CU change pricing?

[EFLImpudence]

My understanding is that no plastics can meet this requirement.

Maybe not in its 'raw' state but there may be a process to make it compliable.

In RF's video the wood seemed to do quite well.
Obviously is wood not non-combustible by itself.

 

[JohnW2]

I hesitate to comment on this "emotional" thread, but I wanted to point out the existence of a definition of "non-combustible" in BS-476 part 4. Perhaps the new regs refer indirectly to this?

I don't really know what you mean by 'indirectly', but the new reg certainly doesn't refer to it. BS7671 does refer to BS-476 twice, once in 526.5(iii) (relating to terminations and joints in live conductors) and 554.4.1 (relating to 'heating conductors'), but is not mentioned in 421.1.201.

Perhaps they intended to do so but forgot?

Who knows, but I doubt it - as you go on to say, if that's what they intended, they might just as well have said 'metal only' - which they didn't say.

I don't know (or care much), but thought you might be interested in the BS-476 definition. It requires that a 40x40x50mm lump of the material be placed in a furnace at 750C. It is deemed non-combustible if it does not flame or reach a temperature more than 50C above the furnace temperature. ... My understanding is that no plastics can meet this requirement. Metals, plasterboard, stone etc. are the only things that will.

As above, that's why I doubt that they intended to cite BS476. Plasterboard must surely 'flame' at least for a while, as the paper covering burns away?

Kind Regards, John

 

[securespark]

Can you post a link to RF's vid please?

 

[ban-all-sheds]

Quick experiment to see which CU materials are flammable using three wylex consumer units. One metal, one wooden and one plastic.

OMG

Have I got to remove everything from my house which will ignite if I train a blowtorch flame on it, or only the items where I am reasonably likely to do that?

Please advise, lest I have trouble sleeping. In a bed made from wood and with polycotton bedding.

 

[ban-all-sheds]

Can you post a link to RF's vid please?

Go back up to post #88

 

[JohnW2]

My understanding is that no plastics can meet this requirement.

Maybe not in its 'raw' state but there may be a process to make it compliable.

Who knows, but I would seriously doubt it - 750°C is a very high sustained temp for any 'plastic'. IIRC, even thermosets like Bakelite only have an ignition temp of 450-500°C. However, as I've just written, I doubt that 421.1.201 intended to reference BS476.

Kind Regards, John

 

[ban-all-sheds]

Obviously is wood not non-combustible by itself.

It is actually pretty fire-resistant and non-propagating by itself.

Wooden structures often perform surprisingly well in fires - what happens is the outside of the wood chars, and that layer protects what's underneath.

 

[endecotp]

Plasterboard must surely 'flame' at least for a while, as the paper covering burns away?

BS 476 part 4 allows for a small amount of flaming - I think 10 seconds - which I presume is to allow for surface finishes e.g. paint to burn off. But I should perhaps have written "gypsum" rather than "plasterboard" in my previous post.

 

[endecotp]

My understanding is that no plastics can meet this requirement.

Maybe not in its 'raw' state but there may be a process to make it compliable.

I really don't think so. The specs for e.g. brominated ABS, as used for "flame retardant" electrical enclosures, and the materials used in PCBs, don't come close to the BS 476 part 4 requirement.

If your googling skills can find something, I'd love to see it.

 

[skenk]

Surprised at how quickly and easily the Wylex plastic CU ignited in RF's vid. It would be interesting to see how standard plastic switches and sockets compared (my feeling is they would be more robust).

 

[JohnW2]

Surprised at how quickly and easily the Wylex plastic CU ignited in RF's vid. It would be interesting to see how standard plastic switches and sockets compared (my feeling is they would be more robust).

The brittle (and 'orrible to work on!) material which most (other than PVC back boxes) electrical accessories are made out of (some sort of thermosetting urea-formaldehyde resin, I think) is pretty fire resistant (scorches, but doesn't melt and rarely 'flames'), quite possibly enough to satisfy BS7671's undefined requirement for CUs - but people would probably be shattering them all over the place if they had to drill holes in them.

Kind Regards, John

 

[Iggifer]

What about the boxes that smell like a certain illegal plant when you drill them?

 

[JohnW2]

What about the boxes that smell like a certain illegal plant when you drill them?

I'm not sure which ones (boxes!) you're talking about. Standard ones usually smell of fomaldehyde if you drill, saw, file or machine them.

Kind Regards, John

 

[Iggifer]

I'm not sure what type they are, but they're somewhere in between the explosive boxes, and the super flexible ones.

To be honest, I'm not even sure I would know what formaldehyde smelt like - maybe we're talking about the same smell, but your olfactory memory associates it with the closest thing it knows (I don't partake in said plant, just thought that needed clearing up)

 

[securespark]

(I don't partake in said plant, just thought that needed clearing up)

You don't partake but know its smell well....