Safety of twist on wire connectors aka "wire nuts"

don_resqcapt19

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Staff member
Location
Illinois
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retired electrician

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
What does improper installation of a listed product have to do with it being listed? My comment did not say I have never seen a failed connection, it simply said I have never seen a wirenut that did not have a listing mark. That in no way addresses the ability of the installer to make a proper connection.
I fail to see improper installation or use with illustrated product failures.

Close-up photo's show no NRTL mark, label, or stamp on product shown.

There's no evidence this crap is listed. Any marks you described could be counterfeit sourced from Amazon.
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
This is what a valid product listing looks like from an on-line supplier

Not usually found, much less shipped with on-line knock offs

1.jpg
 

don_resqcapt19

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Staff member
Location
Illinois
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retired electrician
I fail to see improper installation or use with illustrated product failures.

Close-up photo's show no NRTL mark, label, or stamp on product shown.

There's no evidence this crap is listed. Any marks you described could be counterfeit sourced from Amazon.
The marks are on the ends of that type of product and I am 100% sure those are listed wire connectors. The marks are embossed into the ends and are difficult to see...in the purple one in you picture, you can see the embossing. Remember that for small listed parts like these, the only thing that is required to be on the product itself is the mark of the listing agency.
 
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rbalex

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Location
Mission Viejo, CA
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Professional Electrical Engineer
From the old UL Whitebook on "Marking":

When a UL Certified or Listed product is of such a size, shape, material or surface texture that, in UL’s opinion, it is impossible to apply legibly the complete marking to the product, the complete UL Listing Mark will appear on the smallest unit container in which the product is packaged. In these cases UL may authorize the use of the UL symbol on the product in addition to the complete UL Mark on the package.

In some cases, only the UL symbol will appear on the product; in others, only the packaging is marked to indicate "listing."

In any case, where FedOSHA or most State OSHAs have jurisdiction, the product must be listed/labeled if it can be - with or without a mark.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
I fail to see improper installation or use with illustrated product failures.
Don't many wire nut instruction say to twist the nut until the twist is reflected in one or two twists of the wire outside the nut? The pictures show the wires running straight out of the failed nut.

Cheers, Wayne
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Don't many wire nut instruction say to twist the nut until the twist is reflected in one or two twists of the wire outside the nut? The pictures show the wires running straight out of the failed nut.

Cheers, Wayne
At least one brand's instructions say that. Not sure if I have seen it on other brands.
 

retirede

Senior Member
Location
Illinois
The failures of the red ones pictured appear to indicate that the spring was conducting substantial current. The only way that’s possible is if one of the wires wasn’t stripped properly resulting in insufficient wire-to-wire contact. Maybe one of the wires isn’t stripped at all and the spring was able to cut through its insulation and make contact?
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
The failures of the red ones pictured appear to indicate that the spring was conducting substantial current. The only way that’s possible is if one of the wires wasn’t stripped properly resulting in insufficient wire-to-wire contact. Maybe one of the wires isn’t stripped at all and the spring was able to cut through its insulation and make contact?
They should have been twisted until the unstripped part started wrapping around themselves.
 

retirede

Senior Member
Location
Illinois
They should have been twisted until the unstripped part started wrapping around themselves.

Should have…. but regardless, the springs got extremely hot and I have no other expiation for that other than they were carrying current, which in a proper installation would not happen.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Should have…. but regardless, the springs got extremely hot and I have no other expiation for that other than they were carrying current,
Is it not plausible that the copper got very hot from a poor connection, and the springs just conducted that heat more effectively to the parts of the plastic which failed first?

Cheers, Wayne
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
Is it not plausible that the copper got very hot from a poor connection, and the springs just conducted that heat more effectively to the parts of the plastic which failed first?

Cheers, Wayne
I want to set up a workshop in my garage where I get to do stupid things and have them catch on fire or blow up.

Okay, I want to set up a work area in my driveway, far away from my house.

I think the question of what caused this particular failure is an interesting one, and I'd like to try and recreate various scenarios. That spring is going to carry the heat away from the bad connection, where ever it located.
 

kwired

Electron manager
Location
NE Nebraska
Don't many wire nut instruction say to twist the nut until the twist is reflected in one or two twists of the wire outside the nut? The pictures show the wires running straight out of the failed nut.

Cheers, Wayne
If that the case I been doing it wrong for a long time, at least on 12 and 10 AWG solid conductors. That requires a lot of torque and my fingers aren't going to deliver that anymore. One reason I been going more with push in and lever lock connections more recently. If you are supposed to need a tool to tighten properly then why not just go with set screw type terminal blocks?

It doesn't take that much force that you need superman strength to assure good enough connection for these smaller conductors.
 

retirede

Senior Member
Location
Illinois
Is it not plausible that the copper got very hot from a poor connection, and the springs just conducted that heat more effectively to the parts of the plastic which failed first?

Cheers, Wayne

I would have thought in that case, we’d see more evidence of thermal damage to the conductor insulation.
I think wirenuts are rated at 105C, which is higher than the 90C conductor insulation.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
I would have thought in that case, we’d see more evidence of thermal damage to the conductor insulation.
I think wirenuts are rated at 105C, which is higher than the 90C conductor insulation.
If you mean the conductor insulation that was never inside the wirenut (I don't think we can see any of that), that insulation is 5-10 times farther away from the spring in the damaged area than the damaged material of the wirenut. So I could imagine the temperature gradient being high enough that the exposed conductor insulation doesn't get damaged. But it's all speculation on my part.

Cheers, Wayne
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
In any case, where FedOSHA or most State OSHAs have jurisdiction, the product must be listed/labeled if it can be - with or without a mark.
20yrs ago aerospace contractors were easily faking NRTL markings for military connectors, today every major OEM from Ideal, Anderson, LEMO, MPT, & I-PEX, publish their own press releases warning about knock-offs.

Among public notices for fake markings on other products, UL reports multiple loses of holographic labels each year. The desire of law is not defacto, but reasonable people can identify some counterfeits.
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2017 NEC
Don't many wire nut instruction say to twist the nut until the twist is reflected in one or two twists of the wire outside the nut? The pictures show the wires running straight out of the failed nut.

Cheers, Wayne
If arcing is possible after a nicked conductor breaks inside the wire nut, arcing temperatures tend to destroy anything they touch.
 
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