though he is totally correct in saying it complies. Half baked proposal if you ask me, all glands should be those posh metal ones to make the enclosure proper fre rated, or cable entries filled with intumescent material.

This is the problem. Not using the correct terminology. The regs do not say the enclosure needs to be fire rated. Just manufactured of NC material.  

We we all need to stop looking so deep into the reg and just crack on with installing steel CUs (until a plastic NC CU is released) and make sure the cable entries are well sealed with a trunking or something similar.  The lid needs to also be NC but it does not matter which way the lid hinges. 

The CU does not need to be fire proof, flame proof or anything like that. 

We we all need to get over it and move on. 

 

[ProDave]

This is the problem. Not using the correct terminology. The regs do not say the enclosure needs to be fire rated. Just manufactured of NC material.  

We we all need to stop looking so deep into the reg and just crack on with installing steel CUs (until a plastic NC CU is released) and make sure the cable entries are well sealed with a trunking or something similar.  The lid needs to also be NC but it does not matter which way the lid hinges. 

The CU does not need to be fire proof, flame proof or anything like that. 

We we all need to get over it and move on. 

Except the previous generation of CU's were supposed to be non combustible, only the manufacturers have now admitted they in fact were not.

The sooner someone buys my house and I can retire the better.

 

[Essex1]

No, but it's meant to be clarification of what 7671 actually means. So in a court of law, you were just taking that guidance.

I would not agree with that. I think it is a 'quick find' guide to all the most relevant regulations in domestic new builds written in easier to understand language. 

It helped me when I was fresh out of my time but I would not bother with one now. Too many learners are not familiar enough with the regs and these 'guides' only keep them further away from becoming familiar with BS7671. 

The OSG has no information of any use whatsoever outside of domestic electrical work.