Hi I often see on American programs like this old house, wiring connections using 'wire nuts' ( the twist on type not crimp, which I've seen used in appliances like vacuum cleaner's) they seem useful and easy to use but have not seen them here are they legal in this country? If so, why do we prefere terminal blocks?
Gordon
They are banned for the disgraceful fire causing murderous tat they are. They are one of the main reasons that the US has many times the likelihood of electrical fires and deaths.
Strangely, the other main reason is the dangerously low voltage used in the states. Higher voltage leads to better fire safety (electrical fires kill many every year). You would think it would, however, lead to better shock safety. However, it doesn't, as the lower voltage leads to lower quality hardware and a poor attitude on the part of users, who think of the voltage as safe.
Christian.
On 21 Apr 2006 05:54:41 -0700 someone who may be "gordonpuk" wrote this:-
Not any more, thank goodness. You may encounter them in conduit wiring done up to the 1960s. Best removed if encountered.
Wire and nuts are 2 things that should never go together
What is it, in your opinion, about wire nuts that 'causes' a fire? I have lived in North America for many years, used wire nuts extensively and have never seen a problem. Of course, if improperly used or incorrectly installed problems may result but that is not exclusive to wire nuts. The popular way here to join wires seems to be to twist wires together and slap a turn or two of insulation tape round the result. Hardly an improvement on wire nuts!
The problem is that the joining faces of the two wires are not in tight contact and light corrosion increases the joint resistance which causes slight heating. This in turn loosens the joint more as it expands and contracts as power is applied and removed which in turn worsens the corrosion and increases the resistance until such time as the joint overheats sufficiently to fail or cause a fire. Aluminium cable is particularly good at failing in this way.
Not much perhaps - but it is an improvement as the tape excludes moisture far better than a wire nut does.
If you think that's the popular way, change your friends.
Does that include DIY nuts ??
There's no way to know you have a good connection. With a screw terminal, you usually give a good tug on the wire afterwards. Occasionally it comes out because you didn't get it under the screw, but that's an easy check. If you give a good tug on a wirenut, you risk damaging the connection, even if it had been OK. They rely on the copper binding to itself when twisted, and completely hide the creation of the joint and the end result from view. They don't come close to the quality of connection from a compressive screw or crimp connection, which is what the rest of the world moved to over 50 years ago.
I've watched electricians (who have to quite regularly replace burned out crappy US sockets in computer rooms) redoing the wirenuts, and one of the wires quite often pops out when putting the socket back into the box. Doubtless there are also many occasions where a badly made joint doesn't completely fall apart before the face plate is on the box.
Other techniques are rather harder to get wrong in the first place, and much easier to instantly tell you got it wrong.
Well, that's certainly not popular here, but it probably is an improvement in some respects as you can at least see the connection before you tape it up. A wirenut is a bit like doing the same thing with a blindfold on, and only taking the blindfold off after you taped up. ;-)
Wire nuts are the spawn of the devil, *especially* in power installations.
Tim
FWIW they used to be called 'Screwits' or 'Midgets' and the larger ones were called 'Normals'...that was interesting wasn't it? You can still buy a plastic version today made by Wieland [I think]. Any road-up, on the subject of terminal or 'choc bloc' does anybody know where it says that you can actually use the stuff? AFAIR 99% of the blocks have polyethylene insulation which has a lower melting point than the pvc cable and thus compromises the joint [or so the NICEIC bloke used to say] and the only acceptable types were porcelain and brass ones for use in churches [still in the Wiring of Curches guide] and ones made of Nylon 66 or the high temp versions. But as usual I stand to be corrected , as happens most of the time!!
'Screwits' was a trade name. "Dogs bollocks" was another name, given the way a pair of them would dangle below a knot in the two cables they joined. I don't think they still have any generally accepted name now in the UK, given how long ago they vanished from the scene. "Wire nuts" is an American name which would not be generally recognised in the UK.
They have two faults. They're not gas-tight, and they're mechanically too strong a bond, relative to their contact force.
Gas-tightness is the ability to resist corrosion developing over time. There's a moderate force applied over a small area, so that the pressure is high. This keeps the joint sealed and moisture out. It's why IDC connections have replaced screw connections in telephony (low power, noise sensitive).
The mechanical problem isn't a problem itself, but it leads to a situation where you can make an electrically poor connection and not realise, because a mechanical tug test seems OK.
Then take a look at the US domestic fire statistics. These things are evil!
That, to me, is a nut with holes drilled through it so it may be wired to stop it turning. Bit like a split pin system.
I found some in my parent's loft (wired when the house was built in
1966). I replaced immediately with a 30A circular junction box.The message from "Dave Plowman (News)" contains these words:
Why? They get along like a house on fire.
Amongst which part of the UK population is "The popular way here to join wires seems to be to twist wires together and slap a turn or two of insulation tape round the result"?
Bodgers. The only time this is satisfactory is with low voltage single core signal wiring like telephone cable.
IIRC the trademarked name was Scruit; I rescued some glazed porcelaine ones from a house that was being rewired.
Owain
I could name one or two NICEIC registered electricians ...
Owain
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