Wiring mains socket

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I can’t see why a twisted single pair shouldn’t be done, the electricity won’t give a hoot about it, and there will be enough area between the two and the hole and screw to make it a good contact. I’ve done a trial today with a short piece of 2.5 mm twin & earth, with the two of the live ones twisted, and the two ends of the neutral ones folded back, the twisted pair went in quite easily, but the folded back pair were quite awkward to get in with the screw near to falling out. I screwed them both down as tight as I could. When I took them out, I could see good amount of contact on one of the live wires and about the same amount of contact spread over the top folded back one.

The pull and fallout of the wire over three and five years, doesn’t really prove anything without a regular record of temperature changes, vibrations that may have affected the installation, and knowing how tight the screw was in the first place, you have to remember that brass expands more than copper does at the same temperature, so that can have an effect also. I have changed many sockets in my time, and have hardly found any that have come loose enough to be a problem, let alone falling out, but workmanship in the first place can make all the difference.

Regards Nick.

[HollowpointParticipant @hollowpoint]

I am not an electrician by any measure but I have done plenty of sockets. I don’t like the twisting method. I find that they come loose more easily. I always do a u bend IF the hole is big enough. If not they go in straight.

Speaking of horror stories. I moved home a couple of years ago to a house that was built in 1929, which I have slowly been renovating. The electrics here are horrible! None of it makes any sense whatsoever! Even the electrician struggled to identify how everything was connected up! It’s only through the renovation work that I am beginning to understand.

One small example. I changed one of the light switches recently, which was an ancient bakelite thing. The wires hadn’t even been screwed in! Judging by the layers of paint and wallpaper stuck behind it, and the black soot from the arcing, I would estimate that it’s been like that for 50+ years! 😱

[Ian McVickersParticipant @ianmcvickers56553]

Normally its better to double over the solid core and terminate that way. I wouldnt recommend twisting the cores together as it could lead to broken cores if the cores had to be separated for testing at any point.

[SillyOldDufferModerator @sillyoldduffer]

OK, I looked it up!

BS7671 does not say either way.  However, Regulation 134.1.1 is “Installation must follow manufacturer’s instructions.”

“Don’t twist” is implied by these MK and Scolmore instructions: they don’t mention twisting as an option.  Twisting is not expressly forbidden by them, even though BS761 enjoins us to  “not twist the strands of a stranded conductor before inserting it into a terminal, unless the terminal manufacturer specifically permits it.“.

Scolmore   “Cables should be prepared to the appropriate lengths (as stated within these instructions) so that the conductor reaches into the terminal, and the circuit protective conductor is the longest. The terminals should be tightened to their appropriate torque value. Do not over tighten.”

MK

IET GN1 says  “You should not twist the strands of a stranded conductor before inserting it into a terminal, unless the terminal manufacturer specifically permits it.“.   GN1 does not forbid twisting solid core cable.  However, twisting solid core is considered poor practice. “Solid (single-core) conductors are not intended to be twisted before insertion into a terminal.”

Comment:

The guidelines aren’t black and white.  Nonetheless, strong evidence that trainers considers twisting to be bad practice, the concern being the copper might be scored,  stressed or unevenly clamped.

I note the emphasis in the guidance and manufacturers instructions on getting the torque right.  No figures given – just “don’t overtighten”.  And also the expectation that electricians will read the manufacturers instructions, not just rely what they were taught in their youth.   Apparently some terminals are designed to take twisted wires, which changes the guideline.

The worst wiring I’ve seen was all in domestic homes, the best in warships.  They’re done to a much higher standard and inspected, or should be!   Computer rooms pretty good, though one was found dangerously wired with phases mixed inside an aisle.  Aircraft and industrial wiring are outside my experience.

Dave

[MacolmParticipant @macolm]

What I have done for many years is to fold the wire back if there is going to be enough room in the connection hole. Then I insert the doubled over connection(s) such that the clamp screw bears on the free end(s), which protects the active run of the wires from being partially severed if the screw is over-tightening or there is a subsequent tug on one of the wires.

My experience is this avoids connection problems.

[duncan webster 1Participant @duncanwebster1]

7 sockets checked, some never been touched for over 30 years, none needed tightening. I’ll carry on when my knees stop aching, getting down that low is for younger people.

[Author]

Posts