NEMA 14-50 Plug Meltdown / Near Fire

[mswlogo]

Did you get the work inspected by the city for a permit after the install?

Inspectors don't (usually) check if screws are tight but they might spot check something closely if they don't know you.

If you follow the general rules like metal housings, wire sizing, breaker sizing etc. the whole idea is your house shouldn't burn down if there is a fault. Because *sugar* does happen.

 

[nwdiver]

Yes.

I have 2 melted v1 UMCs and a very not melted $10 6 year old 14-50 socket that disagree

 

[N54TT]

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My main house breaker tripped tonight. Upon investigating, I saw black smoke curling up my garage wall and smelled burning plastic, from where my 14-50 plug is located. Turns out my electrician had installed the plug with a loose black conductor, causing the outlet and plug to meltdown. At this point I am much more relieved than upset because I was able to stop what could have been a disaster. I will be double-checking every connection myself going forward in the install of a HPWC to replace the 14-50! If you smell burning plastic, investigate!

Do you routinely unplug the 14-50...or has it remain plugged in since it was installed? There has been reports that if you constantly unplug and plug...it wears down the outlet...contacts get loose and excess heat is generated. This is especially the case with non commercial grade Leviton outlet that you can get at HD.

 

[Jaywlker]

Curious OP were you ever seeing any of the status lights indicating a problem?

Never had any light indicators that suggested any problem. Dialing down
the amperage is a great idea. Agree.

 

[Jaywlker]

Do you routinely unplug the 14-50...or has it remain plugged in since it was installed? There has been reports that if you constantly unplug and plug...it wears down the outlet...contacts get loose and excess heat is generated. This is especially the case with non commercial grade Leviton outlet that you can get at HD.

Plug was never removed from the receptacle.

 

[eprosenx]

Inspectors don't (usually) check if screws are tight but they might spot check something closely if they don't know you.

If you follow the general rules like metal housings, wire sizing, breaker sizing etc. the whole idea is your house shouldn't burn down if there is a fault. Because *sugar* does happen.

Yeah, I have *never EVER* seen an inspector check an actual connection. They are generally just glancing at wire sizes, types, etc... They don't generally check the quality of the actual work.

When I had my Wall Connector installed the inspector showed up without notice and so I did not have time to take the panel cover off for him. He took one glance at my EMT bending job and commented on how amazing it was that I did it all in one piece (no stitching together multiple pieces even though it needed seven bends) and just signed off the project. <shrug> Don't rely on the inspectors. ;-)

 

[Feathermerchan]

Have a look at that definitive thread. The Hubble has a totally different king of connection mechanism. It has a sliding metal block between the end of the screw and the wire. The Leviton just has a screw contacting the wire directly.
FWIW you can save some time, money and energy by installing a 6-50. It saves one 6 ga conductor (there's no neutral) and makes wiring in the panel and at the plug much easier.
I have a gen 1 UMC so I can leave it plugged in. I take the 32A Gen 2 with me.

 

[lolder]

10 months ago I installed my 14-50 a foot from the panel with #6 wires in a conduit. It was hard to tighten the wires to the receptacle. The box was always warm but the whole UMC-2 and cable are warm also. About a month ago the UMC-2 ramped down to 12 a from 32 and the box was much warmer. I took the 14-50 apart and got another 1/2 turn on the screws. The box is now cool all the time. your 14-50 should not be warm. I also installed two networked smoke alarms in the garage and bedroom for about $70.

 

[eprosenx]

10 months ago I installed my 14-50 a foot from the panel with #6 wires in a conduit. It was hard to tighten the wires to the receptacle. The box was always warm but the whole UMC-2 and cable are warm also. About a month ago the UMC-2 ramped down to 12 a from 32 and the box was much warmer. I took the 14-50 apart and got another 1/2 turn on the screws. The box is now cool all the time. your 14-50 should not be warm. I also installed two networked smoke alarms in the garage and bedroom for about $70.

Any chance you caught some insulation in the screw/clamp terminals? That would cause what you describe too. Perhaps the final tightening after it melted off made better contact?

This stuff is no joke! Always make sure your connections are properly torqued!

FWIW, 32a through a UMC 2 on a 50a circuit, the receptacle and wire should be cool. 40a on a UMC 1 on the same circuit would probably be acceptable to be a little bit warm. The UMC 2 itself and its wire being a little warm I suspect is also fine since it is built to be the minimum thickness that is safe (to save on weight/size and cost). Some degree of warm is OK and EXPECTED in properly sized electrical systems. Hot is not OK though... (and warm is not ok when you are nowhere near the limit of the circuit/wire in question)

 

[Rottenapplr]

10 months ago I installed my 14-50 a foot from the panel with #6 wires in a conduit. It was hard to tighten the wires to the receptacle. The box was always warm but the whole UMC-2 and cable are warm also. About a month ago the UMC-2 ramped down to 12 a from 32 and the box was much warmer. I took the 14-50 apart and got another 1/2 turn on the screws. The box is now cool all the time. your 14-50 should not be warm. I also installed two networked smoke alarms in the garage and bedroom for about $70.

Ya I put a nest thermostat next in the garage. Just because sugar happens.

 

[Jaywlker]

Do you routinely unplug the 14-50...or has it remain plugged in since it was installed? There has been reports that if you constantly unplug and plug...it wears down the outlet...contacts get loose and excess heat is generated. This is especially the case with non commercial grade Leviton outlet that you can get at HD.

10 months ago I installed my 14-50 a foot from the panel with #6 wires in a conduit. It was hard to tighten the wires to the receptacle. The box was always warm but the whole UMC-2 and cable are warm also. About a month ago the UMC-2 ramped down to 12 a from 32 and the box was much warmer. I took the 14-50 apart and got another 1/2 turn on the screws. The box is now cool all the time. your 14-50 should not be warm. I also installed two networked smoke alarms in the garage and bedroom for about $70.

All excellent ideas / ways to properly address safety!

 

[N54TT]

I also have a networked fire/smoke/heat alarm in the garage. It’s connected to my alarm system so it’s always being monitored.

 

[Saibot]

I've put in several of the Leviton's and noticed that the wire tends to mash under the repositioning of the wire, such as bending it to fit inside the junction box, and needs torqued down again. That being said, once it's been mashed down properly again, it is good to go. I've never had any noticeable heat emanating from the plug.

And for what it's worth, my panel/electrical work vs. the work I've paid for is certainly not the same. I'm in no hurry and very diligent on safety, inspection, etc. I can't say the same for the 4 or 5 electricians I've used on the past. So just to throw my 2 cents in to this conversation, I think this is more about careless work than a specific product's connection terminals (although it may allow for such bad connections to more easily occur).

Thanks for sharing your experience so the community learns and avoids the same pitfalls!

 

[lolder]

No, I didn't have any insulation under the screw but I was aware of the problem because the #6 wire is very stiff and closing up the box is like trying to get 10 lbs. into a 5 lb. bag. The terminals were not really loose and it took a fair amount of torque to get another 1/2 turn. The UMC-2 plug, cables and housing are still warm but the box is not. The 50 a breaker is slightly warm ( as is my house AC breaker) and the conduit is slightly warm. I think that is normal. I have 245-250 vac before it amps up and about 3 v less at 32 a. Some of it at the service entry. I had a surge protector installed at the meter by the power company before I got the car and they sprayed all the meter terminals and my not yet plugged in 50 A breaker with their contact cleaner.

 

[jdcollins5]

One recommendation I would make - after a month or so of service, go back and re-check the terminal connection tightness at the plug and breaker ends. After several charging thermal cycles, I was able to make about a 1/4 turn on all connections.

 

[Togg]

I'm not a licensed electrician, but I have read most of the electrical code.

1) Electrical interior box minimum size in cubic inches is also very important. There are code rules for minimum size, but it's often overlooked. When there isn't enough room in the box the insulation on the heavy wires are over-stressed as the wires are installed as they're bent into position. This also overstresses the connector to wire junction at the same time. I generally try to oversize the box as I find it works better most of the time.

2) Also at least here in California, if a fire burns your house down and the cause is tied to incorrect wiring practices of the electrician, the electrician can be held fully financially responsible. The rule is if a contractor burns your house down you pretty much have a right to their house and their assets. Contractors can also purchase insurance to help protect them. All of the electrician's private assets are at risk. Sooooo.. Contractors doing electrical work on other people's homes need to be really careful.

 

[murphyS90D]

Stranded wire should have a copper ferrule crimped on it before it is inserted in to the outlet. Then the screw should be torqued to the specification with a torque wrench. This guarantees that no wire strands get missed in the clamping process. One missed strand will result in heat generation. Heat generation over time will make the connection worse until it eventually goes into thermal runaway.

 

[MSAGRO]

View attachment 416954 View attachment 416958 View attachment 416959

My main house breaker tripped tonight. Upon investigating, I saw black smoke curling up my garage wall and smelled burning plastic, from where my 14-50 plug is located. Turns out my electrician had installed the plug with a loose black conductor, causing the outlet and plug to meltdown. At this point I am much more relieved than upset because I was able to stop what could have been a disaster. I will be double-checking every connection myself going forward in the install of a HPWC to replace the 14-50! If you smell burning plastic, investigate!

I have the first GEN Tesla charger,when I had it professionally wired in,

they put in a 60 amp breaker. Is that a good one to have, or should I reduce it?

 

[JoelDi]

I had the same problem about nine months ago. I believe my outlet was a Leviton as well, purchased at Lowe's. I replaced it with another brand from an electrical supply house that seemed heavier. I absolutely torqued the screws down well. I really need to open up the one I have now and retighten them again. I did it once about a week after I put it in.

 

[eprosenx]

Stranded wire should have a copper ferrule crimped on it before it is inserted in to the outlet. Then the screw should be torqued to the specification with a torque wrench. This guarantees that no wire strands get missed in the clamping process. One missed strand will result in heat generation. Heat generation over time will make the connection worse until it eventually goes into thermal runaway.

I am unaware of anywhere in code in the US that requires ferules. They are popular in other countries (Europe) I think, but no requirement here. Probably a good idea though (the Tesla Wall Connector specifically recommends them, but honestly, in the US I have never ever seen an electrician use them).

I am not sure that a single missed strand is such a dire situation, but I always avoid it for sure. If it is missed I would expect it simply to not be a a part of the current path as it would not be connected to anything. If it is shorted to something else that would likely cause a ground or phase to phase fault and some breaker or GFCI might blow, or the strand would vaporize. Are you perhaps suggesting that a single strand not properly connected, but still touching would generate heat? I would just think the bulk of the current would flow over the rest of the properly connected wire. (i.e. I am wondering if a single missed strand is that much of a serious deal - but clearly you never want wire strands missed)

I do totally agree that properly torquing connections is most critical! (though I personally have never seen electricians actually use torque screwdrivers, lol...)