Steel container below the fusebox?

[plugwash]

Looking at clives teardown video it seems the wago 221s are using steel springs to push the wires against tinned copper busbars.

 

[JohnW2]

Looking at clives teardown video it seems the wago 221s are using steel springs to push the wires against tinned copper busbars.

That would certainly make sense, but the potential issues of 'contact area and contact pressure would presumable still exist.

 

[ebee]

I must say whether springs or terminals then the flat against curve (diameter) idea does concern me a bit. That is why I prefer round shaft in a roud hole sort of idea - tunnel terminals filled (as near as possible filled) by a round conductor, plenty of diameter to make contact - ideally the whole diameter but in reality, much of it at best, as opposed to cage clamps and the like. if the wago spring was curved to make a nearer fit to its intended conductor size I would feel a little happier about likely contact area. Is it so curved?

Of course whether a lot of the curved bit or a single point we might have a largish length of contact so that point becomes a line etc so that would help too

 

[JohnW2]

I must say whether springs or terminals then the flat against curve (diameter) idea does concern me a bit. That is why I prefer round shaft in a roud hole sort of idea - tunnel terminals filled (as near as possible filled) by a round conductor, plenty of diameter to make contact - ideally the whole diameter but in reality, much of it at best .....

I can't really disagree with any of that. However, two or more round conductors in one large round hole is clear not quite as 'comforting at that.

In practice, given that copper is pretty soft and that we do unscrewed terminals pretty tight, I imagine that the geometry of the situation (and contact area) gets better when we tighten screw terminals.

I doubt that the springs of spring-loaded terminals are strong enough to produce much deformity of the conductor - but, of course, few (if any) such terminals are designed/intended to take more than one conductor.

 

[ebee]

However, two or more round conductors in one large round hole is clear not quite as 'comforting at that.

Hmmm.
OK then.

Firstly, with say two solid conductors in say 1.0/1.5/2.5 bog standard T & E - then (two dimensionally speaking) each conductor has one point of contact on the circumference of the terminal circle, one point of contact on the screw point (slight dome preferred), and one point of to each other.

If such terminals has two screws in the terminal then so much the better.
Doubled the points of contacts and giving a better mechanical anchor too.

If we double over each conductor we are up to doubling the points of contact (my preference - I dislike twisting of solid conductors).
Secondly - say seven strands of some other common T & E sizes then we now have more points of contact, albeit some smaller touch areas.
If we twist, slightly, each conductor and then double over each conductor then more points of contact in a similar fashion - I dislike twisting two or more t stranded together as one for similar reasons to the singles.

In an ideal world, that does not exist, the aim would be to fill the terminal with conductor.

With sockets of say one conductor to each terminal I would usually double twice each therefore quadruple for the same reasons of touch.
On a ring final with a spur I have three conductors per terminal and I used to double those and they still went into the terminal without too much extra effort and was very near to my idea of filling the terminal therefore more area of contact.

Indeed, in more recent years, the terminal holes became slightly tighter therefore the spur I might use only singly - this also aids identification as to which two conductors are the ring proper and which conductor is the spur. Obviously a radial with a spur of say 3 x 2.5 conductors in a similar fashion, you might have a spur or branches of treelike.

Years ago a bloke told me that he and a pal "rewired a house (occupied) in a weekend, Hmm I thought "That sounds fast with occupants and furniture!" . When he informed me that the following weekend they were going to return to attach sockets, switches, etc the I realised his meaning of "rewire" was different to the one I use.
Mine meant the whole job lot from start to finish, his meant just what I calls "First Fix", in fact when I use that term I include plastering some others might not.
Anyway the point of this tale is :- that bloke also told me that they had a devil of a job getting the tails into consumer unit terminals and needed to twist and twist and twist to get them in.
I asked him if the bare conductor had become a little shorter and he agreed yes he had, I asked him where that shorter bit had gone too. He did not know so I left him to work it out, I don`t know if he ever did realise that getting shorter by twisting meant getting larger in diameter and making it more difficult to fit (although against that we might make the spaces between the 7 strands nearer zero).