3rd Amendment Metal Consumer Units - best practice advice please

[The General]

Afternoon all,

I've been doing domestic electrics for about 4yrs now and although I've done a few circuit alterations on metal clad consumer units I'd say that 95% of my work has been with plastic ones. I'm totally comfortable with replacing a consumer unit and all that it entails, but I've not done any commercial or industrial work - so I've had very little exposure to the actual 'physical experience' of working with metal boxes.

I'm hoping that those more experienced than me may be able to offer some help/advice on working with a metal clad box.

For instance, are there any handy little tools which I'm going to need to buy which will make life easier?
Are there any pearls of wisdom you can offer which might save me from a lot of cursing and swearing!??

I know that often, experience can only be gained by actually doing it, but I'm hoping that I might be able to learn from good examples before I end up making too many mistakes.

Thanks in advance for your input,

 

[Midwest]

To or from who?

I emailed Elecsa Tech Support in July;

'Dear Tech Support,

With regard to reg 412.1.201, I have been reading quite a few threads on forums on this reg, suggesting certain installation procedures...................

2. Cable entries should be sealed with intumescent materials to prevent the spread of fire.

I cannot see that mentioned in 412.1.201, although I have seen an pdf file from IET, suggesting it should.'

Reply back;

..........Cable entries should be kept to a minimum and there should be as little spare room around the cables and the grommets etc as possible. There’s no specific requirement to seal the holes around cables when they enter the CU, unless there’s a specific statement from the manufacturer of the CU stating to do so.

So, I think I will see further guidance from them by email.

 

[Octopus]

I emailed Elecsa Tech Support in July;

'Dear Tech Support,

With regard to reg 412.1.201, I have been reading quite a few threads on forums on this reg, suggesting certain installation procedures...................

2. Cable entries should be sealed with intumescent materials to prevent the spread of fire.

I cannot see that mentioned in 412.1.201, although I have seen an pdf file from IET, suggesting it should.'

Reply back;

..........Cable entries should be kept to a minimum and there should be as little spare room around the cables and the grommets etc as possible. There’s no specific requirement to seal the holes around cables when they enter the CU, unless there’s a specific statement from the manufacturer of the CU stating to do so.

So, I think I will see further guidance from them by email.

Wow... that's almost in plain English!

 

[Midwest]

Mr Cable & Mr Staniforth, also discussed 421.1.201, in the Certsure 'webinair'. No mention of fire containment, and described the move from plastic to metal, to remove the fuel source (plastic CU) from any fire.

 

[Octopus]

Mr Cable & Mr Staniforth, also discussed 421.1.201, in the Certsure 'webinair'. No mention of fire containment, and described the move from plastic to metal, to remove the fuel source (plastic CU) from any fire.

@ Elex, Sandown Park in 2014 stated that all these special cables entries were required!

AND he didn't like it when I asked why the schemes hadn't suggested a mains powered smoke in the same room as a sensible alternative!

 

[Deleted member 9648]

I'd agree with all of the above posts on what a nonsense the whole situation is. Regarding sealing of cable entries it has been rightly stated that Bs 7671 does not make specific reference to that,only the guidance note. Personally I do not believe that lower and rear cable entries are too much to worry about. I had this discussion with our NICEIC man and we were in agreement that avoidance of top entry or high level side entries are sufficient for adequate fire containment.

 

[Midwest]

Having read that page from GN4, it does not actually say that cable entries should be sealed with intumescent material, merely that they are sealed, and good workmanship & proper materials used, or am I missing something again?

 

[Midwest]

I'd agree with all of the above posts on what a nonsense the whole situation is. Regarding sealing of cable entries it has been rightly stated that Bs 7671 does not make specific reference to that,only the guidance note. Personally I do not believe that lower and rear cable entries are too much to worry about. I had this discussion with our NICEIC man and we were in agreement that avoidance of top entry or high level side entries are sufficient for adequate fire containment.

Only problem with that wirepuller, is on a replacement CU, on some occasions if you don't use the top, you might have to joint or extend the existing cables. What enclosure do you use for that?

 

[Octopus]

Only problem with that wirepuller, is on a replacement CU, on some occasions if you don't use the top, you might have to joint or extend the existing cables. What enclosure do you use for that?

which is the point I tried to make in post #20

 

[shanky887614]

i think im going to put myself on the 2394/5 combined course at the start of next year. there is a place near me that does it for 760 ex vat for both

 

[UNG]

Cheers Murdoch.
To my mind it's an ill thought out and poorly implemented regulation. I don't have anything against fitting metal boards as such, especially now the prices have stabilised. But it was designed to combat fires resulting from poor installation and dodgy components, neither of which I feel apply to a fully qualified and experienced electrician as myself. If the intention was other than is stated then more fool the IET for not being able to agree on the wording of a paragraph to fulfil a clear intention.

Sums up my thinking as well

This reg is a poor excuse to address a problem without addressing the actual cause and all the stats used to support it's introduction are based on an area of just over 600 sq miles when the UK has area of around 94,000 sq miles in total it seems that the London Fire Brigade has a lot more clout over the rest of the UK than it really needs.
From the national annual fire figures I have looked at for the last 8 - 10 years the increasing level of consumer unit fires seems only to be an London issue although none of the stats including London have no in depth analysis of "electrical fires" to verify this fact.
May be an analysis of qualification and competence by area would have been a good parallel to look at in conjunction with the fire stats
There seems to have been a lot more effort and hysteria put into ridding the UK of plastic consumer units than that of the provision of fire resistant cable supports on exit routes which I consider to be a much more critically important safety issue

I'm surprised that they have not asked for a smoke / heat detector to be located adjacent to a CU to make sure there is an early warning of a fire

My pet hate at the moment is all the hype and misinformation out there relating to the use of plastic consumer units and the probable knock on effect from the scammers selling people something they do not really need

No doubt in a few years time when the merry go round has gone full circle we will be told that metal consumer units are dangerous because they are badly installed

In the 30+ years I have been in this trade I have seen only 2 or 3 consumer units that have been close to causing a fire and fitted more than I care to remember with no problems that I know of

What effect will sealing cable entries with mastic of any sort have on the cable insulation in the long term is an unknown factor that does not appear to have been considered in all of this guidance

 

[Deleted member 9648]

Only problem with that wirepuller, is on a replacement CU, on some occasions if you don't use the top, you might have to joint or extend the existing cables. What enclosure do you use for that?

Any enclosure you like. It is the DB and associated switch gear that the requirements apply to.

 

[shanky887614]

Any enclosure you like. It is the DB and associated switch gear that the requirements apply to.

not the dno kit though and i bet that was what is causing a lot of fires in london, afterall its that overloaded and it should have been improved/replaced decades ago

 

[stevethesparks]

intumescent grommets - do they exist?

 

[davesparks]

intumescent grommets - do they exist?

Not yet, but I'm sure they'll be along soon

 

[Midwest]

Any enclosure you like. It is the DB and associated switch gear that the requirements apply to.

Yep I thought that, but having asked Elecsa Tech Support twice now, and was told they considered that an enclosure designed specifically for housing joints to extend existing cable for CU replacement (like the Wago DRE-5) would be regarded a 'associated switchgear'. Mr Connexbox didn't like that, when I told them. And Mr Staniforth didn't agree, on their 'webinair' video. I get the feeling, that nobody really knows what is what with this reg.