new Edison Plugs

[ship]

So I was handed a new Edison plug today - didn’t go to LDI and while I remember seeing its news item, seeing it was important over dismissing it. Remember the plug to be locking and thought... here we go a locking Edison plug - as if taking it back to the days of the failing locks on stage pin plugs... - such a comment even caught the sales rep. off guard in having no idea of what I was talking about, but my boss completely understood. Yep, getting old given I remember such things, perhaps even against change while considering the below. Still young enough to consider switching to it.

Not sure about its worth and welcome other opinions about it.

It is a new product from Lex Products (someone else no doubt will post a link.) Edison plug (twistlock versions are on the way) that has a sort of spring locking lever connection to the conductors instead of screw terminal. Strip the wire as normal, insert it into the hole, than use your thumbs to close the latches and done on the wiring part. Normal two insert type two screw strain relief and cover on it to grip the cable as if a Leviton 115PR type residential grade rear of the plug. Servicable but not overly so designed for all types of cable.

Given this I was not totally sold in that if those on site don’t follow the general concept of strain relief or crushing the cable or strain relief, it doesn’t solve the problem of conductors now providing the strain relief. Rare argument as it were that a plug is not installed correctly but more common than it should be given those that don’t do proper wire strip lengths or proper strain relief tension. Outer jacket hanging half in or even outside the strain relief, partially stripped conductors inside the terminals with rubber now more under tension than conductors, etc. See it all the time thus my concern about the potential problems with such an above plug but in this case of posting for thoughts, not more so than problems with standard commercial grade plugs I already find problems with.

On the plus side, if Lex sold this product on the residential market such as to the home centers it would make a killing in market share as it is something that would sell well for a home owner, but for me to change my standards on tension - overcompensating for tension to allow for their marketed over tension or under tension due to strands of wire, I am not so sure. Fact is that as advertised, traveling about tends to settle individual conductors about within the plug to the point that they won’t have the original tension on them after some use and can at times become dangerously loose. Current flow expansion and contraction will also play a factor on this even more so as with resistance to the skin effect of wire given if a round surface were clamped, some of the strands of wire will be more under tension than other strands.

Their spring will other than that latter concept correct for most parts of tension problems in the spring - up until it wears out or reaches its maximum tension or has some form of metal fatigue compensate well for current flow expansion and contraction as with the sort of ultrasonic vibration effects use has on the strands of wire given a sufficient amount of them under tension. It will now however counteract that of some strands of conductor not as much under pressure than others. This as opposed to a more modern stage pin plug with all strands captured within a ferrule where no matter where the pressure comes from, all strands captured within the containment receive the same pressure - and also why you always want to use a ferrule or crimp terminal with modern stage pin plug. This given the screw terminal does not cut thru the ferrule and start cutting thru strands of wire - see latter argument above.

Overall, saw the above plug, yanked on the wire installed in it - the sales person noted that I was going to yank the wire out of the plug, and yep that was my intent. UL listed or not, I wanted to see how much tension that wire was under in accordance to what is sufficient for me or not. While it took a bit of effort to yank that single wire he had in the terminal out of the plug terminal, it didn’t take as much as I will have liked. This granted it was only one wire and with three it will have had much more pull out strength, I was concerned that were a strain relief not so well applied, or properly applied, or should inner conductors have the ability to move such as with a Euro style especially silicone heat wire cable, that strain relief short of crushing and cutting in will have been insufficient to withstand if not the first yanking of a plug by the cable, the second or third doing of it. Than you have a cable with conductors within the plug possibly shorting dangerously which will not as common to loose screw terminals rattling on a normal plug when loose, have no way of detecting. When a lose terminal on a normal plug, shake that plug and the terminals rattle. On this plug there would be no way to detect such a thing.

Anyway, it is a fascinating brilliant idea that would be a huge product for the home owner market but I am not so sure for the industry or my own use. Certainly at best training where I work is marginal and such plugs would provide sufficient engineering spec tension on the conductors of a cable - this especially for moving light fixtures I don’t much supervise it could work well the install on. Still some concerns, this even if for a 10% over normal plug price estimated.

So far I’m thinking that if training I give is sufficient it works, but doesn’t ensure anything. The proper spring tension would compensate for this. Just informed today that a bunch of L6-30 cables made recently fail the rattle test. Frequently a cable needs at least one good use before a final tension on it can be done but given new cable does not come back for final adjustment we over compensate instead in tension. That is good and bad. Good for the problems with conductors under current and shaking, bad for current flow. Also assuming that if initially over tightened, it will balance out and often that’s dependant upon who did the original tension.

Spring tension devices sound like a great idea, problems in concept for me and I am on the fence. For a school, it would be good and bad I expect. Good for getting it right, bad for education of the tension. For the industry... don’t know, lots of problems in general with any form of person putting on a plug.

After all of this, I am interested in what anyone else thinks.

[gafftaper]

I checked Lex's website and I see the locking Edison plugs listed (Nema L5-15) but there's no picture. Sorry.

[derekleffew]

As best I can tell, the device to which Ship is referring is not listed on Lex's site. All connectors listed here seem to be Leviton connectors. I used to buy only Bryant devices, easiest to built and lasted well, but now they are a part of Hubbell. I'm also a firm believer in the original being the best, I prefer Union Connector pin connectors over all others. I, too, suffered through the "Harj-Lock" craze--my favorite was that the tension on the male cord entry had to be less than the female entry, so that one wasn't left with dangling, bare, live wires. Not sure how other locking connectors deal with this issue.

Ship, have you seen Hubbell's SNAPConnect? Seems like it could be a labor savings for residential/commercial applications, but our industry doesn't use that many duplex outlets as a rule. Still, I suppose every second counts when one is paying $30+/hour, per electrician.

[Footer]

http://www.lexproducts.com/catalog/P...ts/lexloc.aspx

There ya go...

My opinion is it just takes a screw driver to get it right... do we really need this? You already have the tool in your hand to open the thing... And as far as tentioning goes, if you do it right once and with proper strain reliefe its really not an issue. I have a feeling that this thing would cause more harm then good.

[derekleffew]

Originally Posted by gafftaper

I checked Lex's website and I see the locking Edison plugs listed (Nema L5-15) but there's no picture. Sorry.

Gafftaper, the NEMA L5-15 is a 15A TwistLock™-type connector. The only locking straight blade (Edison) connectors I've ever seen use a level on the top of the connector above the blade slots and puts additional pressure on the blades once inserted, and they work only for the first two or three times, then loosen up and no longer lock. I've often thought someone would make use of the holes in the blades to make a locking plug/connector, but it hasn't happened yet.

Originally Posted by Footer4321

http://www.lexproducts.com/catalog/P...ts/lexloc.aspx

There ya go...

My opinion is it just takes a screw driver to get it right... do we really need this? You already have the tool in your hand to open the thing... And as far as tentioning goes, if you do it right once and with proper strain reliefe its really not an issue. I have a feeling that this thing would cause more harm then good.

Thanks, Footer4321, you've got better searching skills than Gafftaper and I have. While I like the concept of the Lex-Loc™, I suspect the plug/connector costs significantly more (Ship stated 10% more, but that came from a salesman) than a standard Hubbell/Bryant/Marinco device and the labor savings cannot offset the extra expense. Your point about needing a screwdriver to open the device is well taken, but a totally tool-less device would be against code, I'm sure. Only benefit would be as Ship said, insuring proper tension, but that remains to be proven.

[SteveB]

Looks like a solution lacking a problem.

Steve B.

[stantonsound]

Lex gave me a couple to try. We took them to the shop and put 12/3 soow cable in them, and gave them a try. The thing that we first noticed is that the clamping mechanism really doesn't save much time. There are already 5 screws to deal with (on the strain relief and to hold the plug in the housing), so does eliminating 3 more really help. With a battery powered screw driver, it is just as fast to screw it in.

Next, we hooked them up and did not tighten the strain relief, and then pulled on the SO cable, seeing how well the terminals held. We were able to pull the conductors out of the terminals with little problem.

They are about 15-20% more than the standard, so they are not too badly priced. All in all, not impressed.

[JD]

Don't like them. Of course, this comes from a guy who has a history of shearing the heads off of screws! Lets face it, the #1 causes of burned connectors in the 15-30 amp region is bad contact between the conductor and the plug. What I see in the spec sheet is a picture that has very little region of pressure contact. (Maybe a 32nd of an inch) The steel spring clip can not be counted on as a good conductor, so that leaves the area where the wire is in contact with the pin under pressure. Again, a very small area. We also know that even when new, conductors tend to have oxide on them, so the REAL contact area is even smaller! Give me a traditional screw anytime! Better yet, crimp, then solder (in that order only), then put it under the screw and add a split lock-washer!

[gafftaper]

That's all it is? I completely misunderstood. Is anyone worried about the 20 seconds it takes to screw down three terminals? I'm with Steve B. It's a solution without a problem.

[DarSax]

Exactly what I was thinking gafftaper. If you're converting plugs on an entire fixture inventory, then yea maybe the plug is helpful in minimizing rage. Still, I haven't the slightest idea why people would pay money for this.