Metal all the way, no brainer

[Andy78]

speaking as a Kiwi, it beat me why you Brits insist on metal domestic boards. We've been using plastic boards for over 30 years without any significant issues. When I started working in the UK 2008 it felt as though I had dropped back into the dark ages. I reckon plastic is superior and much much easier to use. Metal boards are a pain in the a**e down by the sea

Metal boards are a recent change and most domestic installs used plastic boards for years. The change was due to a response by the regulation makers to a request by the London fire brigade to mitigate the perceived increase in house house fires starting in consumer units.
I much prefer to work with metal boards these days but do agree that a well installed plastic board is no risk whatsoever.

 

[Lucien Nunes]

Nothing is infallible. Even a well-installed electrical equipment has failure modes that can generate heat, and where many high-current devices are concentrated together there is an increased probability of enough heat being generated to start a fire. The probability is still low and the risk still small, but where it can be mitigated at modest cost with a genuinely non-combustible board (i.e. not just flame retardant,) and there is no additional risk from using metal, why would you not?

Where a metal board adds the risk of becoming live in a TT install where the Ra is too high to protect the tails, that is a different matter of balancing the two risks.

 

[Deleted member 26818]

A few years ago, there was a class action law suit against UKPN because of a number of fires (5) which started in metal cut outs.
The basis of the law suit, was that UKPN had been negligent in not replacing the cut outs in line with their own maintenance schedule.
To my mind that was a mistake.
The y should have based the case simply on the fact that it was UKPN’s equipment which caused fires endangering people and damaging their property.

Now we have to change plastic CUs to metal, because the equipment inside is so poorly designed and constructed that they are now a fire risk.
Rather than tasking the manufacturers with producing safe equipment, change the Regulations so that the consumer has to take measures to safe guard against the dodgy equipment.

 

[SparkyChick]

A few years ago, there was a class action law suit against UKPN because of a number of fires (5) which started in metal cut outs.
The basis of the law suit, was that UKPN had been negligent in not replacing the cut outs in line with their own maintenance schedule.
To my mind that was a mistake.
The y should have based the case simply on the fact that it was UKPN’s equipment which caused fires endangering people and damaging their property.

Now we have to change plastic CUs to metal, because the equipment inside is so poorly designed and constructed that they are now a fire risk.
Rather than tasking the manufacturers with producing safe equipment, change the Regulations so that the consumer has to take measures to safe guard against the dodgy equipment.

It's not just CU's... consider the situation we have regarding fusing down fans. When I designed electronics that were going into machinery I always included local fusing on the boards. I've got a job to do next week where I've installed a bathroom fan and the manufacturer wants both permanent live and switched live fused down, so I've got all the headache of splitting the bathroom lighting just to comply... all for the sake of less than a quid in parts.

It grinds my gears somewhat!

 

[Deleted member 26818]

Surely, fusing the permanent live before the switch would achieve this?
FCU, feed to fan isolator and a feed to the light switch.

 

[SparkyChick]

I know it's simple enough, but it's time and materials consumers are paying for instead of having manufacturers produce equipment that is inherently safe due to protection within it.

 

[spark 68]

Exactly, the manufacturers know fine well how their product will be connected in the real world, they are simply penny pinching by requiring external fusing down that should have been provided for within the product in the first place.
To me they should not be fit for purpose imo. RE: the bathroom fan in the post above^^^

 

[Wilko]

I finished my first 100m of 2mm sleeving not so long ago. I thought of Westward when I picked up the replacement. I've got a couple of hundred metres of 3mm, not sure I'll ever use it now...

I use it in the garden now.

 

[Blissof89]

I much prefer working with a metal DB and I fully agree with the AMD 3 changes.

Its not just about bad workmanship, switchgear can fail and cause a lot of heat.

A plastic unit melts when it gets too hot and all of a sudden the existing fire is fed a load of oxygen and it grows as that was the only thing it was lacking before, eventually becoming too large to extinguish . A metal unit contains the fire, hopefully until the supply OCPD operates and the fire starves itself or the fire is noticed, isolated and extinguished. There is little chance for the fire to grow as although it has plenty of fuel and heat there is a very limited supply of oxygen inside the fireproof enclosure, and that isn't suddenly going to change.

Its just risk management, yes you could (and should) crack down on the manufactures and regulate who is fitting consumer units but that is a mammoth task in itself and does not guarantee anything. Fire rated enclosures greatly reduce the risk in the event of a failure and there is no arguing that.

Now metal enclosures on TT systems is a whole other problem, my only suggestion would be a metal enclosure that is double insulated via a plastic coating of some sort but idk how feasible this is.

 

[Midwest]

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.

 

[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.----------/wiring-matters/issues/56/fire-protection-panel-discussion-1-at-the-elex-show-in-harrogate/