ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Twist conductors?

There's a regular debate over in the general U.S. area about whether to pre-twist conductors when using a wirenut.

So let's ask a similar question of those wiring British devices with their rather different terminal arrangements to American fittings.

When connecting multiple conductors to a switch or socket terminal, do you twist together first?

For closed types I like to get all the strands into the connector, and twisting (where possible) each wire seems a good way of doing it neatly. I'm not so keen on twisting all the wires together as that tends to shorten but fatten the length inserted.

To my mind the brass screw in threaded U style rose junction box that we have in the UK don't favour twisting; the cables compact down better without twisting allowing the grub screw to engage further.

Storm in a wirenut?

Gideon.


[This message has been edited by gideonr (edited 02-28-2005).]

Paul,
I've always twisted any wires that I've worked with.
The exception would be the larger sizes and Aluminium wires.
One aspect of Electrical work here, that annoys me, is where two wires feed a Surface-mount MCB base on a Switch-board panel and the wires aren't twisted together.
It's not the shock aspect of replacing the base live, but if the wires are carrying any sort of load, it makes for a bit of sparking.
In my opinion, pre-twisting gives you a better connection between the wires and also lessens the likelihood of cutting into the strands of the wire with a terminal that only uses a screw to hold the wire strands in the terminal body.

I never saw a conductor twist. Hmmm.

They prefer the watusi!

Good point, the terminals on most modern ceiling roses are pretty small, but then they provide enough terminal positions for one conductor per hole in most situations. You only have to double-up if you want to parallel a second light, run a second thru-feed, etc.

I think there's also quite a difference between terminal styles on other fittings which can affect this. Compare the types where the screw clamp down on a small plate versus those where the end of the screw just goes directly onto the conductors.

Well,
I'm sorry for the thread-jack here Paul, but I have a little, related question:
Where your terminal has enough space, after you have twisted the conductor, do you bend the wire back on itself, to fill the terminal tunnel?.

Not a threadjack at all -- It's a very good related question.

It depends on the terminal type and the conductors involved. On some types of socket, for example, if it's a spur or the end of a radial with just one 2.5 sq. mm conductor per terminal it can hard to clamp the wire properly without doubling it over. (Our 2.5 cable in twin-&-earth style is always a single, solid core.)

That's what I meant Paul.
It has been a convention here for years with stranded conductors that if you do have room in the tunnel to have a doubled up twist, you should do just that.
I think it comes from the strips of connectors, where there were no plates shielding the wire strands from the screw as it came down on the wire.
Driving a screw into the wire would cause it to eventually break and fail.

depends on how good the fit is i think.
I always twist my cpc's incase of terminal failing leaving them loose or out of the connection all together, by twisting them you ensure a better chance of the cpc remaining continuouse throughout the circuit,the failiure could arise at the first connection of a bank of 20 lights,
and no one would ever know the 19 other lights where not earthed (until next tested of course)where as they would soon know if there was a phase/neutral to pop out of its home!

quote
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by twisting them you ensure a better chance of the cpc remaining continuouse throughout the circuit,the failiure could arise at the first connection of a bank of 20 lights,
and no one would ever know the 19 other lights where not earthed (until next tested of course)
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Surely this is the reason why we carry out R1+R2 and measure zs to check earth loop at furthest point on the circuit. Problem with twisting you can stress the conductors specially this silly single stranded stuff, have seen more damage done by twisting and bending conductors than the terminals of the accessories do.