Why do Americans (and others) choose wire nuts over reusable terminal blocks like Wago offers?
Do they offer any benefits? More current, longer lifetime,...? Or are there regulatory restrictions?
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The reason is inertia.
Wire nuts are easily available in stores. Everyone knows how to use them. Amateurs (homeowners) keep using wire nuts because they don't know of the existence of anything else because they are not stocked in shops and if they are, they are in the "obscure funky stuff" display.
Professionals keep using wire nuts because they have a proven track record of customer satisfaction and safety. That doesn't mean push-ins are bad. But if a professional is highly adept at doing installations with twist nuts, can do them quickly, effortlessly, and knows the result will be no callbacks, why would she start using something else? It's high risk and not much benefit. (Not that the lever nuts themselves are high risk, but that any changes to the highly rehearsed and tuned techniques of a professional create risks.)
Maybe cost too ... I buy the expensive clear Wago brand lever nuts. They are WAY more expensive than buying a bucket of mixed twist nuts. But I think there are cheaper push-ins available and I don't think cost is the main factor.
Because the big box stores haven't made selling these a priority. Let's face it if Joe-Average homeowner saw these first at big blue/orange/green and they were readily available, they would certainly be used more.
I have no idea why the big boxes don't sell these. I am sure some stores do but most don't and if they do they are on the bottom shelf - you know like the very very bottom tray.
That's it. They are definitely safer to use in outlet boxes for the average person and they are easier. If messing with 12g multiply this times 10. Joe-Average usually doesn't get his wires appropriately twisted when combining 3+ 12g wires. Joe-Average should use these. If the spring did have issues like the backstabs... It is like 3-4 mins to replace. I doubt this is an issue. Having 3+ wires without proper contact is a much much larger issue in my opinion. I have bought many a house where I open up an outlet and was like "how did this even work?" and then notice the melted plastic and black marks.
That being said I just wired another basement last week and used nuts haha. But I think its just because I have a big bucket of nuts. Probably be one of the last I use.
Anyone that has any safety concerns or fear that these might go out... the largest producer of canned lights use blocks. You would have to open up your ceiling to fix a "bad spring" and I have never heard of this ever ever happening.
Why big boxes don't sell them... No idea. I am guessing it cuts into profit margin on other things.
In addition - Probably the most common - potentially dangerous thing - for homeowners or beginning electrician is updating aluminum connectors with copper pigtails. When done properly the house is just as safe as an all copper house. When done wrong you get burnt aluminum improperly connected to the copper. My point here? Is that every town near me has changed the required to using the block connectors for pigtails - no exceptions for the purple nuts. So the last couple of house I did I bought exactly what was in the picture below.
In my experience, wire nuts are typically cheaper, occupy less space (such as in a cramped electrical box or with a low profile light fixture)(EDIT: as @DMoore points out, I may be using the wrong terminal blocks, as consensus is that they are indeed smaller than wire nuts in all cases. I'm leaving what I posted as it's from personal experience, but adding this note as a tip of the hat), and are just as re-useable as terminal blocks, with many of the same drawbacks (need to ensure the wires are securely in the device after insertion, limited to a reasonable number of wires per device, etc.).
I'm also hesitant to use terminal blocks for household wiring for much the same reason I'm hesitant to use backstabs in an outlet; Springs wear out and become a point of failure. If the terminal block is not spring loaded, then you run into the situation where you're holding a light fixture up while wiring it, and needing a third hand so you can operate a screwdriver.
EDIT: A valid point is to be made that the "3 hands" argument also applies to wiggle testing wire nut connections. It's still less awkward than using a screw driver would be, but it's not as bad as I initially made it out to be.
I have wondered the same thing among more differences in electrical standards and practices.
My hypothesis on wagos has two/three parts:
Due to bad design the backstab in the standard us outlet, where there is a single point of copper that acts as a mechanical lock, mechanical spring and electrical conductor, there is a high chance of failure when using this port.
Due to the similar mode of operation (push wire in hole) it may be incurrectly assumed that the same issues are present in wago connectors. Here however, the conducting element is pushed on the wire by a spring and a separate element makes sure it can't fall out.
Lower voltage / Higher current
Due to the fact that the us commonly uses 120v, opposed to Europe where 230v is the norm, currents in the US for the same load are doubled.
For the same terminal block, with a low but non-zero resistance, the powerloss in that part is 4 times higher in that part. This will heat up the terminal much more. Especially on a backstab the expansion and contraction of the connector will make a bad connection worse.
This is just hypothetical, so feel free to disagree.
It seems to me that the US has a much higher valuation of craftmanship in electrical work. The ability to make a proper wirenut connection or to bent the wire for a screw connection are valued.
This combined with much stricter rules on who is allowed to do electrical work keeps the old practices alive. (This statement seems to be false, see comments)
The standardization of outlets and switches may also play a role, I believe the design is pretty much frozen.
In the Netherlands there is, I think, much less faith in the capability of hired craftsman. There are less rules on who is allowed to do electrical work and there is no such thing (anymore) as a mandatory inspection of the electrical work by a homeowner. There are standards to which an outlet has to conform, but the actual design of the device is left to the manufacturer.
This combined with the high costs of labour has lead to easy to install wirenuts, outlets and switches.
The case for wirenuts
When properly made, a wirenut itself has no current running through it, it just makes a wire-to-wire connection by pressing them together. A wago-style bloc actually conducts the current itself and thus consists of a wire-to-nut and a nut-to-wire connection. So in theory a wirenut will have a lower resistance and lower heat-development.
When NOT properly made, however, a wirenut is no more than the wires loosely twisted together.
The case for wago-like terminals
It is very easy to install a wago-like terminal correctly, to the point that almost anyone can do it. Due to the per-wire spring it is less likely that the entire nut fails due to thermal and/or mechanical stress, only a single wire will get loose.
A final advantage is that it is trivial to add a wire (provided you have connection holes left) to an existing terminal.
I am not an electrician, but I have some professional experience in electrical work for high-current systems and a lot of DIY experience rewiring my house.
I would never consider using wirenuts, primarily for ease of use. Wirenuts may have a lower unit price, the extra time needed to install is more expensive.
When visiting this SE I am always surprised by the design of the outlets, with large exposed copper conductors, big screws and still the same, broken, backstab ports.
In contrast the sockets I've installed in my house have spring-loaded terminals and a molded inner cover making them touch-safe even without the coverplate.
Aside: your question says "reusable" but the Wago 2273 series push-ins in your photo are not reusable. The Wago 221 series lever nuts are reusable. The next guy inside this j-box will likely be me, so make his life a little better by using a Wago lever nut.
After you've been using wire nuts for years with no issues, you've learned to trust them and your ability to install them correctly, every single time. Nothing new can have this level of trust.
Many electricians that have never used a Wago lever nut never will. There's no reason, they'll tell you, because "a properly installed wire nut costs $0.01 and will never fail." They're right about not failing, about 99.9% of the time. The other 0.1% of the time they'll still blame improper installation. Unless you point out they personally installed that wire nut.
They're wrong about a wire nut costing $0.01, because they don't factor in their $1-2/minute hourly fee to "properly" install them. Lever nuts are faster to install, test, remove, and reinstall.
Everyone believes they know how to use wire nuts (marrettes). Most are half right. Using wire nuts properly means either:
a. stripping the wires to the correct length, holding them side by side, putting on the cap, and twisting the nut clockwise until "tight."
b. stripping long, pretwisting the wires with a pair of side cutters / lineman pliers, trimming to strip length, and capping "tight" with the wire nut.
The devil in the details is the definition of "tight." Manufacturers don't specify. Some electricians say "as tight as you can with your fingers." Whose fingers? Winged or non-winged nuts? Winged will obviously result in significantly more torque. Others say as tight as you can with lineman pliers. Held inline or perpendicular to the nut? Nobody says. Some manufacturers have produced videos (Leviton) showing barely finger tight. Most show that when sufficiently tight, a wire nut connection will have braided some of the insulation too.
An examination of the failure modes of wire nuts includes:
After witnessing just a few of these failure modes, anyone should recognize a) there is skill involved, b) the value of pull testing every wire, and c) pre-twisting. When pre-twisting, you can see and remedy most faults before the nut goes on.
The main reason is cost. Let's take this Wago 25 pack on Amazon, with
All that for $20.99. For contrast (mind you, 2021 supply variances have distorted prices a great deal)
As you can see, even with inflated prices, Wago is simply more expensive to source in the US. Wire nuts provide just as solid a connection (provided you twisted the wires correctly).
There's also the problem of usage. Big box stores don't like carrying esoteric stuff that doesn't sell (I have aluminum branch wires and use the connectors DMoore talks about, which are pricey and are only carried by one store). I can't say I've seen any professional electrician use splices, let alone Wago, over a simple wire nut.
I live in Canada so extending this to all of North America!
The reason I believe that wire caps are supplied over terminal blocks is certainly price, driven by customary practice.
It appears to be customary in N.A. to provide wire caps with light fittings. In order to meet this, they provide the cheapest and safest option.
I've lived in 3 countries, New Zealand, the UK and Canada, and spent a lot of time in Australia. When purchasing a light fixture outside of N.A. I hadn't received, nor expected to receive, wire nuts or any type of connectors.
I'm surprised this has not been mentioned previously, but speaking as a DIYer with over twenty five years of hand on experience in home electricity, I use wire nuts simply because I know that professional electricians uses them in my region (Canada/Quebec/cities where I've lived).
I mean... Let say I go to the store to buy hardware for my home project. In the alley, I see some product I know, and next to these, I see some alternatives products. Now, a few questions come to my mind:
See, being a DIY is sometimes about creativity, freedom and innovation, but at other times, doing it yourself mean you have to play by the book even more that professionals. Yes, that sums up to inertia. But do I have the luxury of being an early adopter (in my area, at least) on that matter? I dont think so.
Old habits die hard.
Using a regular wire nut requires a certain amount of strength and persistence; doing it properly was ingrained during trade-school.
The ol' "pull test" is significantly difficult to fail using a push-to-connect and if it does fail then toss out that connector.
Now that Wago's, backstabs, and push-to-connects have made their way into the market the average homeowner will buy what's easier to use, still screw it up, and an electrician will get to deal with the aftermath which solidifies the "they don't make things like they used to" cliché.
Don't forget that every locale gets to make their own rules about what's acceptable. Your neighbor could very well be allowed to use something which you cannot simply because your locale has not gotten around to allowing it.
In France, only lever connections like Wago are allowed. It means:
I’ve been using twist fasteners for sixty years. Most electricians transitioned away from crimp connectors pretty quickly once once reliable and approved twist fasteners such as Scotch Locks were available. Today is the first day I have heard of WAGO connectors.
Nothing is perfect if not installed correctly.