Why are “Wire Nuts” not used in the UK?

Question

I have never seen a wire nut used in the UK, but they seem to be very common in the USA, why?

Answer 1

One possible reason provided by Ideal Industries in This article

Although very much the connector of choice in North America, the twist-on wire connector remains a largely untapped resource in the UK electrical market. Unfortunately many electricians still associate them with the poor-quality ‘screw-it’ wire nuts from the 1970s; manufactured from ceramic, these had a tendency to crack very easily and expose the wires, leading to safety hazards.

Though it looks like Ideal is still trying to tap UK twist-on wire connector market, with the new Twister® PRO (which to me looks just like a regular wire nut, aside from it being multicolored).

Answer 2

Not sure about "why not" in UK (although Tester101 seems to have a good explanation [as always]), but there is a trend in US, at least in the DIY community to use the new side-by-side connectors

The overall connection is wider, but I find it easier to flex the bundle toward the back of the box, especially when there are three or four wires. Also, there is tactile feedback that the connection of each wire is solid and less chance that one of the wires has a loose connection as it might in a twisted bundle.

Finally, it generally needs less of a stripped lead, which is helpful if you need to snip the end for a new connection. Sometimes cutting the twisted lead leaves a pretty short wire to work with.

Answer 3

Building Regulations Part P in UK does not specifically ban or recommend using screw terminals in the UK. It goes to mention, that during joing wires they should be joined in the terminal of a switch/contact or to use appropriately certified equipment that is relevant to the job!

There is also an a section for old building compliance that may be encountered during renovations and they show some bad and good ways of doing certain things but do not mention anything about joining wires.

• I have noticed that in every electrical installation i work with in the UK there are always block connectors used. I even took apart some old lighting made in Birmingham in 1990 that used ceramic block connectors for joining 220V to ballasts.

• When I did some electrical certifications in South Africa, examples of connecting wires used plastic block connectors. But, allot of light fittings I installed; for example ceiling fans - were supplied with screw nut thingies and I just used those. But other halogen type lights had block connectors.

• It is interesting though that during a short period in Poland - most of the wiring i worked with (in pre-WWII buildings) they used some sort of soviet ceramic screw caps and connectors were scarce. Today however.. You can only buy plastic block connectors and those screw things are frowned upon. You cant even buy them at the whole sellers, just eBay if you desperate.

I have never seen any regulation banning the use of those connectors- But in my own experience I ALWAYS questioned how long will that wire actually last screwed in freely like that? And i preffered to use block connectors for piece of mind!

If you interested in more building regulations please click here (UK)

Answer 4

Twist-on connectors

The Wikipedia article on twist-on connectors suggests they were outlawed in the UK 50 years ago. No references are given. It is suggested that 50 years ago the ("Scruit" brand) twist-on connectors were made of ceramic and were liable to crack and expose the wires.

UK Electricians are a conservative group. Vendors of novel products have to go to considerable length to persuade them that their products meet the relevant legislation.

An Ideal Industries Inc. catalogue says

Conforming to BS EN 60998 Twister® wire connectors fully comply with BS 7671:2008 (17th Edition Wiring Regulations).

However, it isn't uncommon to see strenuous efforts on the part of manufacturers to persuade UK electricians that novel products meet regulations. E.g. Wagobox and Ezybond earth fasteners Some of these novel products more or less disappear from the market within a few years, others succeed.

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Screw-terminal-blocks

In the UK, electricians almost invariably use screw-terminals.

^{ruler is marked in cm with mm subdivisions}

The white translucent screw-connector block in the foreground is a typical example. This one is rated for 5A. Other sizes are available for different current ratings.

An electrician left behind the other connectors in this picture. I suspect they were used for temporary connections during installation. I've not seen any in a completed installation (but I'm only a householder not an electrician, so have very limited experience)

The "Marr No.1" connectors at back right look superficially similar to US wire-nuts but are very different. The metal insert is removed and a grub nut is used to clamp the wires, then the plastic insulator is screwed over the connection.

The "Legrand 10mm2" connectors at top left may be for higher current ratings. Note that the plate that presses on the wires is arranged so as not to exert any twisting force on the conductors. Perhaps this avoids damaging stranded conductors. It certainly prevents the conductors being pressed to one side of the screw and therefore not being securely clamped in place.

An obvious advantage of these connectors is that the wires can be removed intact and should usually not need trimming before reconnection. I have the impression that in the US, wire-nut connections are often removed by cutting the wires, which may leave progressively less and less wire available in the junction-box or back-box for remaking connections.

When more than two wires are to be joined, a slightly different type of screw-connector is used:

Answer 5

Tester101 addressed your "why not in the UK?" question. As to the "why in the USA?", I believe it's because wire nuts are easy to use, cheap, and occupy little space in the box.

Even an amateur can create a good splice with wire nuts. They don't need to learn to pretwist or anything: just line the wires up, jam 'em in, and twist like your life depends on it (hint: it might). Then hold the nut and give each wire a tug to make sure the nut grabbed it good. Got it wrong? Try again, no muss, no fuss. Really mangled things? Cut the ends off, strip a bit more, and try again. It's a lot more forgiving and reliable than any similarly cheap alternative.

Answer 6

They are also common in Belgium, if that adds anything. I found the old ceramic ones in my house and have used the modern quality ones for wiring lighting circuits very effectively. Simple to use and the house has not burnt down yet after 5 years so appear to be safe.