Do push-in connections actually overheat?

[RossS]

Having spent the better part of the afternoon trying to chase this down and basically getting nowhere, I thought I'd post this here.

There's a ton of opinion out there, and a whole lot of it is consistent with my own opinion that push-in type connections are not as electrically or mechanically sound as screw type, including wire nuts. But when I went looking for actual evidence, you know, like studies and such by groups that get paid to destroy stuff, I came up empty.

Can anyone point me to an actual study, preferably by a nationally recognized testing laboratory, of how well push-in type connections perform and whether they tend to overheat under higher load conditions?

 

[jim dungar]

Having spent the better part of the afternoon trying to chase this down and basically getting nowhere, I thought I'd post this here.

There's a ton of opinion out there, and a whole lot of it is consistent with my own opinion that push-in type connections are not as electrically or mechanically sound as screw type, including wire nuts. But when I went looking for actual evidence, you know, like studies and such by groups that get paid to destroy stuff, I came up empty.

Can anyone point me to an actual study, preferably by a nationally recognized testing laboratory, of how well push-in type connections perform and whether they tend to overheat under higher load conditions?

Are you looking at the stab type found on wiring devices or the spring style used in connectors?

 

[zbang]

Any connection will overheat if you drag enough current through it. A better question might be whether and how much they overheat under design spec conditions and heat/cool cycles.

 

[letgomywago]

Another factor to consider is also if the wire connection is listed then it faced destructive testing. Wago and Ideal products are fairly respected even with their push ins when in the past installer error and other issues causes some concern for some people

 

[mtnelect]

I didn't need an official study to convince me, (when I first came across this brilliant idea) that I suspect must have been approved by very respected authorities, that it would fail miserably. This idea encouraged using a device as a junction instead of "Pig-Tailing".

 

[LarryFine]

I didn't need an official study to convince me, (when I first came across this brilliant idea) that I suspect must have been approved by very respected authorities, that it would fail miserably. This idea encouraged using a device as a junction instead of "Pig-Tailing".

I have no problem with using screw or clamp terminals that way.

 

[mtnelect]

Every time I hear of labor-saving devices ... this reminds me of when I was an apprentice working on a housing development project and the foreman was complaining about a journeyman that was taking too much time installing the finish. Later, I heard that when homeowner(s) started moving in, they started complaining that nothing worked. None of the devices were wired.

 

[4x4dually]

I don't need any kind of study to tell me the connection is inferior to a screw or clamp no matter how they try to advertise it. Overheating comes from the current far exceeding the surface contact area. There is no comparison in the two connections. I whipped up this model because I'm better at pictures than explanations. How can anyone compare these two and tell me a push-in is as good as a screw or clamp? This of course may be slightly over exaggerating the push type connection, but it gets the point across.

 

[rambojoe]

Your picture has a code violation!

 

[kwired]

all connections can develop resistance. If the spring is good enough in a connection that relies on a spring to make contact, it in theory should be superior to a screw type connection that won't automatically tighten should there be thermal contraction of the conductor.

Other conditions can factor in to which is better overall though and each may have conditions where is better than the other method.

 

[Strathead]

I don't need any kind of study to tell me the connection is inferior to a screw or clamp no matter how they try to advertise it. Overheating comes from the current far exceeding the surface contact area. There is no comparison in the two connections. I whipped up this model because I'm better at pictures than explanations. How can anyone compare these two and tell me a push-in is as good as a screw or clamp? This of course may be slightly over exaggerating the push type connection, but it gets the point across.

View attachment 2571436

Better is subjective. Take your diagram. The Wago is better because a person with a IQ of 50 is more likely to be able to push the wire in far enough than he is to twist the wire around the screw the right way. (or, are you in a country with left hand threads) Is it that way south of the equator? (I hope you have a sense of humor)

 

[4x4dually]

Holy freggin' hell. Now I understand you all's posts. I did not take into consideration the way I wrapped the wire around the screw. My bad. The point was to show surface contact and I was trying to do it fast to get back to some other stuff. Opps. Bunch of jokers. LOL All good.

Dang it. It's too late to edit it above.

 

[garbo]

Here's my two cents. During my 50 years as a commercial electrician was never a fan of them. Argued with co workers back in the 1970's when they were using flimsy push in for both #12 & 14 wires. Told them when they come out with a push in for ground wire I might reconsider ( yes they finally have them ). I ran #2 copper THWN wires to two European machines that full load was 75 amps and had push in terminals for the feeders. I refused to use them and made the tech land them. Less then two weeks later two wires on one machine burnt up and second machine wires showed signs of overheating. On some terminal blocks found the control wires were sometimes difficult to remove. Appeared that screw terminals if properly used had less problems in damp or equipment that had shaking or vibration. On Danfoss drives you need a very small thin screwdriver to remove control wires. Most sparkies do not carry them.

 

[4x4dually]

Appeared that screw terminals if properly used had less problems in damp or equipment that had shaking or vibration.

An excellent point. Under shock or vibration the push-ins will continually cut into the soft copper until it snaps.....depending on the edge of the tab contacting the wire of course. I'm assuming they are sharp as to grab the wire. If that's the case, they will "saw."

 

[RossS]

Any connection will overheat if you drag enough current through it. A better question might be whether and how much they overheat under design spec conditions and heat/cool cycles.

Or an even better question is how and by whom have the devices been tested and what are the test results? I can't very well argue either side to NAVFAC by saying a bunch of electrical people say they're fine - or not fine, depending on whose opinion you get.

 

[RossS]

Are you looking at the stab type found on wiring devices or the spring style used in connectors?

Stab type for sure; if by spring type you mean wire nuts, no, not looking for those. And I couldn't find engineering type drawings/diagrams of the different types of WAGOs. I assume the push-in are just like stab type, but I'm not sure about the lever type. Those look like they might have a whole lot more metal-to-metal contact area.

 

[RossS]

I didn't need an official study to convince me, (when I first came across this brilliant idea) that I suspect must have been approved by very respected authorities, that it would fail miserably. This idea encouraged using a device as a junction instead of "Pig-Tailing".

I'm not trying to convince myself. UFC/UFGS are silent on the matter; I need defensible research, if I want to include them in my specs.

 

[RossS]

I don't need any kind of study to tell me the connection is inferior to a screw or clamp no matter how they try to advertise it. Overheating comes from the current far exceeding the surface contact area. There is no comparison in the two connections. I whipped up this model because I'm better at pictures than explanations. How can anyone compare these two and tell me a push-in is as good as a screw or clamp? This of course may be slightly over exaggerating the push type connection, but it gets the point across.

View attachment 2571436

I don't think your picture exaggerates the push type at all (although for the screw type I'd turn the hook the other way).

 

[RossS]

Holy freggin' hell. Now I understand you all's posts. I did not take into consideration the way I wrapped the wire around the screw. My bad. The point was to show surface contact and I was trying to do it fast to get back to some other stuff. Opps. Bunch of jokers. LOL All good.

Dang it. It's too late to edit it above.

View attachment 2571439

Sorry, I should have scanned all the replies before I commented. Oh well, it's not the first time I've done that, probably won't be the last either.

 

[RossS]

Better is subjective. Take your diagram. The Wago is better because a person with a IQ of 50 is more likely to be able to push the wire in far enough than he is to twist the wire around the screw the right way. (or, are you in a country with left hand threads) Is it that way south of the equator? (I hope you have a sense of humor)

I'm thinking a person with an IQ of 50 probably shouldn't be working with electricity.