Junction Box for Extending Old Wired Fuse Board

[Vitesse]

I went to look at a job the other day for a customer to install a Hot Tub supply in the garden. Whilst there I found that an 'electrician' in the past had extended all the cables down from where an old wired fuse board used to be located to an RCD protected CU.

It was basically a bodge where they had crimped and terminal blocked all the existing T&E, to new and tried to ram it all inside a JB to make it look pretty but over time the JB had split in two and when I took the cover off I found an unsafe mess with obvious signs of damage between conductors that looked like someone had decided that a bit of insulating tape would resolve the problem!

I said to the customer the first priority before I do anything is to sort out that mess, which he has no problem with. I also pointed out that I would need to test each circuit to make sure they were all ok.

You can see the brickwork where the old fuse board used to be. Above the white is plasterboard that goes up about a foot before it disappears into the floor void above and all the T&E is run in galvanised steel attached to the brickwork. I can remove that plasterboard and free up some slack to allow me to terminate it okay.

My question is I am looking at terminating in a JB using din rail mounted Legrand Viking 3 terminal blocks, I can't remember the exact number of circuits it's written down in my note book in the van but I think it was 3 x 2.5, 2 x 1.5 and 1 x 6. If I go down this route does the JB need to be metal to conform with AMD3? It's probably in the grey area!!!!

Or does anyone have any better suggestions to extend the circuits down safely?

 

[Richard Burns]

I am pretty sure that a junction box, even with DIN rail terminals would not be classed as a consumer unit compliant with BSEN61439-3.

Just make sure the cables are correctly and securely terminated and it should be fine.
And considerably better than the pictured mess!

 

[Wilko]

Hi V, thanks for the pic. Makes me feel positively clever. I would love to see the 'after' if you've got time. Cheers, David.

 

[Pete999]

I am pretty sure that a junction box, even with DIN rail terminals would not be classed as a consumer unit compliant with BSEN61439-3.

Just make sure the cables are correctly and securely terminated and it should be fine.
And considerably better than the pictured mess!

If what you say is the case, and I;m not doubting you, it makes a mockery of the excuse for using non combustible enclosures for CUs, because they will probably be very close, almost like saying it doesn't matter about the JBs connections being loose, but it does in the CU, where is the logic for that then? oh sorry it's the IET that set Amd 3 logic and the IET don;t go well together do they?

 

[ackbarthestar]

As long as the remedial work leaves the finished item safer or not less safe than the original art work then it conforms with the regs. Whether it should comply with AMD3 is another matter as there is no switchgear, protective devices, control gear. However, there will be terminations and we know that it is loose terminations that cause the majority of fires.

 

[Risteard]

Whether it should comply with AMD3 is another matter as there is no switchgear, protective devices, control gear.

It absolutely MUST comply with Amendment No. 3 as these are the Regulations in force for all work now - 421.1.201 is in no way relevant to a junction box though!

 

[Pete999]

As long as the remedial work leaves the finished item safer or not less safe than the original art work then it conforms with the regs. Whether it should comply with AMD3 is another matter as there is no switchgear, protective devices, control gear. However, there will be terminations and we know that it is loose terminations that cause the majority of fires.

So the way you see it is as follows: two enclosures, one with connections only, the other the CU has connections and switches etc, situated more than likely very close to each other, probably joined by some mechanical connections, say bushes and lock nuts, one being made of a combustible material the other non combustible, confused dot com, no logic there is there? Not doubting you just thinking things through.

 

[westward10]

Good question about whether it should be metal or not cos it ain't a CU or a similar switchgear assembly (quote from regs). I am with Pete on this, take away the components of the CU and suddenly it doesn't matter?
I would use a metal enclosure, no comebacks then.

 

[Risteard]

I would use a metal enclosure, no comebacks then.

As I say there is no possible argument as to how 421.1.201 could apply - a junction box can in no way be construed to be a similar switchgear assembly to a type-tested distribution board - indeed it isn't even a switchgear assembly!

But you are certainly welcome to use a steel box if you want. However in no way could it be argued that there is any requirement if plastic was suitable for the environment etc.

 

[Midwest]

I asked Elecsa technical way back when if I could use the New DRE-5 v2 DIN Rail Enclosure - https://www.connexbox.com/dre-5-din-rail-enclosure.html for a CU move, and was told 'no, it has to be A3 non combustible', only to watch an NICEIC/Elecsa 'Web in Air', where Darren Staniforth said such plastic enclosure could be used. I sent another email to Elecsa Tech Support, to ask if they could clarify such a discrepancy in their advice they are giving. Tumble weed, no reply.
Think the issue is, 421.1.201 is so vague, and the 'grown ups' haven't really got their collective heads around this. I spoke to a Connexbox rep, who was not a happy bunny. He said he was going to raise the subject with IET etc. I notice their gallery on the enclosure with a CU change is no longer on their site?

 

[westward10]

As I say there is no possible argument as to how 421.1.201 could apply - a junction box can in no way be construed to be a similar switchgear assembly to a type-tested distribution board - indeed it isn't even a switchgear assembly!

But you are certainly welcome to use a steel box if you want. However in no way could it be argued that there is any requirement if plastic was suitable for the environment etc.

Am agreeing with you totally, but a box full of DIN rail connectors poses just as much of a risk.

 

[Vitesse]

Ooh that enclosure looks perfect. Thanks for posting that. The wording of 421.1.201 clearly says Consumer Units and similar switchgear, as there is no switchgear in what I am doing, then I will interpret it that a plastic enclosure is ok. As others have said, anything to tidy up that mess has got to be safer.

The CU itself is probably about 2 meters away in another cupboard, so the joint box enclosure is not going to get damaged if the CU decides to self combust, unless the whole house burns down!!!!!!

 

[Risteard]

a box full of DIN rail connectors poses just as much of a risk.

Oh, I completely understand that point. And as I said you are free to use a steel adaptable box to mitigate any danger. But I would avoid trying to tie yourself to Regulations which don't exist.

Just accept that BS7671 is a minimum standard which you are welcome to exceed.

 

[Midwest]

As I say there is no possible argument as to how 421.1.201 could apply - a junction box can in no way be construed to be a similar switchgear assembly to a type-tested distribution board - indeed it isn't even a switchgear assembly!
.

Clearly you have done some research on this subject, I do remember some edict from somewhere on a clarification of 'similar switch gear assemblies', as BS7671 only defines 'Switchgear'. Can you provide a link or reg update?

 

[Lucien Nunes]

AMD 3 is always a popular subject for IET-bashing, but it might have been one of the few options that stood a chance of controlling the spate of CU fires that was actually within their scope. They aren't reponsible for policing ports for defective imported goods made of too-flammable plastic, so they can't directly control what tat gets installed. They can't throw people in jail for installing it wrongly. But they still have to somehow reduce the incidence of fires. Bad connections have been overheating since the beginning of electrical wiring, often due to poor work. But they can't ban connections, nor realistically insist that every connection is enclosed in a non-combustible casing (all-metal PIR casing?). What they have to do is pinpoint the hotspots (literally) and do something to contain them.

In a CU there are many connections and potential heat sources, contacts that can arc and indeed probably will at some point, all lumped together in one place. In a domestic situation, other than the shower or cooker circuit by far the largest currents flow there, plus the highest PFCs are found there. The connections in the CU are the ones most likely to be disturbed again and again during EICRs. Compared to many other accessories, the CU is likely to be hidden from view. With all these fire risk factors located in one place, a logical man might say, if there was one electrical assembly in a house, other than current-using equipment, that was most likely to benefit from a non-combustible enclosure, on balance of probabilities it would be the CU.

OK you can contrive a situation where there is as much risk of terminal burnout in a multi-circuit junction box (although there still won't be any terminals carrying the total installation load like in the CU) but that is the exception rather than the rule. And if the terminals are say Wagos or other semi-foolproof types or well-engineered DIN rail terminals, actually they are less likely to make bad connections than the CU busbar.
So while AMD3 metal CUs are a workaround that fail to solve the the core problem, I personally don't think they are as bad an idea as some people make out, nor that it is illogical to require a metal CU, but allow a nearby multi-circuit JB to be plastic.