?? why?

[SUNRAY]

I have known very many properties that have had countless 'brown JBs' under the floorboards, and can't recall having personally ever been aware of any of them resulting in any problems - so I do have to wonder how common the perceived 'problem' actually is. Indeed, even if they are not particularly 'well made' or particularly 'substantial', I'm not sure that they would be likely to result in problems when left undisturbed under floorboards for a few decades!

Other than bad workmanship the problem is copper creep which is aggravated by heating and cooling cycles. Like you I've not knowingly encountered a properly installed JB failure. Sure I have where it is apparent that it was not properly installed and on a regular enough basis to wonder if it was an issue with the JB or the concept.

Two of the bugbears I have:
The lack of thread length making the terminal tricky to load without the screw falling out which could result in a poorly completed termination as multiple wires and fiddly screw are wrestled into position,
Another being the ease of crossthreading the screw which commonly spreads the terminal slot open, causing a poor joint and cracking the Bakelite (sp?) -
I'd put those down to bad installation with an element of less than ideal design.

 

[JohnW2]

Other than bad workmanship the problem is copper creep which is aggravated by heating and cooling cycles.

Yes, I realise that is the theoretical issue, but ...

Like you I've not knowingly encountered a properly installed JB failure.

... so, again, I have to wonder how often that theory is actually realised in practice.

 

[Harry Bloomfield]

One of the bugbears I have is the lack of thread length making the terminal tricky to load without the screw falling out which could result in a poorly completed termination as multiple wires and fiddly screw are wrestled into position, another being the ease of crossthreading the screw which commonly spreads the terminal, causing a poor joint and cracking the Bakelite (sp?) - I'd put those down to bad installation.

Yes, yes, and yes. They are rather poorly designed, a proper screw terminal would be more sensible, but the point of the threaded brass U, it forces you to ensure that the conductors, entering from each side, have to overlap, lowering the resistance of the termination. You can do that with the traditional two screw 'choc block' terminals, but it doesn't force you to do it - I have seen a number, of over-heated versions of the latter, so I make a point of always over-lapping the conductors, in those.

 

[SUNRAY]

Yes, yes, and yes. They are rather poorly designed, a proper screw terminal would be more sensible, but the point of the threaded brass U, it forces you to ensure that the conductors, entering from each side, have to overlap, lowering the resistance of the termination. You can do that with the traditional two screw 'choc block' terminals, but it doesn't force you to do it - I have seen a number, of over-heated versions of the latter, so I make a point of always over-lapping the conductors, in those.

Although I agree and regularly do the same, I have had work snagged for doing so. I really can't see a downside to doing it.

 

[Harry Bloomfield]

I really can't see a downside to doing it.

The only downside, is if the ends of the conductor are too long, and poke out the far end.

 

[SUNRAY]

The only downside, is if the ends of the conductor are too long, and poke out the far end.

Yes but that counts as bad workmanship.

 

[Harry Bloomfield]

Yes but that counts as bad workmanship.

In my book too.

 

[ebee]

I'd put those down to bad installation with an element of less than ideal design

Yup I agree with those observations especially so with the cheaper types too. I am not an absolute fan of junction boxes anyway but some in particular, I have however found a very few to be quite reasonable and being of tunnel terminal design rather than split grubscrew.
I always look upon a JB to be an afterthought addition rather than proper planning by design so best avoided if possible.
Another concept if using the grubscrew type is example for a spur from the ring final is to keep the original ring conductor wholesome and purely remove enough of the sheath and insulation into the split once grubscrew is removed then to add the spur conductor once the grubscrew is already in the thread before fully screwing home, leaves the ring conductor intact and any point of failure is limited to the spur conductor which hopefully minimised by current transfer and time period of that transfer. Makes it possibly a bit more resilient. You can also achieve a similar idea with the tunnel terminal type if you are able to double the conductor. Of course it means if you have sufficient existing slack and it requires a bit more care therefore time to do it.

Does not the whole concept of the requirement for ''maintenance free' JBs relate only to inaccessible joints in the conductors of cables - and hence not to situations in which the conductors of a single cable are simply terminated ('parked') in the terminals of some sort (any sort) of JB?

I will have to re-read part of this thread to understand the context tomorrow John

 

[JohnW2]

I will have to re-read part of this thread to understand the context tomorrow John

The thread has jumped about a bit, but my understanding is that most of it (including your post to which I responded), other than the earliest bits on page 1, stemmed from, and related to ...

.... I smacked the tiles off the wall where the shower was and there was a double socket box with live cables terminated in a junction box buried underneath the tiles ... In the days when the room was just a bedroom, they didn't bother to get rid of the socket wiring when they put the shower in!

(a situation which Sunray suggested deserves a "C1" !). If that's the case, then we are merely talking about an (albeit 'live') cable terminated/parked in a buried JB behind tiles. As I've said, if there was no 'connection' to anything else, then I don't believe there would be a requirement for 'MF' - and hence I cannot convince myself that the situation would deserve any coding on an EICR, let alone Sunray's C1

Kind Regards, John

 

[securespark]

There were two ring final legs, if that makes a difference.

 

[securespark]

I am more concerned with -

Why?

 

[ebee]

The thread has jumped about a bit, but my understanding is that most of it (including your post to which I responded), other than the earliest bits on page 1, stemmed from, and related to ...

(a situation which Sunray suggested deserves a "C1" !). If that's the case, then we are merely talking about an (albeit 'live') cable terminated/parked in a buried JB behind tiles. As I've said, if there was no 'connection' to anything else, then I don't believe there would be a requirement for 'MF' - and hence I cannot convince myself that the situation would deserve any coding on an EICR, let alone Sunray's C1

Kind Regards, John

Ive not read thru it adequately yet John but here goes. My concern would be yes if current running thru the joint such as in a ring or radial being one possible concern . the other concern is mains voltage present capable of tracking back via moisture in the wall tiles etc and giving you a nip. there is not only electrocution to consider but electric shock causing an involuntary action which could cause a fall, slash your wrists etc etc, being startled in itself and your sudden instinctive reaction to it can be a source of possible danger. One typical example might be you up a ladder at the top of your stairs and you working on a live ceiling rose. You are clumsy and get a quick nip. No Electrocution, Not Even a big sudden shock, but a nip sufficient to cause you to suddenly move in such a way that causes imbalance and you fall not only off the ladder but tumble downstairs and break your neck. You are still dead even though you have not actually been electrocuted but it might be considered as "death (or injury) by electrics". Avoid electric nips, especially sudden unexpected ones!

 

[JohnW2]

There were two ring final legs, if that makes a difference.

If the two legs were (electrically) 'joined' in the box behind the tiles then, yes, that would totally move the goalposts - since, at the least, it would then be required that those joints were 'MF'.

 

[JohnW2]

Ive not read thru it adequately yet John but here goes. My concern would be yes if current running thru the joint such as in a ring or radial being one possible concern .

My comment was solely in response to your mention of MF joints and that is only relevant when there are 'joints' (through which current flows, or may/could flow).
However, contrary to what I was previously thinking, secure seems to now be saying that there was a joint between two cables - in which case, at the least, the joint would have to be MF.

.... the other concern is mains voltage present capable of tracking back via moisture in the wall tiles etc and giving you a nip. there is not only electrocution to consider but electric shock causing an involuntary action which could cause a fall, slash your wrists etc etc,...

Are you related to bernard? The same can be said (as bernard often does say), of any electrical accessory mounted on a potentially damp wall. One can't deny the theoretical possibility you mention but the chances of it ever doing appreciable harm in practice must surely be vanishingly small - even more so behind glazed tiles than in one of bernard's damp walls.

In any event, as I said, my comments were about the requirement (or not) for 'MF' terminations/joints - and MF JBs are not required to offer (and do not offer) any protection against water or moisture!

Kind Regards, John

 

[securespark]

It seems a few people have missed the fact that I mentioned in a couple of places that there was more than one cable.

EFLI, not sure why you asked, initially it was an electric shower, then replaced with a thermostatic mixer valve.