All very true.
Many people would probably share your preference although, in reality, I don't think it really makes appreciable difference - there's not even much difference in terms of 'the number of conductors inserted into terminals'.
Kind Regards, John
The only actual benefit is one less in-line join over the middle option and not having to find a place for it.
I don't think that differs all that much from my "no appreciable difference" view
Kind Regards, John
No it doesn't apart from being a tiny bit tidier.I don't think that differs all that much from my "no appreciable difference" view
Kind Regards, John
A final circuit is one that supplies socket outlets or current using equipment directly, a distribution circuit is one that runs from one distribution board to another.
"Ring final circuit" is the proper term for what most DIYers (and probablly many domestic sparkies too) call a ring main.
Neither part P, nor the associated notification requirements get into such minutae.
Terminating conductors in this context refers to connecting them to terminals.
This needs to be done in a safe and appropriate manner. Unlike some countries we don't require manufacturers instructions to be followed to the letter, but still they should be taken into consideration. As you increase the number of conductors in a terminal hole or mix different types and sizes of conductor in the same terminal hole, you increase the risk that one or more of those conductors will not be clamped adequately. The design of the terminal also plays a role pf course, oldschool junction boxes only have on terminal hole (well strictly slot) per pole forcing you to have multiple wires in the same terminal . At the other extreme the push-in and lever terminals that are becoming increasingly common are generally only suitable for one wire per terminal hole.
Exactly how many wires is too many for a traditional tunnel-style screw terminal is probably not something everyone will agree on, but I would say 3 is ok, 4 is pushing it and more than 4 is probably a bad idea. I don't think I have ever seen a manufacturer advertise a single terminal hole as having capacity for more than 3 conductors. I find this particularly strange with the oldschool junction boxes as they have four cable entries, yet the datasheet I found for one only specified 3 conductors per terminal.......
If you want to take three spurs from the same junction box, I would suggest the Wagobox 221-4 with Wago 221-415 series terminals.
For more than 3 spurs you could use the Wagobox XL or XLA with appropriate terminals.
I would imagine that most people would agree with that, particularly for the terminals in "13A" BS1363 sockets, but ...
Again, in terms of "13A" BS1363 socket terminals (and probably many other accessories), that is probably true. However, in terms of "terminal holes" in general, the following are a few snippets from an MK catalogue ....
BS546 sockets____ 3-pole Fan Isolators.________ Cooker Control Units etc._________ "Plate Switches (in general)
Grid Switch Modules ________ ... and of particular interest MK1131 (10A,4 term) & MK1132 (30A, 3 term) JBs
... so, in terms of the general, some manufacturer *well, at last MK) do "advertise a single terminal hole as having capacity for more than 3 conductors
The most common type have a rotatable cover which enableone to choose which, and how many, of the cable entries one want to be 'open' - so maybe the idea is that it enables you chose which 3 (or less) you wish to use?
I agree with all that.
Kind Regards, John
Fair enough.
Though the 2A socket seems the only one where a single terminal hole is advertised as taking more than 4 conductors. I do wonder if that is a mistake that didn't get caught/didn't get sufficient engineering review.
The MK junction boxes have multiple terminal holes per pole rather than the traditional single slot with a screw entering from the top. I presume the figures given refer to the pole as a whole and not the individual holes.
Hager's 30A 3 terminal traditional junction box does seem to be rated for 4x2.5, though strangely their 4 terminal lighting junction boxes only seem to be rated for 3 conductors per terminal which leaves an open question about earthing...........
It is, but I was responding to your comment that you hadn't seen MIs specify "more than 3 conductors) -and there seem to be a good few 4s out there.
I agree, and probably should have mentioned that I strongly suspected that it was a typo, and probably should have been 4 (i.e. the same as for 1.5mm²) - which is why I did not 'highlight' the apparent "7"! However, that is again still greater than 3
Good point - I'd totally forgotten that. Having now been reminded, it seems that they are specifying 2 x 1.5 mm² 'per hole' for the 4-pole ones and 1 x 4mm² 'per hole' for the 3-pole ones, which is fair enough.
I suppose there are some swings and roundabouts in relation to MK's way of doing it, since it means that N conductors per pole has N (rather than just one) screwed connections per pole, and with no direct conductor-to-conductor contact.
I'm not sure I understand your point. With a 4-terminal 'lighting JB', one will usually use three of them for L, S/L & N, and then the fourth one for earth/CPC, won't one?
Kind Regards, John
Yes, which means you normally will have three wires in permanent live, three wires in neutral, 2 wires in switched live and four wires in earth.
So a lighting junction box which is only rated for 3 wires per pole seems to fail at it's primary purpose, which says something about either the people who designed the product or the people who wrote it's documentation.
Ah, good counting
You didn't mention the conductor size, but if it's rated for 3 x 1.5mm² conductors, then 4 x 1.0 mm² CPCs shouldn't be a problem - so, although I agree that that the writing of the documentation is non-ideal, electrically it should be fine.
As for "the people who wrote the documentation", you may recall that a good few years back I had conversations with a couple of MK technical guys (who seemed sensible and fairly clued up), in attempts to get to get to the bottom of the oft-debated question of the 'current rating' of MK double socket. The "Technical Data Sheet" says (generically, in relation to single, double and triple sockets) "13A per socket outlet, except for triples when it is 13A total", so the crucial question is what it means by a "socket outlet". Both guys offered their oen opinions, but said that they couldn't answer for the intent of the content of the ("Technical") Data sheet, because such documents were written by the Marketing Department, not the Technical Department
Kind REgards, John
@jocollett after all of that advice, can you advise on what you plan to do.
one important thing that has not been mentioned. If you use junction boxes with screw terminals, then these must be accessible. If the junction is not accessible then they must be products that are classed as “maintenance free”.
There are ready made products that are MF such as THESE
also custom solutions such as the WAGO connectors and boxes.
The type of JB is going to limit the number of connections at any point.
one important thing that has not been mentioned. If you use junction boxes with screw terminals, then these must be accessible. If the junction is not accessible then they must be products that are classed as “maintenance free”.
There are ready made products that are MF such as THESE
also custom solutions such as the WAGO connectors and boxes.
The type of JB is going to limit the number of connections at any point.
I would not even try to get four 2.5mm into one 30amp JB terminal, the grub screw would struggle to even catch the tread.
One solution, and good practice - is to fit the ring cable into the terminals without actually cutting the ring cable. Strip it perfectly to just neatly fit in the terminals and pass straight through the JB. Two more 2.5mm cables can then be easily fitted in the terminals. Earth sleeving cannot then be fitted on the earth wires, but a small concession to make, for a tidier and safer outcome.
Back in the past that might have been "good practise".
But junction boxes (that could have been used as you describe) had screw terminals.
Most ring final cables live under floors or are buried in walls which means that type of JB cannot be used today, as they are unaccessible.
That is though, the style of JB under general discussion. The location of the JB's has yet to be discussed.