are wire nuts vibration resistant? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: November 02, 2018, 02:26:08 am
content: I am watching a youtube video where someone replaces a crimp connector inside of a hand held circular saw with a electrical wire nut, such as you would find in an American outlet.Are they suitable for this purpose?

author: sokoloff
author_rank: Super Contributor
timestamp: November 02, 2018, 02:37:12 am
content: I would say they're neither vibration resistant nor suitable for that repair. I don't like them on stranded wire at all and even less so to join stranded-to-stranded.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 02, 2018, 02:46:49 am
content: I find them frequently in commercial saws so they apparently don't have too much problem. Also found in ceiling fans and washing machines. I have never had a properly installed one fail, but they are not always easy to install properly. Requires proper size of a quality wirenut and careful initial alignment of the wires and the nut. Three or more hands about the size of an infant with Hulk like strength would be useful in some cases.

author: Kalin
author_rank: Regular Contributor
timestamp: November 02, 2018, 03:15:19 am
content: If done correctly, it will be fine in that application. It does require some care and attention though. Both wires should be stripped to the same length and if using stranded should be lightly pretwisted by hand before applying the marrette. A small tape around both wires below the marrette after completion will prevent any tugging on the wires pulling the joint apart in the connector. Also using High quality and correctly sized connectors makes all the difference in the world when it comes to longevity and vibration tolerance.Source: Industrial Electrician: I use marrettes to make splices in equipment on a regular basis up to 600 VAC and in pretty harsh Canadian conditions, and the only failures I have seen have been due to either poor workmanship, defective connectors(Especially Wago style), or left too long in direct contact with Canadian winter (IE: enclosure left open)

author: ratio
author_rank: Regular Contributor
timestamp: November 02, 2018, 09:41:17 pm
content: Some wire nuts,B-Capsfor instance, have a live spring that expands around the wires as you screw the wire nut on. Makes 'em less reusable as the other type, but I've never had one rattle off that was correctly installed. Do be sure that you don't run them so far on that the wires poke out the top!

author: coppercone2
author_rank: Super Contributor
timestamp: November 02, 2018, 09:54:56 pm
content: I thought all of them had a spring? I think all the ones I own have some kind of coil inside the plastic. Is there a different type?

author: Kalin
author_rank: Regular Contributor
timestamp: November 02, 2018, 10:07:21 pm
content: They will all have some sort of metal usually with a conical screw thread but not all of them are a spring type. The spring is a nice thing to accommodate a wider range of conductor size but not necessary for vibration resistance.Sent from my SM-G965W using Tapatalk

author: james_s
author_rank: Super Contributor
timestamp: November 02, 2018, 10:12:29 pm
content: Good quality wire nuts that are properly installed will work just fine for this. Stranded or solid, if it's not a piece of junk, and you put it on right, you'll break the wire by pulling on it before the wire nut will come off.

author: coppercone2
author_rank: Super Contributor
timestamp: November 02, 2018, 10:40:16 pm
content: It just seems like since its twisted, the vibration can slowly loosen it

author: ratio
author_rank: Regular Contributor
timestamp: November 03, 2018, 01:25:56 am
content: They bite in pretty hard, the wire will have grooves cut into it. I've not had an issue in the last 15-20 years that wasn't related to the installation; & tugging on them one at a time generally catches those.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 03, 2018, 01:55:21 am
content: Not all wire nuts have a metal insert. I have come across many which are plastic only, and which are suitable only for low voltage, low power non-critical installations. So check and use good ones, which do have a helical coil inside, well attached to the body.In many cases a well installed wire nut is difficult to remove, and in some cases it is impossible without destroying the wires.Vibration loosens connections by a combination of unloading the joint and providing/allowing motion during that unloaded interval. The light weight of the wire nut and the contained wires means that truly incredible accelerations are required to remove the pre-load. Run some quick numbers with the torque you apply to a wire nut, the force multiplication that you get from the relatively shallow internal taper, the mass of the nut and wires and the vibration g's you expect to see. Even really severe vibration environments (satellite launchers and the like) tend to be only a few tens of g's. I would expect the circular saw vib levels to be a small fraction of a g except for the immediate period before the case is broken in a drop.

author: drussell
author_rank: Super Contributor
timestamp: November 03, 2018, 02:10:46 am
content: Quote from: coppercone2 on November 02, 2018, 10:40:16 pmIf a Marrette comes loose from the wires, it wasn't installednearlytight enough. When installed properly the wires should be virtually fused together, not to mention that when you twist the Marrette all the way on tightly you should be doing it hard enough that it should twist the insulated part of the wires together for strain relief also.

author: drussell
author_rank: Super Contributor
timestamp: November 03, 2018, 02:23:36 am
content: Quote from: CatalinaWOW on November 03, 2018, 01:55:21 amYikes! That is downright awful! Toss straight in the trash if you ever see ones like that!Certainly always use good quality connectors! (...and properly rated and certified if they're for mains or any kind of high energy circuit.)At first I thought you were meaning the original MARR two piece style ones with the setscrew, which theyDOstill make. They're more expensive but might be better to use in some circumstances and can be re-terminated more easily, typically with damage to a shorter bit of the end of the wire than the twist-on spring "wire-nut" type. I like to use those when joining 8ga or 6ga instead of the big blue sized twist ones, though those do still make a good connection.This kind:Edit:Marrette Wire Connectors Product GuideInterestingly, it seems that they discontinued the giant "size 3" ones of those set-screw type, but they do still make the smaller sizes.

author: German_EE
author_rank: Super Contributor
timestamp: November 03, 2018, 09:01:15 am
content: I don't know about vibration but here's a selection of connectors (including a wire nut) tested to destruction. I won't say which one wins as it will spoil the surprise.Here's another torture test

author: KL27x
author_rank: Super Contributor
timestamp: November 03, 2018, 11:09:19 pm
content: I have seen wire nuts inside of tools from the factory. I think they should be fine for a circular saw.I have soldered connectors inside of many power tools with a good amount of vibration, and I have only had one failure/repair, when I chucked an unbalanced mandrel in a die grinder. Some high frequency harmonic occurred and the case actually friction welded together. It took some good taps with a hammer to get it apart. While it was on, I touched a housing screw, and now I know why it nearly burned me. You could see the spot welds in the seams where the plastic fused. The grinder also had a crummy switch in it, and this pushed it over the edge.... So when it did this, the plug got about 200 years worth of starts and stops in about 20 seconds. The plug turned black. I replaced the cord and the outlet. Resoldered the broken wire and replaced the switch. Balanced the mandrel with a drill and a dremel, and all has been fine, ever since.

author: fredst
author_rank: Newbie
timestamp: November 04, 2018, 06:29:35 pm
content: I haven't seen a loose or heat damage one removing dozens of ceiling fan/lights, worst case solid to stranded connection. I'm not aware of any UL shake and bake requirements we just did pre assembly moisture conditioning. Pre twisting does improve the pull out force although qual testing requires just jamming them in and twisting them on. Source; pull testing hundreds of wire nuts on an instron during product development.

author: SeanB
author_rank: Super Contributor
timestamp: November 04, 2018, 07:57:10 pm
content: The only approved wire nuts here are a ceramic one, in 2 sizes. small and large, generally the small will fit up to 3 2.5mm cables, and the large will handle 2 4mm cables and a 2.5mm pigtail for the supply to a plug socket. Over 4mm you use a crimp connector instead, and this then is crimped to the cable with the right tooling. Mostly non insulated, you have a separate sleeve ( either heat shrink or a stretchable plastic boot) and generally overwrap with tape afterwards.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 04, 2018, 08:12:38 pm
content: The videos and other posts show clearly that wire nuts are more than suitable to purpose. The wire nut physical abuse video also clearly shows that they are difficult to install properly, particularly with larger wire sizes and multiple wires. This is where other connection types, which allow inserting wires one at a time, do have a clear superiority. Here in the US this superiority comes at a fairly steep price premium. That may be different elsewhere.

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: November 04, 2018, 08:21:23 pm
content: Much safer to use something like this :https://www.ebay.com/itm/30Pcs-Electrical-Cable-Connectors-Quick-Splice-Lock-Wire-Terminals-Self-Locking/282979179828?epid=2178455916&hash=item41e2df9d34:g:UsQAAOSwy81ZeLyj:rk:7:pf:0You can also buy a type that uses screws to tighten connection (don't know how you call them internationaly , but here in EU we call them line clamps).If you don't have any connector avaliable use good old Western Union Splice joint.

author: Monkeh
author_rank: Super Contributor
timestamp: November 04, 2018, 08:23:20 pm
content: Please, no, don't buy random crap from China and use it for your wiring.Or wire nuts. *dons asbestos suit*

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 04, 2018, 10:11:15 pm
content: Safer under what circumstances? Carrying current enough to melt wire insulation isn't good enough? Surviving many, many newtons of pullout force? Is there a source for this concern about the safety of wire nuts? What is the failure mode and what is the failure rate?I do agree with the concern about buying low quality copies of ANY configuration.

author: james_s
author_rank: Super Contributor
timestamp: November 04, 2018, 10:41:40 pm
content: There is no issue whatsoever with wire nuts. For some reason there are a few people in UK/Europe who don't like them, most of those people clearly having only seen pictures and never used one. As with any connector type it's possible to improperly install them, but used correctly I find wire nuts to be the most mechanically secure device available. If you need to repeatedly connect and disconnect then a screw clamping terminal block is superior but for more permanent connections a wire nut will hold the wires more securely and be more resistant to mechanical issues or loosening of the screw. I've never had a wire nut fail in my house, I have however had the screw clamp on a circuit breaker fail. It loosened up somehow over time and arced.

author: coppercone2
author_rank: Super Contributor
timestamp: November 04, 2018, 11:07:00 pm
content: How about the repeated cooling and heating of the wire nut causing it to loosen some how? Is that possible?In my mind a crimp is deformed mechanically so much that the effect is small. With a wire nut I am not sure, it seems mechanically different. Can it 'walk' off?Say it heats, some area loosens and oxidizes a bit, then when it tensions again from cooling the stresses are different because of the oxide layer. Then it keeps happening. I think a mechanical crimp avoids this by being gas tight.Say its exposed to a bad gas like H2S or something.

author: Monkeh
author_rank: Super Contributor
timestamp: November 04, 2018, 11:12:36 pm
content: Quote from: james_s on November 04, 2018, 10:41:40 pmAnd then there are those of us who have.I also don't like your plug design, outlet and box construction, breakers, voltage.. And yes, I have experience with using all of those, too.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 04, 2018, 11:53:47 pm
content: Quote from: Monkeh on November 04, 2018, 11:12:36 pmAll connectors fail occasionally. Either due to improper installation, manufacturing defect, or whatever. What are the failure rates? Anecdotal information is not data.Thermal expansion and contraction is an issue for any connector design. Some designs have an explicit and fairly free floating spring to deal with this. Others have a more implicit spring action. Screw terminals and wire nuts are in this class. Crimp joints have little if any. All of the connector types mentioned in this thread form a gas tight seal. Some with more area than others. Some with some control over the pressure exerted. There are reasons to hypothesize failure for all of these, but I don't have any information on the actual fielded failure rates. There is also reason to expect those failure rates to vary regionally due to climate and construction differences.I would really like to see engineering data rather than prejudice. I am uncomfortable with some aspects of European wiring, but readily admit that my discomfort is driven more by unfamiliarity than facts.

author: rhb
author_rank: Super Contributor
timestamp: November 05, 2018, 04:07:39 am
content: Buchanan crimp connectors certainly won't come loose.http://www.idealindustries.ca/products/wire_termination/terminals_crimps/crimp_connector_splice_cap.phpThere are a number of options for insulation including insulated sleeves and separate covers. And there's always heatshrink if space is tight.I've found wire nuts in a lot of tools. I wouldn't use one on a vehicle, but I've never seen one fail in a power tool.

author: KL27x
author_rank: Super Contributor
timestamp: November 05, 2018, 04:41:48 am
content: QuoteIf the proper nut is used for the wire size, the wire should be deformed and squished together. The threading will push the copper into the nut, rather than a crimper squeezing the crimp around the wire. The method of generating the pressure is different, but the end result is pretty similar.I don't know why a nut should ever fail in a house. I think the main concern in a circular saw is the vibration. "Pullout force," shouldn't be a factor unless you mean internally by vibration. The maze/gland has the job of preventing a pulling force on any connections.

author: drussell
author_rank: Super Contributor
timestamp: November 05, 2018, 05:19:27 am
content: Quote from: Karlo_Moharic on November 04, 2018, 08:21:23 pmOh my... GoodGODno... Those things are terrible!That kind of horrible thing is never allowed in any kind of permanent wiring installation anywhere here in NA, at least not that I'm aware of. I certainly would never use those anywhere, even inside some solid steel kitchen appliance or industrial apparatus that couldn't possibly burst into flames.

author: james_s
author_rank: Super Contributor
timestamp: November 05, 2018, 06:14:06 am
content: Quote from: CatalinaWOW on November 04, 2018, 11:53:47 pmThe European style screw terminal blocks are quite good, I've used them in quite a few projects where the convenience is nice. They are not as secure or reliable as a good wire nut though, I've had the screws work loose, wires can sometimes pull out, but if being able to connect and disconnect easily is important they are superior for that task.I'll still stick by my assertion though that anyone who says wire nuts are not reliable is either not installing them right or is full of shit because they're simply not any more problematic than anything else used for that purpose around the world. There are billions of them in service and failures are exceptionally rare, only time I've ever seen it is when box used outside has filled with water. If that's not the case then I too want to see data.Now one very seriously flawed part of the NA electrical system is the push-in backwire terminals that are all too common on residential grade junk. Those ought to be outlawed, the European screw terminals are far superior to those.

author: rhb
author_rank: Super Contributor
timestamp: November 05, 2018, 07:36:19 pm
content: Quote from: drussell on November 05, 2018, 05:19:27 amActually, most US wall receptacles currently being sold have a connection like that. It's packaged differently, but the principle is the same. It was up to 12 AWG, but now they only allow that connection for 14 AWG.

author: Monkeh
author_rank: Super Contributor
timestamp: November 05, 2018, 07:38:56 pm
content: Quote from: rhb on November 05, 2018, 07:36:19 pmFrom what I've been able to tell, most of them are pretty terrible. There are good spring connectors, and then there are bad ones.I will own up to having used them on one recessed outlet to power a TV, because it turned out the breaker was mislabeled and a long walk away.. easier to just poke it in than try and bend a live wire around those screw terminals.

author: rhb
author_rank: Super Contributor
timestamp: November 05, 2018, 07:54:46 pm
content: I'm not sure I've ever used one. I prefer to bend wires around screws. Though I have worked on outlets where they were used to add another circuit leg.

author: KL27x
author_rank: Super Contributor
timestamp: November 05, 2018, 08:21:26 pm
content: QuoteIf you can press it with a finger like in this picture, it is not the kind of connector I would go out of my way to put in a circular saw.Even a very small screw can generate a lot of force compared to that. Even solder and heatshrink would be better for vibration, IMO.