Radial Circuit in Garage - Change to Ring?

[SUNRAY]

As EFLI has said/implied, I think there is probably more uncertainly as to whether conductor(s) are 'clamped securely' if there are fewer 'small' conductors in a 'large' hole. That's why people often 'double over' single conductors, isn't it?
Kind Regards, John

I don't disagree
I'll give a scenario that the original wiring was a single solid wire doubled over shown red

and the black and green wires added later.

EDIT: But I still say getting lots of wires into one terminal is more likely to lead to subsequent failure if the wires are moved, such as fixing the accessory into place.

 

[JohnW2]

I don't disagree

I like double negatives However, I get very frustrated by the 'multiple negative' statements one increasingly finds on some websites, such as:

"Do not tick this box if you do not want us to not send you marketing rubbish"

How many times does one have to read such a statement (and maybe do some scribbling) before being sure what one should do to achieve the required result ?? ... and, even then, I sometimes 'get it wrong'!!

However, this is neither new nor restricted to 'marketing rubbish'. Many decades ago I took some major professional exams which consisted of several 'parts' (all of which one had to pass, separately). We all waited with bated breath for 'the letter' to come through the letterbox, and then found oneself reading something which said something very close to ...

"We have to inform you that you have not failed to satisfy the examiners in relation to the following parts of the examination."

Only really effectively a 'double negative', but I cannot tell you how many times we had to read that, whilst in an emotionally-disturbed/excited state, before we were certain whether we had passed or failed (overall) Anyway, after that diversion ...

I'll give a scenario that the original wiring was a single solid wire doubled over shown red .... and the black and green wires added later. .... EDIT: But I still say getting lots of wires into one terminal is more likely to lead to subsequent failure if the wires are moved, such as fixing the accessory into place.

It obviously 'depends' on the particular situation - particularly when, as you describe, further things are subsequently done. However, I still stick to my view that, in general, the 'clamping securely' of all the conductors is more likely when several conductors are 'crammed in' to a terminal than if there are just one or two conductors 'floating around, with lots of room to spare' in a large terminal.

Kind Regards, John

 

[JohnW2]

https://en.wikipedia.org/wiki/Circle_packing_in_a_circle

Sorry about this, but I don't like 'loose ends'!

I'm rather confused by this extract from the Wikipedia article (and this may help to illustrate my belief that a {mathematical} 'general solution' is not possible) ...

For N=6, the left-hand diagram (and 'the answer' it implies) is fine, since a 7th circle will fit exactly in the 'hole in the middle', in which case (as in the N=7 case) it is obvious that the diameter of the outer circle is 3 times that on the little ones.

However, looking at the alternative arrangement of N=6 in the right-hand diagram, I cannot escape the belief that it results in the diameter of the outer circle being slightly less than 3 times that of the little circles. The 'outer' little circles are not exactly aligned with the one in the middle and if one moved them such that there were aligned (in which case, outer circle would again be 3x the little ones) would require the outer circle to be slightly larger. That seems to mean that, as drawn, the outer circle would be slightly less than 3x the size of the little ones (i.e. the true 'optimum' is actually less than 3x), wouldn't it?

Any thoughts?

Kind Regards, John

 

[EFLImpudence]

and the black and green wires added later.

Surely that example is just poor workmanship and one or both of the other wires should have been doubled (or more than doubled) over as well.

 

[EFLImpudence]

Sorry about this, but I don't like 'loose ends'!

That's ok.

I'm rather confused by this extract from the Wikipedia article (and this may help to illustrate my belief that a {mathematical} 'general solution' is not possible) ...

View attachment 259082

For N=6, the left-hand diagram (and 'the answer' it implies) is fine, since a 7th circle will fit exactly in the 'hole in the middle', in which case (as in the N=7 case) it is obvious that the diameter of the outer circle is 3 times that on the little ones.

Yes.

However, looking at the alternative arrangement of N=6 in the right-hand diagram, I cannot escape the belief that it results in the diameter of the outer circle being slightly less than 3 times that of the little circles. The 'outer' little circles are not exactly aligned with the one in the middle and if one moved them such that there were aligned (in which case, outer circle would again be 3x the little ones) would require the outer circle to be slightly larger. That seems to mean that, as drawn, the outer circle would be slightly less than 3x the size of the little ones (i.e. the true 'optimum' is actually less than 3x), wouldn't it?

No, because the distance from the outer edge of the middle circle (wire) to the inner edge of the outer circle is equal to the diameter of the circles all the way round. You would be just rotating the diagram - or part(s) of it.

The diagram could be the same as the 7 circle example with one of the outer ring of circles (wires) missing.

What you are saying might apply to wires which could be compressed but the diagrams represent solid circles.

 

[EFLImpudence]

Think ball-bearings instead of wires.

 

[SUNRAY]

Surely that example is just poor workmanship and one or both of the other wires should have been doubled (or more than doubled) over as well.

The diagram is merely for ideas/indication.
I don't entirely agree it requires doubling over, these days apprentices are taught not to at my local college, I know not if that is todays 'standard'.
If I add some insulation to those wires:

And I feel the amount I've added is less than current 'standards',this shows very quickly how the copper can get pushed around and not be in the ideal place.

As to poor workmanship, debatable, one inserts the wires, tightens the screw (also remember not all screws have a lovely smooth bearing surface) and does the tug test. Nothing moves so it must be secure.
First resistance test. Measures perfectly acceptable as the wire is pressed against the terminal so it passes.

Months down the line the insulation has taken on a different shape due the summer warmth and being squashed. Winter comes along and everthing shrinks... just a little and suddenly the fault is there.

Where is the bad workmanship in all that?

 

[EFLImpudence]

Where is the bad workmanship in all that?

Do you not think the green wire in your original diagram would have failed the tug test?

 

[SUNRAY]

Do you not think the green wire in your original diagram would have failed the tug test?

Not necessarily, especially if done in cold conditions where the insulation is hard.

 

[JohnW2]

No, because the distance from the outer edge of the middle circle (wire) to the inner edge of the outer circle is equal to the diameter of the circles all the way round. You would be just rotating the diagram - or part(s) of it.

Thanks. Yes, you're right, and my 'intuition' was wrong. As you go on to say ...

The diagram could be the same as the 7 circle example with one of the outer ring of circles (wires) missing.

In practice, of course, whilst the Wikipedia's left-hand diagram is geometrically valid, it is only the one we are talking about (the right-hand one) which is relevant to 'conductors in terminals' - since one could not successfully tighten a terminal screw onto a bundle of copper conductors which had 'a hole in the middle' (or, looked at a different way, there would be no 'hole in the middle' after one had tightened the screw!).

Kind Regards, John

 

[SUNRAY]

it is only the one we are talking about (the right-hand one) which is relevant to 'conductors in terminals' - since one could not successfully tighten a terminal screw onto a bundle of copper conductors which had 'a hole in the middle' (or, looked at a different way, there would be no 'hole in the middle' after one had tightened the screw!).

Kind Regards, John

unless this happens:

Ingoring the fact the copper will distort to accomodate.

 

[JohnW2]

unless this happens: ....

Your conductors are so thin/pale (at least on my screen) that I initially thought that none were present! ...

Ingoring the fact the copper will distort to accomodate.

.. which, in practice, is, of course, a thing which one cannot 'ignore'. That being the case, the situation you illustrate would almost certainly be fine - only a very small amount of distortion of the top two conductors would be necessary before they both had good electrical contact with the 'central' conductor, as well as all the others.

Kind Regards, John.