Do electricians have special powers?

No. They are obviously the right tool for the job.

UK must have funny fittings,AU general purpose power points will take at least four 2.5 sq mm stranded cables twisted together.

I find that twisting wires together makes the overall diam. greater, leavin g them straight ensures they fit. I too had the twisted wire curse making l ife difficult whilst replacing a pull cord switch. We have a lighting circu it dating back to the 70's where the loop in is done at the switches, so ea ch common terminal has 3 wires entering it. The more modern switch plates d on't have terminals to take 3 wires comfortably let alone twisted together. What I found in the pull cord switch was 3 wires twisted together what cou ld fit was pushed into the terminal and the screw tightened leaving at leas t one wire effectively only held on by the twisting not the screw. This was self certified as correct according to the documents presented to us durin g purchase.

Richard

That's a bit surprising since pretty well all lighting fittings are designed to accept at least 2 x 1mm.

The fuller a terminal is, the less likely it is to have problems. Cables are twisted to increase the diameter where a terminal is a bit big. Also the screw bears down on all the cable strands without going between with twisted cables.

As an apprentice, we were taught to bind undersize cables with fuse wire to increase the size. Three x 7/.029 stranded cables only just fitted a socket when untwisted.

I see a lot of new stuff has separate terminals for each cable, eg ceiling roses and some sockets. Better arrangement I suppose.

Any sensible objections to the idea of cutting one strand of each conductor short? If the strands are pulled out of the insulation and the cut made exactly at the end of it the cut end will retract into the insulation.

Bill

I would say the trick is to get the wire ends very straight (striaghten each with wide nosed pliers). On a full terminal don't try to insert them all at the same time - add the final one when the others are in place.

Once wires have been in a terminal a deformed a bit under screw terminal pressure, it can make them harder to get back in. If there is enough slack, stripping one back to some "clean" copper can help.

No but I swear that cables are prone to Obesity when released from screw terminals or holes in plugtops and sockets. I blame Quantum weirdness myself. they say the universe is expanding faster and faster, well it seems to affect wires as well. Brian

In the old days I sometimes resorted to tinning the ends, which contrary to what one might imagine, were more easy to squash into the available hole. Brian

Just doing the screw up to normal tightness will permanently deform the cores, if it didn't the joint would fail pretty quickly.

That is a bad thing, the joint will fail quicker if you tin it and then use screw fittings.

Brian Gaff formulated the question :

It is a really bad idea to tin the ends. The solder will evenstually settle due to pressure leaving the terminal loose.

Cutting out strands is a big no-no.

Why? Tell me exactly why that is.

Bill

Play it out in your mind. What would happen if you stripped a 7-ply cable down to 1-ply?

jgh

Global warming has made the cables expand.

If you were going to do it (and I am not suggestion one does) you would need to take careful note of the exact circumstances to factor in if you have left enough margin (i.e. allowing for other de-rating factors as well).

Something like a lighting circuit wired in 1 or 1.5mm T&E usually has ample spare cable capacity when the circuit is protected at 6A. A ring circuit with some sections in insulation however may already be close to its minimum nominal rating of 21A per leg to make a further 1/7th reduction most unwelcome.

Short answer - Yes!

I played a similar game with a three gang light switch where I could get two of three (or was it three of four) cores in but never the last one.

Took me bloody ages and some very constructive swearing.

It may be genetic, or part of some advance training course, but electricians seem to be able to do this easily where lesser mortals just toil and swear.

Unless, of course, like plastering bricklaying et al. the first few weeks/ months of training weed out those with the inability to fit far too much into too little space.

Cheers

Dave R

I said you could remove one strand.

Bill