Think I dodged an electrical fire

[DiamondHands]

Hi friends, my new construction home was fitted with a NEMA 14-50 Outlet by a certified electrician about four months ago. Around the same time, I had purchased a charging cable from the Tesla website.


Fast forward to last night, when I walked in my garage and noticed a distinct burning smell, but I did not see any smoke. I immediately turned my attention to the charging cable connected to our model X, and saw that the smell was strongest there, and I also saw some grey discoloration on the outlet receptacle itself. I immediately killed the power in my breaker box, after which I disconnected the cable from the model X. Have a look at the photos. Any thoughts? I of course have an electrician coming out sometime to today.

 

[mspohr]

Unfortunately, there are appear to be a lot of cheap 14-50 sockets (even those installed by qualified electricians).
Looks like you have a defective socket. The electrician should replace it and make sure he uses a good quality socket.
The plug may be damaged also. It might be able to be cleaned up but it might need to be replaced.

 

[electracity]

Tell the electrician you want a Hubbell part # HBL9450A or Cooper part #5754N as recommended by Tesla. Also contact Tesla because you can't be sure its the outlet or in-wall wiring.

 

[jdw]

PSA - periodically replace your NEMA 14-50 outlet

 

[ai4px]

I can't help but notice the same pin (right hand pin) is the one damaged in OP's photo and in the PSA linked article. Hmmm...

 

[electracity]

PSA - periodically replace your NEMA 14-50 outlet

The $50 plugs speced by Tesla shouldn't normally need to be replaced. The Tesla spec deliberately doesn't mention the common $10 Leviton "Industrial Grade" 14-50 sold at home depot. If a Tesla EE takes the time a spec for an plug use that plug.

 

[Joe F]

I second the Hubbell HBL9450A recommendation. About $100.00 on-line including tax and S&H.

19 months old and no signs of overheating, charging at 40A. Note though I never unplug the UMC except for serious lightning storms.

 

[Saghost]

I can't help but notice the same pin (right hand pin) is the one damaged in OP's photo and in the PSA linked article. Hmmm...

Only two pins get loaded when a Tesla is charging from a 14-50, the two hot lines, which I believe are the left and right side pins, so you had a 50% chance...

 

[bro1999]

PSA - periodically replace your NEMA 14-50 outlet

So I read that whole thread. Seems to me that crappy installation of a 14-50 outlet was the culprit, and not repeated plugging-unplugging? Though repeated plugging/unplugging may have sped up the failure out the outlet due to crappy installation.

Assuming a 14-50 is properly installed, there shouldn't be an issue in the long term unplugging/plugging several times a year?
If repeated plugging/unplugging is not recommended, would buying an extra 14-50 adapter and leaving it plugged it at all times be the "best" way to preserve outlet integrity?

 

[DiamondHands]

Morning all, I really appreciate the input, many thanks!

 

[Lloyd]

You may find that one of the lugs was not properly torqued.

 

[bpjod]

On a somewhat related note, the NEMA 5-15 outlet that our Volt has been plugged into was starting to look like that after a little more than a year of charging our Volt. When the electrician came to install our HPWC we had him look at the outlet for the Volt and he decided to put in a dedicated circuit with a commercial grade NEMA 5-20 outlet for our Volt. It seems to me there might be a number of low quality receptacles out there that aren't up to the demands of high current for a long period of time such as what plug-in cars require. Maybe it's time for the regulators to revisit the standards before there are fires.

 

[posity]

I have been designing high current machinery for years. Some up to 4000A. I suspect EV owners are going to be reporting a LOT of these types of failures. And from pictures like this, we'll be seeing fires reported by EV owners. Electricians will slowly learn which products have high failure rates - very similar to the whole Federal Pacific (FPE) panels debacle. For example, there are still professional electricians out there that will see an FPE panel and fail to advise their prospective customers of the incredible fire hazard, presumably because they just don't have the experience. Even after 30+ years of thousands of reported FPE fires and a breaker failure rate upwards of 30%.

So it is up to us EV owners to insist our electricians use the brands of devices that work reliably for the application. Since EVs are new to most electricians, you are going to find a lot of electricians giving advice based on little to no experience, which equals bad advice in this case. EV's are a case where the brand of receptacle really does matter IMHO. If wiring your range, not so much.

14-50 receptacles have been designed for very low insertion cycle counts (50 is the typical specification) for use on ranges - which are a purely resistive load at the high currents. With EVs, we now have complex impedance loads and so the quality of the receptacle gets to be much more important to avoid failures. An EV receptacle is just a significantly different application than a range - due to the insertion counts and complex impedance load.

Bottom line is I completely agree with Tesla's suggestion that people wire their EV receptacles using Hubbel brand. This is another example of Tesla's engineers knowing what they are talking about, and getting the details right. I have multiple customers that have gone to specifying ONLY Hubbel brand connectors on their equipment due to the frequent failures of using other brands. Hubbell is expensive, but this is a case where you are getting what you pay for. You won't go wrong with Hubbell, other than the initial dent in your pocketbook.

One last thing: BE SURE to replace both the plug and receptacle since the Tesla plug was damaged by the failed receptacle. Do NOT try to clean up and re-use the plug: I have personally seen high current plugs re-used in plants many times, with close to zero success rate. Buy both a new Hubbell receptacle and new Tesla 14-50 Mobile Connector adapter cord.

 

[DiamondHands]

I have been designing high current machinery for years. Some up to 4000A. I suspect EV owners are going to be reporting a LOT of these types of failures. And from pictures like this, we'll be seeing fires reported by EV owners. Electricians will slowly learn which products have high failure rates - very similar to the whole Federal Pacific (FPE) panels debacle. For example, there are still professional electricians out there that will see an FPE panel and fail to advise their prospective customers of the incredible fire hazard, presumably because they just don't have the experience. Even after 30+ years of thousands of reported FPE fires and a breaker failure rate upwards of 30%.

So it is up to us EV owners to insist our electricians use the brands of devices that work reliably for the application. Since EVs are new to most electricians, you are going to find a lot of electricians giving advice based on little to no experience, which equals bad advice in this case. EV's are a case where the brand of receptacle really does matter IMHO. If wiring your range, not so much.

14-50 receptacles have been designed for very low insertion cycle counts (50 is the typical specification) for use on ranges - which are a purely resistive load at the high currents. With EVs, we now have complex impedance loads and so the quality of the receptacle gets to be much more important to avoid failures. An EV receptacle is just a significantly different application than a range - due to the insertion counts and complex impedance load.

Bottom line is I completely agree with Tesla's suggestion that people wire their EV receptacles using Hubbel brand. This is another example of Tesla's engineers knowing what they are talking about, and getting the details right. I have multiple customers that have gone to specifying ONLY Hubbel brand connectors on their equipment due to the frequent failures of using other brands. Hubbell is expensive, but this is a case where you are getting what you pay for. You won't go wrong with Hubbell, other than the initial dent in your pocketbook.

One last thing: BE SURE to replace both the plug and receptacle since the Tesla plug was damaged by the failed receptacle. Do NOT try to clean up and re-use the plug: I have personally seen high current plugs re-used in plants many times, with close to zero success rate. Buy both a new Hubbell receptacle and new Tesla 14-50 Mobile Connector adapter cord.

Hi, thanks much for taking time to reply- much appreciated.

 

[bro1999]

So took these temps 30 minutes after plugging my Bolt in. Ambient temperature in the garage was 90F. Considering that, do these temps look fine?

 

[Saghost]

So took these temps 30 minutes after plugging my Bolt in. Ambient temperature in the garage was 90F. Considering that, do these temps look fine?
View attachment 316053View attachment 316056 View attachment 316057 View attachment 316058 View attachment 316059View attachment 316060

I don't see anything to be concerned about in those temperatures in a 90F room.. Hopefully after 30 minutes you're getting close to a steady state temperature.

 

[gilscales]

Hi friends, my new construction home was fitted with a NEMA 14-50 Outlet by a certified electrician about four months ago. Around the same time, I had purchased a charging cable from the Tesla website.


Fast forward to last night, when I walked in my garage and noticed a distinct burning smell, but I did not see any smoke. I immediately turned my attention to the charging cable connected to our model X, and saw that the smell was strongest there, and I also saw some grey discoloration on the outlet receptacle itself. I immediately killed the power in my breaker box, after which I disconnected the cable from the model X. Have a look at the photos. Any thoughts? I of course have an electrician coming out sometime to today.

View attachment 315683 View attachment 315684

I would like to know if you determined what the failure was caused by? sometimes this is a problem with installation (insulation trapped under screw terminals, terminals not tightened enough) and sometimes it is caused by loose tension on the contact blades in the outlet itself, curious if you had found out which one is the problem?

 

[Rocky_H]

I just checked and my hunch was correct. From the gold pins, that is the Tesla "Corded Mobile Connector".
Model S/X Corded Mobile Connector

It is not the UMC (Universal Mobile Connector) that the cars come with, which have silver colored pins. The difference is that the Corded Mobile Connector, with the permanent molded on 14-50 plug is based on the older UMC and draws 40A continuous versus the 32A continuous capacity of the newer UMCs.

You said this was an outlet in a new house construction. So, I am wondering if this 14-50 outlet you had was on a 40A breaker and smaller wiring than if it were actually built to be a 50A circuit.

 

[DiamondHands]

I would like to know if you determined what the failure was caused by? sometimes this is a problem with installation (insulation trapped under screw terminals, terminals not tightened enough) and sometimes it is caused by loose tension on the contact blades in the outlet itself, curious if you had found out which one is the problem?

Hey there. I was told that the terminals likely weren’t tight enough.

 

[gilscales]

Hey there. I was told that the terminals likely weren’t tight enough.

Unless you have already replaced your receptacle with a Hubbell or Bryant then I would read post #62 in this thread Burnt nema 14-50 plug and breaker tripped as it will show you just why these are the only outlets one should use for a high amp constant draw appliance like an EV charger.