Which CU ? Decisions, decisions ...

[JohnW2]

I suspect that smoke will leak out, even if fire is contained. And assuming there is a suitable smoke detector located nearby, then that will trigger on quite small amounts of this sort of smoke - I'd have thought.

"Maybe" to all of that! What with glanding of cables etc, if the front cover seals fairly well (which it presumably has to if it is to act as an effective fire barrier), I'm not sure that I would want my life to depend upon significant amounts of smoke getting out particularly quickly, and finding its way to the nearest smoke detector. A requirement for a mini smoke detector within a ("combustible") CU might actually be a better option!

But yes, you do make a valid point. There's not much benefit to having (say) a 1/2 hour fire resistance if it delays the alarm sounding by 1/2 hour

Quite so!

EDIT: Really, while I agree with you that the regs are "wrong", debating that is just being pedantic for the sake of it. It doesn't matter how much we debate what is wrong with the regs, they are there as written and I can't see that changing. So I suggest we just accept that and move on. ... Yes, complain to whoever is responsible for the cockup, but just stop arguing that it's currently not possible to fit a CU in compliance with the regs. I think we all agree - but most of us agree that there is a pragmatic approach that allows the world to carry on while we wait (for a long time) for the buffoons to sort out the mess.

Exactly.

Kind Regards, John

 

[Iggifer]

I would go for in order:

Eaton
Hager
Schneider

Would Echo RF's comments about Merlin Gerin withstanding all kinds of abuse, however, the DIN rail clips on the old Multi9 devices were a bit rubbish, they tended to go brittle and break. And also his comments about Eaton being harder to get, they're not impossible, but unlikely to be able to get them off the shelf like hager.

Hagers amd 3 boards are great for RCBOs, much more headroom than before.

 

[JohnW2]

Maybe the regs. should be amended to something more specific, such as stating that casings should be of steel no less than such-and-such thickness?

Indeed - I think everyone is agreed that the regulation should be far more specific (and 'possible to comply with').

The present reg is a bit like requiring conductors to be insulated with a 'non-conducting' material. Just as is the case with 'non-combustible', 'non-conducting' is also impossible - and if a regulation called for that, no-one would have a clue as to what degree of 'insulating properties' the material was required to have.

Kind Regards, John

 

[stillp]

stillp, if you're listening ... do you have any information (or even just vague rumours) as to when the next consultation on BS7671 is likely to happen?

No, sorry. I'll probably be notified when it does though.

 

[JohnW2]

stillp, if you're listening ... do you have any information (or even just vague rumours) as to when the next consultation on BS7671 is likely to happen?

No, sorry. I'll probably be notified when it does though.

I feared so. If/when you do get notified, I'm sure that there would be a few ears around here that would welcome being whispered into

Kind Regards, John

 

[stillp]

I'll do more than whisper!

 

[kai]

I noticed that MK breakers have a type of finger operable din-rail clip, where I could use my finger gently applied against the lower din-rail clip, sliding it down to remove it from the MK din-rail, without the need for a small flat screwdriver.

 

[Iggifer]

I noticed that MK breakers have a type of finger operable din-rail clip, where I could use my finger gently applied against the lower din-rail clip, sliding it down to remove it from the MK din-rail, without the need for a small flat screwdriver.

Hager are the same, if not considerably better. It's a 2 part design. Eaton/MEM used to put them at the top (that was SUPER convenient) but have now changed back to the standard bottom style.

 

[ban-all-sheds]

1) "But the official advice on the matter specifically says that a steel enclosure is non-combustible and meets the regs - so how do you justify claiming that it doesn't comply with the regs ?"

"Deeming" a material to have a physical characteristic which it does not will not magically imbue it with that characteristic.

I agree, but in the meantime, there is a set of regs, in print, to which Building Control will expect compliance. For those sparkies in one of the approved bodies, I believe their membership requires compliance with the regs.

So how do they comply with a requirement which is impossible to comply with?

Given that I'm sure this has already been raised, and nothing has been changed - I think it's safe to assume that no official "clarification" is going to come out soon. So people either adopt a pragmatic definition of non-combustible (that is also in line with other regs where similar wording is used)

One pragmatic approach would be to carry on fitting CUs made of plastic which passes the sorts of fire-related tests which plastic used for accessories and enclosures has had to pass for years.

EDIT: Really, while I agree with you that the regs are "wrong", debating that is just being pedantic for the sake of it. It doesn't matter how much we debate what is wrong with the regs, they are there as written and I can't see that changing. So I suggest we just accept that and move on.

That is wrong.

Yes, complain to whoever is responsible for the cockup, but just stop arguing that it's currently not possible to fit a CU in compliance with the regs. I think we all agree - but most of us agree that there is a pragmatic approach that allows the world to carry on while we wait (for a long time) for the buffoons to sort out the mess.

The pragmatic approach would be to carry on fitting CUs made of plastic which passes the sorts of fire-related tests which plastic used for accessories and enclosures has had to pass for years.

 

[SimonH2]

Maybe the regs. should be amended to something more specific, such as stating that casings should be of steel no less than such-and-such thickness?

No, they should not specify materials or construction - that is always a bad way to legislate. Compare with cars, ignoring VW (and the others that haven't been caught yet), emissions standrds should be as simple as "here are the limits, meet them in any way you can". Instead we (EU) mandated certain technology (cats) which immediately killed off other avenues that were under development. That's not to say the other avenues would have worked (lean burn had it's own problems) - just that the legislation f***ed things up by dictating the how, not the what.

For an example of a better way of doing it, the building regs don't dictate what insulation etc should be used - only the thermal performance of a new build. It's then for the designer to trade off the options - eg if they want more windows, they need to have better insulation in the walls and roof. If they are happy with smaller windows, they can get by with thinner walls.

What they should do is specify what level of "non-combustible" is required. Either in terms of (preferred) "to schedule X of standard Y" or in terms of "able to withstand X˚C for Y minutes without impairment of structural integrity". From previous conversation, I vaguely recall mention of existing standards - all it would require is to pick one and specify it.

it would (or at least should) be fairly easy for the committee to admit they f***ed up on this, and simply issue an amendment to amendment 3 clarifying what "non-combustible" means. That might upset a few people if they find that their "amendment 3 compliant" products don't actually comply with the imposed standard - but then (as BAS points out) they don't technically comply now anyway, they only comply to a "pragmatic" interpretation of what Amdt3 ought to say.

 

[JohnW2]

What they should do is specify what level of "non-combustible" is required. Either in terms of (preferred) "to schedule X of standard Y" or in terms of "able to withstand X˚C for Y minutes without impairment of structural integrity". From previous conversation, I vaguely recall mention of existing standards - all it would require is to pick one and specify it.

I think that, as previously discussed at length, therein lies one of the (many) confusions. 421.1.201 requires compliance with BS EN 61439-3 - which, I believe, includes requirements in relation to fire resistance/'combustibility'. However, it then goes on to say "... AND SHALL HAVE their enclosure manufactured from non-combustible material, or ..." - which seems to imply that there is a requirement in relation to 'combustibility' which goes beyond the requirements of the cited Standard - but without any indication of what those 'additional requirements' actually are.

Kind Regards, John

 

[ban-all-sheds]

Maybe it's simply that they meant to write 'or shall have their enclosure....'

 

[stillp]

No, I think the LFB were dissatisfied with the requirements of 61439-3. This was discussed at an IET seminar recently, in which it was stated that 61439-3 requires the plastic material to be self-extinguishing, which allows it to continue burning while the ignition source is still present.

What they're going to do about the body of the MCBs is anybody's guess.

 

[JohnW2]

No, I think the LFB were dissatisfied with the requirements of 61439-3. This was discussed at an IET seminar recently, in which it was stated that 61439-3 requires the plastic material to be self-extinguishing, which allows it to continue burning while the ignition source is still present.

Did the LFB then not indicate what (achievable!) criteria (beyond those required by BS EN 61439-3) they did want to be satisfied, so that this could be specified in BS7671?

Kind Regards, John

 

[stillp]

As we've discussed previously, I don't know, I wasn't there. Presumably not.