Metal all the way, no brainer

[Pete999]

When the new reg for metal CU’s came in, Certsure web in air vid, with that Darren Standforth what’s his name, said the idea behind the change was to remove a source of fuel (i.e. the plastic enclosure) from a fire. Then they changed the reasoning to containing a fire.

From that op pic, think the former was better reasoning, if at all.

The new reg is for CUs constructed from noncombustible materials, just so happens that metal is noncombustible, or in a noncombustible enclosure.

 

[Blissof89]

I guess a metal enclosure both removes the fuel and the oxygen from the fire equation, but I'm fairly sure the core principles behind a metal enclosure is to remove oxygen. There will always be fuel in the way of plastic casings for breakers and cable insulation.

OP's pic is kind of a moot point as the fire started outside the enclosure

 

[Midwest]

Yeah but the enclosure cover has been consumed by the fire, whereas the cabling & switchgear has to, but to a lessor extent. I recall reading somewhere, switchgear, the MCBs etc, are manufacturered from a different grand of ‘plastic’.

 

[johnduffell]

Cus are not designed to keep a fire in or out. Obviously metal is less meltable than plastic but i don't think that was part of the intention of the change in regs.

 

[Midwest]

I don’t know. Whether it was to contain a fire, remove a source of fuel? Presumably there was a reason to switch from plastic to metal.

 

[Blissof89]

Of course a metal enclosure is suppose to limit the spread of fire, why do you think people call them fire rated? As Midwest said, there is a reason we stopped using plastic.

The intent of regulation 421.1.201 is considered to be, as far as is reasonably practicable, to contain any fire within the enclosure and to minimise flames from escaping, caused mainly as a result of poorly installed connections

 

[andysparkfree]

Thinking about it a bit more, if a fire is so close to a fuse board, i think metal or plastic, i wouldn't want to be touching it.

 

[Midwest]

Dunno if you've watched this vid? Whilst they don't suggest metal CU's are supposed to be fireproof, nor remove source of fuel, and its bit old guidance by now, still interesting vid about metal CU's back then. Sound needs adjusting at beginning.

Fire protection: panel discussion 1 at the ELEX show in Harrogate - https://electrical.------.org/wiring-matters/issues/56/fire-protection-panel-discussion-1-at-the-elex-show-in-harrogate/