Junction Box for Extending Old Wired Fuse Board

[Vitesse]

In my experience I have been to people's houses and I don't know if I have particularly good hearing but you can quite often hear the arcing in the CU. The reason I say that is I went to a house recently and another spark had been there before me and couldn't fix the problem. As soon as I took the cover off I could hear the buzzing straightaway, how the last guy had missed it I don't know?

It turns out someone hadn't terminated at least 2 of the MCB's cage clamps on the busbar properly and it had virtually eaten away the cooper prongs on the busbar.

 

[Risteard]

A junction box used in this scenario IS a distribution board, is it not? it's distributing circuits to the CU.

That isn't the definition of a distribution board given in Part 2 of BS7671 though, or indeed a consumer unit which is described as a type-tested distribution board etc.

Unfortunately I don't have my copy of BS7671 on me at the minute to list the precise Definitions.

 

[Pete999]

That isn't the definition of a distribution board given in Part 2 of BS7671 though, or indeed a consumer unit which is described as a type-tested distribution board etc.

Unfortunately I don't have my copy of BS7671 on me at the minute to list the precise Definitions.

It's an anomaly that the mandarins at the IET seemed to have missed imo, it's clear to me that bad connections, which after all is what we are concerned with can happen in theses JB just as easily as in a CU

 

[Risteard]

it's clear to me that bad connections ... can happen in theses JB just as easily as in a CU

Of course that is true. Indeed how often do we come across burnt-out neutral connections in a shower pullcord?

 

[Richard Burns]

Since I am a definite nay sayer about the non combustible enclosure issue and do not have the confidence that it is at all a good idea my views are somewhat skewed.
One can see what the IET have attempted (and in my opinion failed) to address and it is possible that in maybe one or two cases it may help.

However bringing in the argument that any junction in a cable is liable to overheat starts you on the path to eliminating plastic entirely as an enclosure material in any installation and this I believe would raise much greater risks of shock than the fairly low risk of fire (not overheating).

It is clear that the congregation of connections in close proximity can increase the risk, as evidenced by the OP's picture of the short in the JB, but without the designed heating of parts in MCBs and the switching arcs of tripping the risks are reduced. And in my opinion the risks were not high enough to address in the first place.

 

[Midwest]

If I was an apprentice coming into the industry in a few years time, I would come across reg 421.1.201 and would probably be told of some of the background of its instigation or conception, but I would naturally just accept it as it is, just as I would with the many other regulations.

But without the specialist knowledge and expertise that others have, I would be surprised that I could replace an A3 consumer unit with a plastic enclosure with din rail terminal connections to extend the final circuits, so that I could lower or relocate another replacement A3 (or A4 or whatever) consumer unit. The logic of that would be beyond me. But then I would be just a lowly apprentice, and would tip my hat to their astuteness.

 

[crossplot]

View attachment 33359 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?

Well, sorry bud, but had I seen something in such poor condition, the least I would be advising is a rewire(If there is not sufficient slack to terminate into a new fuseboard) of the first and last legs of the ring main and lighting/ or affected circuits.
Im not doubting you will leave it in safe condition, but you are last man in.

Are you really going to be happy leaving a termination box metal or other in situ after you have seen it? I wouldn't!

Just my 2p's

 

[Andy78]

Well, sorry bud, but had I seen something in such poor condition, the least I would be advising is a rewire(If there is not sufficient slack to terminate into a new fuseboard) of the first and last legs of the ring main and lighting/ or affected circuits.
Im not doubting you will leave it in safe condition, but you are last man in.

Are you really going to be happy leaving a termination box metal or other in situ after you have seen it? I wouldn't!

Just my 2p's

What aspects of and issues with a connection box to extend cables would you not be happy with to necessitate hundreds of pounds worth of disruptive work ?

 

[westward10]

Well, sorry bud, but had I seen something in such poor condition, the least I would be advising is a rewire(If there is not sufficient slack to terminate into a new fuseboard) of the first and last legs of the ring main and lighting/ or affected circuits.
Im not doubting you will leave it in safe condition, but you are last man in.

Are you really going to be happy leaving a termination box metal or other in situ after you have seen it? I wouldn't!

Just my 2p's

Can't see how you can justify a rewire from viewing a single picture?

 

[Vitesse]

Well, sorry bud, but had I seen something in such poor condition, the least I would be advising is a rewire(If there is not sufficient slack to terminate into a new fuseboard) of the first and last legs of the ring main and lighting/ or affected circuits.
Im not doubting you will leave it in safe condition, but you are last man in.

Are you really going to be happy leaving a termination box metal or other in situ after you have seen it? I wouldn't!

Just my 2p's

Well as I said in the original post. I can free up slack by removing some plasterboard. The house was probably built in the 1980's and the internal wiring is in very good condition. The only problem with it is where some cowboy has come along and put that JB in and crammed everything inside it.

If it is terminated correctly in a suitable enclosure that contains correctly rated terminals then I am more than happy to do so. Why do manufacturers make such enclosures and terminals if you deem them unsafe? I am sure they do plenty of R&D to ensure what they sell is safe. If you took your train of thought then nobody would use Wago's or similar.

 

[sparksburnout]

Well, sorry bud, but had I seen something in such poor condition, the least I would be advising is a rewire(If there is not sufficient slack to terminate into a new fuseboard) of the first and last legs of the ring main and lighting/ or affected circuits.
Im not doubting you will leave it in safe condition, but you are last man in.

Are you really going to be happy leaving a termination box metal or other in situ after you have seen it? I wouldn't!

Just my 2p's

The least is a rewire?? Whats the best option then??? "Oh sorry love, thats £££££££££££'s that job"...............What a load of nonsense.

 

[Vitesse]

The bits arrived today to complete the job. The Wiska Topline connectors are a quality bit of kit. First time I have used them so I wasn't sure what size enclosure I would need, so I ordered din rail connectors first so that I could get the measurements correct. I had a chat with the guy at Connexbox and he is really knowledgable and knows his stuff, I got the impression he is an ex Spark?

 

[Wilko]

View attachment 33451 ... I had a chat with the guy at Connexbox and he is really knowledgable and knows his stuff, I got the impression he is an ex Spark?

Hi - Ray from there was a golden source of info for me on MF, maybe same guy? Cheers, David.

 

[Vitesse]

Hi - Ray from there was a golden source of info for me on MF, maybe same guy? Cheers, David.

Possibly he was very chatty and we had the discussion about AMD 3 and the requirements for IP4X on these enclosures. I did ask his name but he had to rush off and sort the post out and forgot to tell me.