"Backstabbed" wiring: bad rap?

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Pete C. wrote:

You have not explained how surviving 30,000 specified operations and remaining functional is not a pass criteria.

Every manufacturer current-time trip curve shows an acceptable band. I have no doubt UL specifies a similar band (ie max and min acceptable clearing time at 200% of rated current). Tripping at too low a current is also not permitted. You really think the electrical industry would allow fuses/breakers to open at too low a current?
What UL standards have you read?
--
bud--

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On 8/21/2009 6:14 AM Pete C. spake thus:

I've watched this argument devolve here for a while now. Although I don't know what exactly UL uses for their test criteria, I find it very hard to believe that they would approve devices that only "fail safely" but that do not function properly at that point of failure (i.e., breakers that trip at significantly lower current than rated, switches that no longer switch, etc.).
I think the burden of proof in this case is on *you*.
--
Found--the gene that causes belief in genetic determinism

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David Nebenzahl wrote:

The burden of proof is on the person falsely claiming to be posting a UL test standard. No reputable testing laboratory would attempt to test to an incomplete test specification such as what mr bud has posted.
Remember was chartered to do product testing for the insurance industry, not consumers. Insurers do not care at all about the quality, functionality or value of a product, only if the product presents a safety hazard that could lead to an insurance claim.
Circuit breakers are designed to and allowed to trip at a lower point as they wear from multiple trips or age. They are not allowed to trip at a higher than specified level. A "weak" breaker is a common failure and does not present any safety hazard so it is not of any concert to insurance underwriters nor to their testing lab.
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Pete C. wrote:

Apparently Pete wants all 35 pages of UL20.
My original point was that, contrary to what had been stated, UL tests for some products do establish whether a device will "function properly". IMHO remaining functional after over 30,000 operations at or above rated voltage and current demonstrates that.
I would have no trouble designing tests for the 30,100 operations which I took from UL20. I would also have no problem determining if a switch passed those tests. (The standard has additional details on these tests and additional requirements.)
Pete has not said why he couldn't figure out the tests or whether a switch passed. (But that was not my intent anyway. I don't care if Pete can't figure out how to make the tests.) Pete is welcome to look at his copy and say what UL20 requires. I eagerly wait.

The foregone conclusion results in denying the evidence?
Whatever the origin of UL it is, frankly, laughable to think that the electrical industry would allow the present UL to list products used in the electric power industry that have not been tested to "function properly". Like for instance fuses, circuit breakers, motor starters, switches, receptacles, GFCIs, AFCIs, ....
From the UL "white book": "UL and its subsidiaries operate facilities throughout the world for the testing, certification and quality assessment of products, systems and services." Note "quality assessment".
Take a particular category, fuses. A fuse could itself fail safely (or operate but out of time spec) and still allow great damage, including fire and explosion, downstream. It could also be the difference between an electrician walking away from an event and severe injury or death from arc flash. (I believe even insurers might be interested in that.)

Cite.
Still missing - the UL standards you have read that had nothing "to do with non safety durability".
Also missing - the "proof" David asked for. My source is UL20.
--
bud--

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Note that it is no longer approved for anything except AWG 14 conductors. Code once permitted the use of AWG 12 conductors in backstabbed connections, as it once permitted aluminum conductors in branch circuits and various other practices and materials that have proven in experience to be less safe than originally believed.

If installed properly _and not disturbed_ it's unlikely they'll have much problem. OTOH, if a backstabbed receptacle or switch is removed for any reason, simply the act of moving the device can loosen the connections enough to cause trouble.

I'd consider the de-listing of AWG 12 conductors to be sufficient evidence.
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On Sat, 15 Aug 2009 08:44:23 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Solely anecdotal, but seems like quite a coincidence that I've had problems with them staying connected, particularly in receptacles that received frequent use (not taking out and working on, simply plugging and unplugging of appliances). As a previous respondent said, if done correctly and not disturbed... But if "anecdotally", merely using the receptacle a lot in the manner intended is enough to cause such disturbance, well, then it's not functioning as intended.
Now, I don't have non-backstabbed ones with which to compare them, but I can't fathom that a non-backstabbed receptacle would have done the same.
My amateur and anecdotal .02 worth.
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I've seen several problems with backstab sockets, but few or none with wrap around the screw types.
--
Christopher A. Young
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<stuff snipped>

I've had two backstab failures, one near a disposal where the switch was mounted on an outside wall and another on an inside wallswitch. I think the thermal expansion/contraction plus the disposal vibration did the first one in. Not sure why the second one failed. It's an indisputable fact, though, that there's much more connection area in a screwed down wire than there is with a pinch and grab kind of connector.
If the grabber is hard enough to bite into the copper to make a connection, it's most likely strong enough to bite through it *eventually* if helped by vibration, thermal forces and even the simple repeated toggling of the connected switch. Once arcing starts, no matter how small, corrosion and failure are likely to follow. More connection area in the screw connections means less of a chance of arcing or pulling loose. Also, it's very much harder to see a bad back stab than it is to see a wire not completely under a screw. I'd agree that the delisted AWG 12 is a strong hint that anecdotal evidence has added up to backstabbing being a bad idea, both with people and electrical devices.
BW
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Why take the risk? Is the extra two minutes required to pig-tail the ends and screw them down too much?
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I agree. Why take the risk? But have you ever see a klutzy newbie try to bend a wire loop or screw down a solid copper wire? I'd say fully half the rank newbie work is not fully under the screw or formed into the proper curve and is destined to work loose. I'd say that reason and the "time is money" contracting rule is why backstabbing got started.
Never on my own work, not after trying to trace that damn intermittent in the backstabbed disposal switch, but I can see why some contractors do it. I think it's one of the things that separates the pros from the tyros. Just like lining up the two screws on a switch faceplate so they are in the same orientation. (-: I grew up next door to an old-world craftsman of an electrician who helped wire the NYC subway system. His work is still in use today. Quality work lasts. But I digress.
A much more critical newbie error is to cut into the wire while stripping it which is a risk for either sort of connection method, screw or backstab. Ah, for a nickle for every time I've seen or accidentally done that myself!
Newbies and wire nuts don't mix well, either. Stripped end of wires too long, too short, wrong size nut, wrong mix of wires, twist not twisted enough. There's no end to sad tales with wire nuts in the hands of the inexperienced. My favorite is three wires under one nut with a virtually untwisted center wire that pulls right out on the first tug. I am much more concerned with bad wire nutting than with backstabbing.
-- Bobby G.
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I found problems with wire nuts also in my lighting. On several ovehead light the wires just pulled out of the nuts when I pulled them down for inspection. I also found 6 lights, two in the bathrooms and four outside that did not have J boxes They were just screwed to the wall withe the wirenuts tucked inside the wall. None of the light fixtures were grounded. I later heard that the electrician only did the electrical rough-in. The unskilled labour installed the lights and outlets.
Jimmie
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On Sat, 15 Aug 2009 17:11:02 -0700 (PDT), JIMMIE

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<stuff snipped>

<<I found problems with wire nuts also in my lighting. On several ovehead light the wires just pulled out of the nuts when I pulled them down for inspection. I also found 6 lights, two in the bathrooms and four outside that did not have J boxes They were just screwed to the wall withe the wirenuts tucked inside the wall. None of the light fixtures were grounded. I later heard that the electrician only did the electrical rough-in. The unskilled labour installed the lights and outlets.>>
The same crew must have wired my house!
-- Bobby G.
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On 8/15/2009 3:01 PM Robert Green spake thus:

Since you mention it, this is certainly a potential source of frustration to anyone doing wiring, newbie or not.
I bought myself a really nice automatic wire stripper--the kind that strips the wire in one squeeze, made by GB (Gardner Bender). Very well-made tool, very useful. Except that it doesn't always strip the wire correctly. I actually returned the first one I bought because of this problem, but it seems to be due to inconsistencies in actual wire diameters between cables that are nominally identical (#12, for example). So sometimes it strips perfectly, but other times I have to go to the next-smaller set of teeth, which can nick the wire if you're not careful.
When this tool works correctly it's an absolute pleasure to use: put the wire into the right set of teeth, squeeze, and the insulation is ejected like a shell casing.
--
Found--the gene that causes belief in genetic determinism

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<stuff snipped>

I had a cable stripper that was set perfectly to strip RG6QS for the compression connectors I use. It was perfect but a buddy spun it backwards, the blades popped out and all the king's horses and all the king's men couldn't put it back together. A good cable stripper is a very helpful tool, indeed, and can save tedious hours of hand work on a big job.
I bought a pair of Klein Romex strippers that cut it like butter and removes the outer wrap and the inner insulation on both conductors in one operation. Works great when new, not sure how it will work after wiring up a house and the blades get duller. As you point out, though, not every roll of wire is created equally or exactly to spec so I check every new roll to see if it's nicking the wire.
I replaced all the switches in my house with X-10 remotely controlled ones and far too many of the switch wires broke right where the insulation had been stripped and the wire nicked. One wire broke off so short I had to pull the box and gouge out the plaster to repair it. Of course that meant redoing the attendant plastering and painting. Yuck.
-- Bobby G.
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On Sun, 16 Aug 2009 00:53:45 -0400, "Robert Green"

If that is the stack of metal plates with a couple razor blades in it, there should be a tool included to set the blade depth. It is a metal rod with fly cuts at the proper depth. Clamp it in the stripper, set the blades to just touch the rod and tighten up the screws holding the stack together..
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If only it went back together and stayed together. Once it threw the blades, it didn't go back together worth a damn. It's very possible that some tiny wire springs popped out when it "barfed its blades." I've not be able to find a similar, three-bladed replacement but I keep looking. ); Thanks for your input.
-- Bobby G.
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Robert Green wrote:

been virtually untwisted. When John Blomstrand filed to patent the wire nut in 1950, that was his intent. If wires are straight and solid and of equal gage with even ends, I suppose the threads of a wire nut should engage every wire in a bundle of as many as six, mashing them together with no wiggle room.
Thirty years ago it was apparently common for electricians to use wire nuts badly, twisting wires together clockwise before twisting on the connector clockwise, then hoping tape would hold everything in place. I've redone many.
I love wire nuts even for conductors of dissimilar gages and stranded conductors, each of which may make it trickier to use wire nuts. Nearly 40 years ago, I installed a fairing on my motorcycle, which entailed splicing splicing the six stranded conductors of the fairing's wiring harness to six stranded conductors on my motorcycle. I used wire nuts. I've ridden more than 100,000 miles since then and never parked indoors, and those connections have never needed attention.
Pruning shrubs five years ago, I snipped the cord of my expensive headphones. The copper strands were too fine to solder, so I taped the three conductors with masking tape and used a wire nut to apply pressure and provide mechanical strength. Those phones still work fine.
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Me too. It's amazing how many bad ones I've come across where the twisting was bad or they didn't even use close to the right sized wire nut. My favorites, for 110VAC work, have little metal springs inside the nut. I prefer them without the metal inside for low voltage wiring, especially when I am not sure I am looking at the final configuration.

There's no doubt they can be done well in the hands of an experienced user. The problem is that in the hands of a beginner, they are usually not well done, and in my experience, bad wire nutting has caused many more problems than backstabbing. Bad nutting is also a lot harder to detect than someone failing to get most of the wire under a screw.

Hmm, I have a similar pair in the junk drawer that's also unsolderable. I think I might give your approach a try.
-- Bobby G.
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E Z Peaces wrote:

There are wire nuts and wing nuts and various designs in between. The important feature is the design of the spring. The wire nut had a round wire spring more suitable for stranded wire and the wing nut had a square wire spring wound with the edges out so it would cut into solid conductors making a better connection. The designs have morphed over the years with manufactures claiming suitability for both stranded and solid wires. I always look in the cavity of the connector before using it to see how it's made and/or if the darn spring is even there or corroded. Some of the wire/wing nuts have expansion room inside for the spring to expand which can make a better connection. I've grown fond of the newer push in connectors which I've had very good luck with.
http://tinyurl.com/nw5nt3
TDD
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