CU, head and meter enclosures fire resistance

[frank999]

Hi,

Question relates to a flat conversion.

Does a metal cased CU on a 60 minute fire resisting separating wall need to be installed inside a certificated fire proof enclosure, or can it be enclosed in a hand made cabinet made of Fire Rated ply or MDF.

Similar question for the main DNO's head, and suppliers meters, although these do not sit on a separating wall, can these be boxed/enclosed using fire rated ply/MDF.

Thanks

 

[RF Lighting]

A properly sealed fully metal CU with self closing flap over the front is all that is required.

There are no requirements regarding the meter / cutout.

You can build a wooden cupboard around them as long as you leave enough room to service & repair the equipment

 

[Adam_151]

A properly sealed fully metal CU with self closing flap over the front is all that is required.

Where does the requirement for a self closing flap come from....it only seems to appear in manufacturer's literature

 

[JohnW2]

A properly sealed fully metal CU with self closing flap over the front is all that is required

I haven't seen any requirements for CU enclosures to provide any fire 'containment'. The only regulation of which I am aware states that it has to be made of 'non-combustible' material. Unless there is some other reg of which I am unaware, the entire CU enclosure could be full of holes as big as the required IP permitted (e.g. mesh made of ferrous metal) and still be compliant, provided only that the material (between the holes ) was 'non-combustible'.

Am I missing some other regulation?

Kind Regards, John

 

[RF Lighting]

I assumed it must be one of the requirements of BS EN 61439-3 as all the “18th edition” CUs I’ve seen are designed in this way. Perhaps as you say it’s one of those things which has become the norm, without actually being required.

 

[JohnW2]

I assumed it must be one of the requirements of BS EN 61439-3 as all the “18th edition” CUs I’ve seen are designed in this way. Perhaps as you say it’s one of those things which has become the norm, without actually being required.

I don't know what BS EN 61439-3 has to say about it (can anyone tell us??) but, as I implied, BS 7671 appears to be only interested in the material, not about it having any ability to contain fires.

However, it seems that prior to BS EN 61439-3:2019, the previous most recent version was BS EN 61439-3:1991 - obviously long before BS7671 required 'non-combustible' CUs.

Kind Regards, John

 

[AndyPRK]

Manufactures make them with metal lids and they have to default to closed to prevent fire out the front.

No point having a metal enclosure with a massive gap at the front.

 

[frank999]

Thank you for the replies, the question was more about the location, and boxing in of a CU, rather than the CU's construction itself.

The Location is by the entrance door to a flat, which is a protected escape route, the CU will sit on a 60 minute Fire Separating wall adjacent.

"You can build a wooden cupboard around them as long as you leave enough room to service & repair the equipment"
I've been advised to box in using fire rated materials, plaster board for example, ideal for cable runs, but a CU will need a cabinet with hinged door - for easy access would be done using wood, but again fire rated sheet materials, such as ply or MDF.
Am I correct to think a CU if mounted on ply, MDF or chipboard, then that should be fire rated, but does that apply to any cabinet/enclosure of the CU itself.

 

[JohnW2]

Manufactures make them with metal lids ...

They do. If it has a lid, then it presumably has to be made of 'non-combustible' material in order to comply with BS7671.

... and they have to default to closed ...

That is what they appear to believe is required, but I have no idea where it comes from. As has been suggested, it's possible that BS EN 61439-3 says something about this (but does it not also apply to plastic CUs?), but BS7671 certainly doesn't.

... to prevent fire out the front. .... No point having a metal enclosure with a massive gap at the front.

Very little point, I agree - but, as I said, at least as far as BS7671 is concerned, there seems to be absolutely nio required for fire 'containment' (e.g. "not having a massive gap at the front"). It would appear that the front, sides and bottom of a CU enclosure made of steel which had numerous 11mm diameter 'ventilation holes' (or even steel mesh with 11mm holes) would be compliant with BS7671.

As well as being arguably 'unnecessary', the BS7671 regulation appears to have been very poorly thought through, and is certainly very badly worded.

Kind Regards, John

 

[JohnW2]

I've been advised to box in using fire rated materials, plaster board for example, ideal for cable runs, but a CU will need a cabinet with hinged door - for easy access would be done using wood, but again fire rated sheet materials, such as ply or MDF.
Am I correct to think a CU if mounted on ply, MDF or chipboard, then that should be fire rated, but does that apply to any cabinet/enclosure of the CU itself.

I am unaware of any regulations which require any of what you suggest. Enclosing CUs etc. in wooden cabinets is common.

Kind Regards, John

 

[aptsys]

Manufactures make them with metal lids and they have to default to closed to prevent fire out the front.

No point having a metal enclosure with a massive gap at the front.

The consumer unit is not required to be sealed in any manner other than to satisfy the requirements of IP ratings. The enclosure is not designed to form a fire barrier or suppress a fire, it's simply there to not catch fire or melt.

Similarly, there is no requirement for metal. Simply non-combustible and passing the glow wire test.

 

[frank999]

Thank you for the reply.

Enclosing CUs etc. in wooden cabinets is common.

That was my impression of matters.

I am sure my Fire Risk Assesor has mentioned that where timber is used in such a manner to enclose, it should be fire rated, I will go back and ask.

 

[EFLImpudence]

Well, he might say that because he is a Fire Risk Assessor but that doesn't mean it is a requirement by any regulations.

What about the stairs?

 

[frank999]

Stairs ? one fo the CU's will be near to a staircase ... and part of the esacape route.

FRA - so he does not have any jurisdiction over the electrical installation ?

passing the glow wire test
I remember when Polystyrene was a novel product, people glued it to ceilings, and cut shapes out of it, using a hot wire.

In a domestic setup - in what circumstances would a 1.5 or 2.5 copper cable be likely to glow red, I am sure it happens, hence why they changed CU's from plastic to metal, just curious for some examples.

 

[JohnW2]

I am sure my Fire Risk Assesor has mentioned that where timber is used in such a manner to enclose, it should be fire rated, I will go back and ask.

As has been said, that's the sort of thing one might expect a Fire Risk Assessor to say!

Does he believe that all, or virtually all, of the timber the house/flat should be 'fire rated', since much/most of it will be in the vicinity of, and/or 'enclosing', things electrical (like cables) and/or potential sources of heat/fire (any electrical appliance/equipment!)?

Kind Regards, John