L 14-50 EV receptacle

[LarryFine]

The issue isn't aluminum vs copper. It is ampacity and termination temperature. It is also whether or not the testing is adequate to test for continuous use. Don and Infinity are right in questioning if the test is really providing a real world use case for the application of EV charging.

And does the heating stem from the wire-to-terminal interface from or the contact-to-blade interface?

My first instinct says it's the latter; inadequate contact area and pressure for the continuous current.

What is physically different about the receptacles that don't overheat? Or do we need a new configuration?

 

[Elect117]

And does the heating stem from the wire-to-terminal interface from or the contact-to-blade interface?

My first instinct says it's the latter; inadequate contact area and pressure for the continuous current.

What is physically different about the receptacles that don't overheat? Or do we need a new configuration?

This is just my opinion. I don't work for a manufacturer nor have I take part in testing.

I believe it is the contact blades and the insulating materials. Cheaper plastics can melt slowly until eventual failure. It would be hard to tell by testing. Cheaper metal could cause a higher than expected temperature that the wire can handle but the plastics can not. There is also the possibility of the contact blades getting micro-scratches that negatively impact their ability to maintain good contact and eventually overheat/fail.

It could also be the chargers that plug into them. Like they are creating heat because those wires are sized to the minimum then the contact blades will of course get hotter and eventual failure occurs. Or partial connection where the charger is only partially inserted or where the charger's blades aren't the correct length, width, etc. to cover the surface area of the receptacle.

Lastly, the °C temp rating on the terminals where the branch circuit lands might not be straight forward and the average joe (homeowner, electrician, handyman, engineer, etc.) is using #8 when they should be using #6. That could create an issue with long term heating and cooling cycles but might not show up at the breaker since it is not exceeding the rating.

 

[LarryFine]

It could also be the chargers that plug into them. For example, if they are creating heat because those wires are sized to the minimum then the contact blades will of course get hotter and eventual failure occurs. Or partial connection where the charger is only partially inserted or where the charger's blades aren't the correct length, width, etc. to cover the surface area of the receptacle.

In my opinion, this pic I lifted from post #2 illustrates the main cause:

" . . . inadequate contact area and pressure for the continuous current."

 

[Elect117]

In my opinion, this pic I lifted from post #2 illustrates the main cause:

" . . . inadequate contact area and pressure for the continuous current."

View attachment 2574230

I agree. + cheaper plastics melting.

I also wonder if the mechanism that ensures the plates remain tightly closed against the charger (like a spring) are impacted by the heat and overtime are becoming way looser.

After I just spend the last 5 minutes looking at images on google after searching, "melted 50A receptacle" they all appear to the be Leviton, have one phase melted away, and have a bad contact area.

 

[BarryO]

Has anyone looked into the difference in physical construction of a L14-50 EV receptacle vs a standard one?

Thanks

I don't think there's any such thing as a NEMA L14-50 (locking) receptacle.

 

[marmathsen]

Here's one I got called out for in 2021. Someone had run this circuit with 6awg THHN about 100 ft to this receptacle. At the time I hadn't heard about receptacles melting so I just assumed it was an incorrectly torqued terminal. You can clearly see that the wire itself had melted through the plastic.

 

[infinity]

Leviton is now marketing a "heavy duty" 14-50. Has a cute little EV car symbol on its face.

It good to see that the industry is responding to this problem but it really annoys me that the testing standards for these devices are so poor that they actually burn up when used within their listing. Having said that this probably isn't the only product that has slipped past the poor practices of UL.

 

[gene6]

The issue isn't aluminum vs copper. It is ampacity and termination temperature.

Not to be argumentative or anything but if aluminum terminations are safe then I wonder why the new new heavy duty EV receptacles say 'copper wire only' ? And why would the rep say the issue was mostly with aluminum?

 

[gene6]

Here's one I got called out for in 2021. Someone had run this circuit with 6awg THHN about 100 ft to this receptacle. At the time I hadn't heard about receptacles melting so I just assumed it was an incorrectly torqued terminal. You can clearly see that the wire itself had melted through the plastic.

From here that looks like #8 Romex not THHN which would probably not have the same ampacity as THHN, I say romex and THHN are often easily confused in the 6 & 8 sizes and people whom don't do allot of residential probably don't realize #8 romex is only rated for something like 40 amps.

 

[infinity]

From here that looks like #8 Romex not THHN which would probably not have the same ampacity as THHN, I say romex and THHN are often easily confused in the 6 & 8 sizes and people whom don't do allot of residential probably don't realize #8 romex is only rated for something like 40 amps.

The NEC limits NM cable to the 60° rating in T310.16 but the conductors are still rated for 90° C so whether it's THHN in a raceway or NM cable there is no difference in the performance of the conductors. If the NM conductor will burn up then so will the THHN.

 

[BarryO]

The Hubbell is 75°C termination rated isn't it? I also remember the Hubbell being rated for continuous use at 50A. I believe the others are 60°C and are not rated for continuous use at 50A.

The cheap Leviton (this one) is stamped at 75C on the plate. Their newer HD one seems to be rated for 60C, maybe to force the use of larger gauge conductors?

279-S00

<p>Black - 50 Amp, 125/250 Volt, NEMA 14-50R, 3P, 4W, Flush Mtg Receptacle, Straight Blade, Grounding, Side Wired, Steel Strap</p>

leviton.com

 

[BarryO]

I have always used what I call a welder outlet, NEMA 6-50 receptacle for EV chargers (EVSE) that are not hard wired and not had any issue them.
I have yet to see a EV-charger (EVSE) that requires a neutral.

True, but the 14-50 plug seems commonplace on EVSE's, I suspect because 14-50 receptacles are commonplace (used for large RV's).

 

[gene6]

The NEC limits NM cable to the 60° rating in T310.16 but the conductors are still rated for 90° C so whether it's THHN in a raceway or NM cable there is no difference in the performance of the conductors. If the NM conductor will burn up then so will the THHN.

The conductors in post #26 look to me to be #8 Romex/ NM cable not THHN, which my understanding from this forum is that would affect the breaker on the branch circuit correct?

 

[wwhitney]

The conductors in post #26 look to me to be #8 Romex/ NM cable not THHN, which my understanding from this forum is that would affect the breaker on the branch circuit correct?

It's a regulatory difference, not a physics difference. So for identical installs with #8 Cu on a 50A breaker and a 75C rated receptacle, one THWN-2 and one NM, while the latter install is an NEC violation, it's no more likely to burn up at the receptacle in the manner under discussion.

Now if the receptacle is marked for 60C terminations only, that means that the thermal design was relying there being a #6 Cu conductor, so using #8 certainly could contribute to the problems depicted.

Cheers, Wayne

 

[marmathsen]

From here that looks like #8 Romex not THHN which would probably not have the same ampacity as THHN, I say romex and THHN are often easily confused in the 6 & 8 sizes and people whom don't do allot of residential probably don't realize #8 romex is only rated for something like 40 amps.

Yes you are correct. It is indeed NM, thanks for the correction. However I'm fairly certain it is indeed 6 AWG.

 

[infinity]

The conductors in post #26 look to me to be #8 Romex/ NM cable not THHN, which my understanding from this forum is that would affect the breaker on the branch circuit correct?

Yes NM cable may have a lower ampacity than THHN in a raceway but that wouldn't change anything regarding the function of the conductor.

 

[LarryFine]

The conductor capacity and the insulation temperature rating are two different, yet related things.

 

[retirede]

The cheap Leviton (this one) is stamped at 75C on the plate. Their newer HD one seems to be rated for 60C, maybe to force the use of larger gauge conductors?

279-S00

<p>Black - 50 Amp, 125/250 Volt, NEMA 14-50R, 3P, 4W, Flush Mtg Receptacle, Straight Blade, Grounding, Side Wired, Steel Strap</p>

leviton.com

I can’t find a temp rating for the terminations anywhere for the EV version.

It does have a -40 - +60C operating temperature range, but that should apply to the ambient temperature.

 

[retirede]

I don't think there's any such thing as a NEMA L14-50 (locking) receptacle.

I think the “L” in this context means “Leviton”. Note the space between the L and the 14-50 in the title.

 

[tortuga]

Now if the receptacle is marked for 60C terminations only, t

Its if the receptacle is marked 75C you can use the 75C, otherwise unmarked is 60C. [110.14 (C)]
Just wanted to point that out, as it can be confusing if you don't see any markings.
I think all the NEMA 6-50's I use are marked 75C.

What do you do when the male cord is part of the assembly?

Most seem to come with a 4 wire end.
Do you remove the male end and install a 3 wire cord end?

Yes if they come that way.
I typically just order them with a 6-50 to begin with,
my preference it to hardwire an EVSE so there is no 'receptacle' for other parts of the code to be concerned with.