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In Brazil, electrical connections are almost always done splicing electrical cables by twisting the strands together and insulating them with electrical tape. Here is a video showing some of the connections the way they are done in Brazil. Terminal blocks are only used on some specific applications and wire-nuts are nonexistent here.

Here on DIY.StackExchange and elsewhere, I've seen criticism of that method and statements that wire-nuts are the way to go.

Is a stranded cable connection, twisted and taped as shown in the video, objectively any better or worse than wire-nuts/terminal blocks?

Luiz Borges
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    "almost always.." I very strongly doubt that's true in any building expensive enough to warrant a licenced electrician or an inspector. Be that as it may, you'll never get the strain relief of a wire nut in a hand-twisted junction. – Carl Witthoft May 16 '16 at 13:25
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    I'm interested in this "only tape" method and how it's done. I can't picture anything that would be anywhere near as secure as a simple wire nut, and electrical tape is a sticky, gooey mess. – JPhi1618 May 16 '16 at 14:31
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    https://youtu.be/Y9TrJhAGcoA – Luiz Borges May 16 '16 at 16:40
  • @JPhi1618, I was o phone and couldn't update my comment, the link above shows what I consider a properly done twist and tape connection. – Luiz Borges May 16 '16 at 17:57
  • For one thing, that video looks like it wastes 3 or 4 inches of wire per side/wire with all the twisting & folding & cutting some off, where a wire nut would take maybe 1 inch of stripped wire. I don't know how well wire nuts work with only twisted strand wires though, they do really bite into solid wires – Xen2050 May 16 '16 at 17:57
  • @Xen2050, my question is directed to cables (where you have multiple strands of fine wire) instead of solid wire. On solid/rigid wire I can see the advanted of mechanical methods over twist and tape, but on flexible cable I'm not sure if it is any better. If the really bite (as you said) on the wire, that might not be a good idea on cable. – Luiz Borges May 16 '16 at 18:14
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    A 'linesmen' splice is probably better than a wire nut and the last step would be re-insulating it with tape, after the leads are pre-tinned, wound correctly and then soldered together. But that's not what we're talking about. – Mazura May 16 '16 at 18:20
  • Thanks @LuizBorges for the video. That seems like it does make sense for wires that have relatively thin individual strands. I haven't worked with that wire in a home in the US (I'm not an expert at all), so I couldn't picture what you were talking about. – JPhi1618 May 16 '16 at 18:34
  • You're talking about house wiring, does Brazil not use solid wire inside houses? I've read twisted strand wires are used for flexibility, like in extension cords, why inside house walls? – Xen2050 May 16 '16 at 18:39
  • @Xen2050, that depends on preference of the electrician. My old house is solid wire and I think it is a pain to work with it. The house I'm building will be stranded cable (it is not twisted as you say, they are linear inside the sheating). The flexibility make it much easier to work and install receptacles, etc. Also, our walls are usually solid mansory (my house will have drywall too), with corrugated conduit inside for the cables. – Luiz Borges May 16 '16 at 18:49
  • Related: http://diy.stackexchange.com/questions/10144/why-are-wire-nuts-not-used-in-the-uk – Jules May 16 '16 at 22:01
  • Are crimp connectors, or terminal connectors available in Brazil? – Tester101 May 17 '16 at 01:57
  • @Tester101 Yes. Those terminais are pretty common. – Luiz Borges May 17 '16 at 02:43
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    Wire-nuts "are widely used in North America, but are not approved for use on low-voltage wiring in countries in the European Union and in many other countries." – JimmyB May 17 '16 at 10:52
  • Strain relief? I tape the insulated parts together to keep them roughly in place before trying to get the wire nut on. – JDługosz May 17 '16 at 18:22
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    I'm in the Netherlands, in the European Union, and I've learned using wire nuts in school. They're quite common, although I see more and more push wire connectors. I've never seen a taped connection in a professional setting and would consider one very unprofessional. – SQB May 17 '16 at 19:32
  • In my limited experience, wire nuts don't work great on stranded wire--the wire is too fragile. Houses are most commonly made of wood here, not masonry, so the fire risk is presumably higher here. In the context of several different interacting materials and systems, maybe the Brazilian method of connecting wire is superior in Brazilian-style houses. I've never been to Brazil, but based on travel in other South American countries, any technique that doesn't require specialized imported parts has a big advantage. – Phil Esra May 18 '16 at 07:18

8 Answers8

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Splice connectors such as US-style wirenuts and UK style terminal blocks are demonstrably better in nearly every way to the twist-and-tape method you describe.

  1. Wirenuts and terminal blocks are more resistant to mechanical failure due to heating/cooling cycles and the mechanical stress of installation.
  2. Wirenuts and terminal blocks are easier to inspect and test, even long after initial installation.
  3. Wirenuts and terminal blocks are easier to install CORRECTLY and require less training to do so.
  4. Wirenuts and terminal blocks can be quickly removed, and can be re-used without shortening the wire.
    1. Tape can be removed and the wires reused, but the process is labor intensive and messy because of the adhesive. It's easier to cut the wires before the splice, thereby shortening the wires.

So why are wirenuts not more common everywhere? Cultural bias and intertia. For example, wirenuts are not commonly used in the UK because an early wirenut product in the UK market had a design flaw and frequently failed, spoiling the reputation of the product. Terminal blocks became the standard by default. Because of this history, wirenuts are seen as inferior in the UK, when they are empirically not. They are just different than the commonly used terminal block.

I would argue the same is true for twist-and-tape joints in Brazil: it's how it was done in the past, and anything different is strange and therefore must be wrong. The only difference is that, at least for household wiring, wirenuts and terminal block are empirically superior to twist-and-tape splices.

Tester101
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longneck
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    Are you giving authoritative opinion in the bold line at the last paragraph? Because I am from Brazil, (and while I am not a professional electrician) I've done or witnessed dozens of electrical house instalations, browsed several local electrical material shops, and this is the first time i've heard of a wire nut. So it is not that the different is wrong, is that the different was never presented here. There are political, economic, (cultural too) factors that make said product not available at the market. So unless you have evidence to back your statement, don't spill biased opinions. – Mindwin Remember Monica May 16 '16 at 15:48
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    Today I went to the two largest electrical equipment stores in my area. I only found those kind of connector http://www.eletrorastro.com.br/ecommerce/media/catalog/product/cache/1/image/1200x1200/9df78eab33525d08d6e5fb8d27136e95/1/0/100132-100133-100134.jpg – Luiz Borges May 16 '16 at 18:00
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    @mindwin my comment may have been heavy handed, but it's still correct. And it doesnt apply just to Brazil either. The UK has the same attitude about wire nuts vs. terminal blocks: they use terminal blocks because the masses know terminal blocks and therefore anything else is perceived as wrong. The US is the same way in the inverse: terminal blocks are allowed and commercially available, but no one is trained on them, and therefore the masses come to the conclusion that anything other than wirenuts are wrong. It's just that twist-and-tape connections are also inferior in almost every regard. – longneck May 16 '16 at 19:45
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    No, it is not. Your boldfaced text is biased speculation bordering on prejudice. The things are ** just not available for purchase ** in hardware stores. We use tape because there's tape and nothing else. Professional electricians use tape. Some very specialized stores sell these things, but they are too expensive to buy, compared to tape. It is your bias versus two native points of view. Mine and @LuizBorges. – Mindwin Remember Monica May 16 '16 at 20:07
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    Just to strain it: wire nuts are not widely available in hardware stores in Brazil. And the few that do sell them have a prohibitive price. The point of the quality of the connection or the benefits of using it vs tape is not being challenged. Unless you cite a source proving that in Brazil: it's how it was done in the past, and anything different is strange and therefore must be wrong, please remove that line as it is prejudice. – Mindwin Remember Monica May 16 '16 at 20:12
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    @Mindwin I don't interpret the line the way you're reading it. The truth is that unfamiliar products tend to be less popular than the way people have always done a job, particularly in electrical work where safety is an important concern. The lack of availability isn't likely because of anything more interesting than the fact that when the stores try selling them, nobody buys them, probably because nobody knows what they are or how to use them. I'm British. if I saw a wire-nut in my local store, I'd buy a screw terminal by preference because I know how to use it. But I never see them either. – Jules May 16 '16 at 22:07
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    The U.S. uses terminal blocks extensively in commercial panel boards I have installed tens of thousands for small control wire to 750 KCM feeders. I noted this in the original answer. Wire nuts are more common here for residential. When you have hundreds of connections in a small area terminal blocks are the only way to go. When motor connections above 10hp most electricians start using split nuts & tape or compression fittings bolted together and tape (cambric + rubber+vinyl). – Ed Beal May 16 '16 at 22:53
  • This post has but one question: 'Is a properly twisted and taped connection* objectively any worse/better than wire-nuts?'*, which was answered by bullet point #1. IMO, it goes subjectively down hill from there. – Mazura May 16 '16 at 22:55
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    @Mazura, I don't think that it answers the question. A properly twisted (using the correct technique twisting with pliers and not just fingers) stranded cable (and not solid wire) isolated with high quality electrical tape IS indeed very solid mechanicaly, at least from experience. Almost all derivations and distributions of cables in Brazil are done like that for as long as cable existed. Without a proper test or more information, the question is still open. The one type of connection that is FOR SURE better mechanically is soldered twisted cable. – Luiz Borges May 16 '16 at 23:09
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    @Mindwin You're confusing the cause and effect. Wire nuts are not widely available, because they are seen as inferior. Stores stock what customers are buying, not the other way around. Lack of wirenuts in stores only proves that people don't like them. – Agent_L May 17 '16 at 10:05
  • Let us continue this discussion in chat. – Luiz Borges May 17 '16 at 17:38
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Is a stranded wire connection, properly twisted and taped, objectively any worse/better than wire-nuts?

I have not found any objective studies that compare a properly-made twisted splice of stranded cable with joins made using a US wire-nut, a UK terminal block or other systems such as the Wago 222 lever connector (and other makers equivalents).

Various similar types of twisted connections are used in specialized cases. For example NASA use a "linemans splice" in some situations. But they have very strict rules about how the connection is made. I imagine they are rigorous about inspecting and checking the quality of these connections before they are permitted to be used.

The main reasons that the type of connection preferred in homes in Brazil are not permitted in homes in other countries probably include:

  • It takes skill and regular practice to do properly.
  • It is very time consuming to do properly.
  • It takes dedication to scrap and redo connections that end up done poorly.
  • It is difficult to do properly in many real-life situations. For example in a dark area where space in a junction box is limited and the available wire length is short.
  • It is likely that some untrained people, perhaps householders, copying this type of professional connection, will do it carelessly and very badly and produce a weak and unsafe electrical connection.
  • It is relatively difficult to undo this join in a way that the wires can be included in another subsequent join.
  • The insulating tape may make it slightly more difficult to trace electrical faults to failures in the joins.
  • Poorly made joins will be concealed behind tape.

In the US, UK and similar high-wage countries, it probably costs less for an electrician to use faster techniques and tools than to spend time carefully making this kind of splice. This may not yet be the general case in Brazil.

RedGrittyBrick
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    I think your final paragraph might sum up the whole thing: cost of labor vs cost of material. And electrician wage is low enough that it might make no sense for manufactures to introduce something to save time at an increased cost. Add that connections are probably only inspected at terminals and industries and some commercial settings and it might explain why wirenuts and other types of connections don't show up here. BTW, we do have some types of block connections like the ones used in UK, but they are used on very thick wire, where, I think, twisted and taped connections wouldn't be possibl – Luiz Borges May 17 '16 at 14:00
  • If the slower twisted & taped method is legal, and if the electricians themselves are making the decision to pay extra money for wire nuts or blocks AND earn less money on the job (assuming they're paid per hour and faster = less $), then why would any electrician use them? Unless they are paid per whole job, and could increase their price and/or do more jobs in the same time... not sure how electricians work in other countries – Xen2050 May 19 '16 at 20:00
  • @Xen2050: In my part of the world, electricians are usually asked provide competitive quotations for specified work (e.g add a new circuit). Usually several are asked so that the quotations can be compared. Same applies to almost all business-to-business work too. – RedGrittyBrick May 19 '16 at 20:26
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There are a few cons to using tape: I think the most imperitive factor is that a good tape-job is difficult or impossible to verify (an inspector couldn't tell if 3 wraps or 4 were used). Also working on the wires later is often a goey mess, because tape breaks down. And tape is slower to install than wire nuts (time is more expensive than material).

Electrical tape cannot be used in USA as the only thing holding wires together; they must be connected by another means. A primary factor for instituting that law, is that workers or safety inspectors would be liable for failure to apply the tape correctly, which is hard to prove, and laborers/people are harder to collect restitution from than corporations (that have money). Also, having money allows corporations to push/influence laws. But, while I'm kind of cynical, I also appreciate the pros for wire nuts. I would prefer to see wire nuts in my home because they are (almost) fool-proof and any error/fault can be attributred to the manufacturer (part of the reason that manufacturers are abandoning this country, but that's another issue).

Also, having a good electrical system is not just a matter of having something that works- it's about organization and utility of the finished product; so that anyone who comes along behind the original electrician can easily modify or repair the system.

The only pro that I can think of for tape would be versatility. One product for any connection.

With regard to the twisted and interlaced connection (from the youtube video: https://youtu.be/Y9TrJhAGcoA), the tensile strength of this connection is good, but superfluous for conduction.

Ben Welborn
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  • It wouldn't let me do a 1 letter edit... i'll del these now – Xen2050 May 16 '16 at 18:05
  • I just looked everywhere for wirenuts and found it only on the eBay like site from Brazil (no physical store carries it, and no brand manufacture it here). Those I found online are brandless and probably chinese, so they don't have the warranty you mentioned from the manufacturers. They aren't expensive, but in all honesty I think the twist and tape method is safer than those brandless conectors. – Luiz Borges May 16 '16 at 18:10
  • @LuizBorges The skill level of the person making the connection and the quality of the connector (wire nut) are variable. I believe that the decision is your's in Brazil, but in USA you must use a connector. Safety should also include insurance. I doubt that the people of Brazil are as litigious as N. Americans, but in a worst case scenario, the company that produced a faulty product could be sued (implicating the electician would be difficult if he used a wire nut). So, I would suggest 3M for wire connectors, because they are not going out of business anytime soon. – Ben Welborn May 16 '16 at 20:19
  • No 3M connectors around here, but plenty of 3M and Prysmian electrical tape... I think that my question so far hasn't been answered, I agree that wire-nuts are easier to use, to inspect and to disassemble, but most electrical instalations are made to be permanent (or at least long lived), the assumption that they are more resistant to mechanical failure (when considering cable, that is what I plan to use) is open to discussion without a proper evalution of both methods. But from what I get so far, I will use tape, since I don't trust the brandless connectors that are sold here. – Luiz Borges May 16 '16 at 20:25
  • @LuizBorges are you unable to order anything online? Have you ever asked the hardware store (or whatever vendor) if they would kindly order something? I understand that you prefer electrical tape, but I don't understand the (general) trouble with purchasing electrical materials. – Ben Welborn May 16 '16 at 20:33
  • @BenWelborn, order it online from US would be prohibitively expensive (not to mention the long shipping time), the stores I went to said they "sometimes" have it, but due to low demand they don't restock it. Also the ones they used to have are brandless. In summary, the trouble with buying construction materials in general in Brazil, is that everything isn't fairly common is imported, expensive and hard to find if it exists at all. – Luiz Borges May 16 '16 at 20:39
  • @BenWelborn In my experience, purchasing cable connectors is more often than not a last-minute decision, usually because you're half way through the job and just realised you need one... – Jules May 16 '16 at 22:12
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    I have never heard the magnetism argument. I hope that's not really the rationale. Even with 10 centimeters of wire with a 2mm spacing and 30 amps only provides about 4 mN of opposing force. Equivalent to hanging a few paper clips to pull the wires apart. That might be enough if one simply laid the wires next to each other, but any wrapping would not be undone with so little force (as evidenced by Brazil not burning down from house fires). – Samuel May 17 '16 at 22:45
  • @Samuel I knew that this would be an objectable statement... I think that the more notable objection would be the lack of an iron core. However, considering stranded wire (about 20 strands each x 8 turns), the number of coils (N) increases. The picure of the brazilian splice (not there now) shows a tight C shape. B * gap = Mu * N * I B is in Tesla (10,000 gauss) gap is in meters (This is the opening of the "C ".) Mu = 4π * 10-7 N is an integer equal to the number of turns in your coil I is the current in Amps B = (Mu * N * I)/gap = (4π * 10-7 * 320 * 10A)/ 0.002m = 2T = (20,000 gauss). – Ben Welborn May 18 '16 at 14:33
  • @samuel... certainly it's not that powerful (due to the lack of an iron core) but considering votage spikes, and the amount of force nessessary to make one strand move, and the all important factor (time x force), better safe than sorry. The fact is, it's complex. Pigtail splices should actually cause attractive force... the inline splice on the other hand would not. – Ben Welborn May 18 '16 at 14:37
  • @Samuel supposing the N was not 320, but 16 (two wires 8 turns each), B = (Mu * N * I)/gap = (4π * 10-7 * 16 * 10A)/ 0.002m = 0.1T = 1,000 gauss. This is still a fair amount of magnetic force. How much force is necessary to move one strand of wire? How much electricity is necessary to blow a splice apart? Whatever, after considering your comment, I deleted the magnetic argument. But I do remember being told (at some point probably 30 years ago) that the pigtail splice was safer than inline (western union) because of magnetic forces... it stands to reason. – Ben Welborn May 18 '16 at 15:37
  • @BenWelborn I agree there is some force there, it's just not very much. I'm not sure why you're calculating for magnetism and stopping there, it's easy enough to get straight to Newtons. In any case, it's moot, but it is entertaining thinking about all the little invisible forces in our walls. – Samuel May 18 '16 at 16:10
  • @Samuel converting to newtons didn't really make sense to me... but I agree it's entertaining. 20,000 gauss = 2 Tesla = 2 Newton per amp of per meter... N total = 2 * 10A * 10cm? = 0.2 newtons... for 16 turns, 0.1 Tesla = 0.01 Newtons. Makes me want to get some iron filings and paper to see if I could see a field. – Ben Welborn May 18 '16 at 17:21
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A 7 twist solid copper wire has fair strength but over time especially with just tape the connection can loosen with big loads as the wires jump around. Wire nuts are normally used in the US on 10, 12 & 14 AWG wire.

Stranded wire will not hold up with out some kind of pressure connector a wire nut works great on stranded. With larger wire sizes Split bolts and compression fittings that are bolted together then insulated with Cambric, Liner less (rubber tape) and black tape (I use super 88).

The second problem with just tape it breaks down over time and or heat, Have you ever seen the black goo in the wires from the tape breaking down? Wire nuts allow more secure connections in a smaller area where you may have many connections coming in a box I would feel much better with a wire nut than several wires twisted and taped.

If the wires were also soldered maybe it could be a better way but solder melts and causes additional paths to ground so it is not allowed.

Much of the world uses the NEC national electric code as a wiring standard so I would say someone without a superior method is more of a hobbyist.

The only better way than wire nuts that I have seen is screw terminals but these take a lot of room and are normally only used in industrial control panels.

Dan Is Fiddling By Firelight
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Ed Beal
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    There seems to be good information in there, but it needs some formatting - it's very difficult to read as is. Some fancy bullet points would be great, but simply breaking it up with a few carriage returns would be sufficient. – FreeMan May 16 '16 at 14:37
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While i am a communications engineer [MSEE], i have wired a few houses, as well as done quite a bit of field engineering. What i would question with the twisted/taped connection, is whether the joint is "gas tight". Merely twisting the wires allows moisture and oxygen into the joint. Over time, particularly in a moist environment, this can lead to corrosion, resulting in a high resistance joint, and a potential fire (if it's power wiring). A "wire nut" tends to prevent this by screwing down on the wires, thereby tending to eliminate oxygen + water (and the resulting corrosion) from the joint. For something in a moist environment (possibly outside), as well as something carrying significant current (over 5 amps or so), my preference would be to solder the conductors together, and then either tape them - with the "fusing" type tape that melts together with itself - or, pot it in epoxy, with one of the 3M [Minnesota Mining & Mfg] or a competitor's product. Properly done, this should survive under water immersion over a long time. Cheers.

Rabbit20164
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    Wire nuts are mostly dry & open to the air, not counting expensive gel or "goop" filed "waterproof" nuts. Most houses aren't supposed to be underwater much anyway – Xen2050 May 16 '16 at 17:52
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    While the mention of water is out of place for this question, the "gas tight" observation is worth mentioning. While more often an issue when working with lower-voltage electrical connectors/connections, a properly installed wire-nut will create high pressure points between the conductors. When done correctly, these high pressure points will help keep out oxygen, which corrodes the metal and increases resistance over time. – JS. May 16 '16 at 23:54
  • I think the mention of water is entirely appropriate here. Water is everywhere in the atmosphere (as a gas), and is the single most important accelerator of oxidation and corrosion (and growth of mold on organic substrates) in a "normal" (not underwater) environment. A connection that increases resistance with age becomes a fire hazard. A gas-tight connection is an important attribute in electrical connections, and this is an instance in which wire nuts and terminal blocks are probably superior to a mechanical splice, IMO. Even tape-wrapped is likely not be be gas-tight. – AndyW Jun 21 '16 at 17:32
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The main advantages to twist-on wire connectors are ease of use, and time required to make a splice.

Making a reliable connection with twist-on wire connectors is easy, only requiring three simple steps.

  1. Strip the wires
  2. Put the connector on the wires
  3. Twist until secure.

A twisted splice is a bit more difficult, requires a bit of practice to get right, and may require multiple types of tape.

Since making a splice with twist-on wire connectors only requires three simple steps, splices can be made quickly.

Twisted splices are a more complex, and so require longer to make up.

One additional advantage to twist-on wire connectors, is that you can use them to connect more than just two wires. Most twist-on wire connectors allow you to connect four or five wires together, whereas a twisted splice only allows two.

Tester101
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I use "butt connectors" for every application. Tape eventually wears out like other have mentioned. Butt connectors are those that get crimped through a little metal tube (usually) making the connection very secure. I have never had a problem with them coming out. Good luck!

nikon0iT
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Hm. Different strokes for different folks... In my country, terminal blocks are mandatory. So, to me, THAT'S normal.

However, a 'butt connector' or other crimped connection is fairly solid. I´d like to point out that a proper lineman's splice works fine for solid copper wire, as far as I'm concerned, insulated with a couple layers of heat shrink tubing.

As for stranded, same thing, but soldered so it doesn't unwind. And I've found wire nuts (found inside US manufactured equipment) broken (overtightened?) or had them break apart as I respliced wiring.

You can prolong the life of plastic tape insulated splices by rubbing them all over with a hot soldering iron. The bits tend to fuse together, and don't come undone when the adhesive dries up. However, I prefer heat shrink tubing.

BTW, are wire nuts good for 40 Amps? I use terminal blocks for that current regularly, and, if properly tightened, they work just fine.

Cheers, staqUUR

staqUUR
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  • The biggest wire nut's i've seen can can do 2/10 or 3/12, so 30 Amps for a splice, 20 for a branch. On larger wires, split bolt is the closest option in terms of convenience/placement. – WorBlux Feb 20 '18 at 22:19