Consumer unit mounting

[Russell griffiths]

Morning all. 

What type of material should a CU be mounted to, does it need to be non,combustible 

im just putting up stud walls and it would be easier to install whatever I need into this cupboard before I build any more walls. 

Back wall is clad in OSB to stiffen it and for screwing into, what should I put on top as a finish. 

 

Fire line plasterboard 

fermacel 

glitter. 

@ProDave @Nickfromwales @Onoff

[markc]

Yes it should be non combustible. In an installation last year i used a piece of cement board over the standard Chipboard the wall was made of.

Maybe overkill but i have seen CU fires before.

[MikeSharp01]

We used 12mm Hardiebacker board, on 15mm OSB for the Garden room and will use the same in the main house shortly.

[markc]

2 minutes ago, MikeSharp01 said:

We used 12mm Hardiebacker board, on 15mm OSB for the Garden room and will use the same in the main house shortly.

I would do exactly the same, although i have just had another look at the Regs and technically the board isnt needed as the CU is fully enclosed ... i still prefer the added barrier

[ToughButterCup]

Fireline  PB is what we are using.... the remnants of the board not used to line the steels. Plus a bit of fire resistant foam, jobs a goodun. 

[Onoff]

Meter board from CEF. You can also get little spacers for mounting off the wall. Handy for getting cables up behind. 

 

Tbh some CEF branches are better than others. Best to order online for collection at a local store then you can check for lumps knocked off it!

 

https://www.cef.co.uk/catalogue/products/search?q=Meter board

[ProDave]

Standard board in the back of a meter box is very thin chipboard, so it seems no need to be anything particular.

[MikeSharp01]

6 hours ago, ToughButterCup said:

Fireline  PB is what we are using

I find fixing stuff to PB is such a pain that I need some sort of pattress to fix to.

[Carrerahill]

8 hours ago, Russell griffiths said:

Morning all. 

What type of material should a CU be mounted to, does it need to be non,combustible 

im just putting up stud walls and it would be easier to install whatever I need into this cupboard before I build any more walls. 

Back wall is clad in OSB to stiffen it and for screwing into, what should I put on top as a finish. 

 

Fire line plasterboard 

fermacel 

glitter. 

@ProDave @Nickfromwales @Onoff

Technically it can go onto anything! Most new builds mount it on a piece of OSB. There is no direct reg in BS7671 18th - which states the mounting material must be non-combustible. There are a couple of regs, 421.1.? which states that materials used to form enclosures for electrical equipment must be non-combustible or the enclosure must be non-combustible, and it even gives the example of a ferrous metal, in other words, make it in steel and you are exempt from making things out of non-combustible materials. 

 

Now just because the regs say something, doesn't mean they are infallible!

 

So as the consumer unit itself is metal and is supposed to be fully sealed to stop the spread of fire, if the CU's integrity has been maintained, then fire should not be able to escape, so worry more about ensuring the unit is using appropriate glands and intumescent seals etc. 

 

I personally think that it should be on a non-combustible material, I made a board for my unit out of 11mm OSB covered with 12.5mm plasterboard.

Edited August 14, 2020 by Carrerahill

[Nickfromwales]

We're almost always fitting them in plant rooms, and we pretty much always line the plant rooms in 18 / 25mm plywood as there is just so much stuff to affix. CU's with us are straight onto that plywood, and then proper and full attention given to the fire integrity ( spread of fire from inside the CU to it's surroundings ) to maintain the standard.

Yes, it won't hurt to make a nice fire resistant pattress for it, but totally pointless IMO as if that has been exposed to fire and has 'gone up in flames', you have much bigger problems to worry about at that point I assure you  

One thing we always do is fit a multi-sensor smoke detector in every single plant space, as early warning is what will pay dividends here, not what the 300mm around the CU is made from !! By the time fire / flames have got to that, the fire would be quite involved and the smoke detection system should have alerted the occupants WAY before the worry of how long the plywood will burn for is a question. Fire goes upwards as well as backwards, but upwards a HELL of a lot quicker...