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Can L6-20 charge at 32A?

Hey folks, new to EVs in general and this gorgeous Model 3 specifically. Thanks for the help here.

My garage has an L6-20 outlet that I'd like to use for charging (since my only other options are 5-15 normal US wall plugs).

I bought this adapter on AMZN to convert to a plug that I knew my kit has.

So when I plug into this adapter and my L6-20 outlet, the car shows 32A and ramps up to that. At this point, I'd expect the breaker to trip...since it's a 20A circuit as far as I understand, but it didn't. The breaker is a double 20A since it's 220V, but that doesn't allow it to flow 2x16A does it?

In any case, for now I dialed the car back to charge at 16A so I don't burn down the garage overnight, but I'd appreciate advice from someone who really knows this stuff well please! MVIMG_20180520_214050.jpg MVIMG_20180517_095026.jpg
 

FlatSix911

Porsche 918 Hybrid
Jun 15, 2015
7,472
7,689
Silicon Valley
Hey folks, new to EVs in general and this gorgeous Model 3 specifically. Thanks for the help here. My garage has an L6-20 outlet that I'd like to use for charging (since my only other options are 5-15 normal US wall plugs).

I bought this adapter on AMZN to convert to a plug that I knew my kit has.

So when I plug into this adapter and my L6-20 outlet, the car shows 32A and ramps up to that. At this point, I'd expect the breaker to trip...since it's a 20A circuit as far as I understand, but it didn't. The breaker is a double 20A since it's 220V, but that doesn't allow it to flow 2x16A does it? In any case, for now I dialed the car back to charge at 16A so I don't burn down the garage overnight, but I'd appreciate advice from someone who really knows this stuff well please!View attachment 302635 View attachment 302636

The adapter you purchased is a NEMA L6-20P to 14-50R... so the car thinks you are charging from a 32A continuous load circuit. :eek:
You should be sure to reduce the charge to 16A in the car and consider using 6-20R adapter rated for a 16A continuous load circuit.

Model S/X/3 Gen 2 NEMA Adapters
PDU Whips - Custom PDU Whips and Power Cords for Data Centers
https://www.amazon.com/NEMA-L6-20P-6-20R-Plug-Adapter/dp/B00DNDYIN6


 
Last edited:
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swaltner

Active Member
Oct 13, 2012
1,710
1,808
Kansas, USA
Consider getting the 6-20 adapter for the UMC and either replacing the outlet or use an adapter. And yes it should be limited to 16A.

THIS! Hopefully, you would just trip a circuit breaker, but it could be much worse to use your setup at 32 amps, which is twice what is safe to do.

I personally despise all the adapters that provide a socket that is rated for higher current than the plug. If you know how to use them, they can be used safely. If you’re not paying attention, they can be very unsafe to use.

Buying something like a L6-20 to 6-20 adapter, then plugging in the Tesla 6-20 adapter, would force you to the correct current rating for the outlet and wiring. Anyone could safely charge without being concerned about drawing too much current on the wiring and outlet. The two parts you need are:

https://www.amazon.com/dp/B07736C71R

6-20 adapter from Model S/X/3 Gen 2 NEMA Adapters

The confusion you had is why I don’t like the adapters like the one you purchased. These potentially unsafe adapters are not required when you use a proper adapter that doesn’t appear to provide more current than is safe to draw. Part of the problem was the Gen 1 mobile connector didn’t have a 6-20 adapter available, so people came up with these types of adapters that required you to manually turn down the current to safely charge the vehicle. These are not required any more, so I think we should stop using them.
 
I sent the Amazon seller the following question:

“Why are you selling such a dangerous device, that will allow a Tesla car to use 40 amps (NEMA 14-50) on a 20 amp rated plug?”

Please, get a proper 16/ 20 amp plug from Tesla. Tesla does not have any “L” series locking plugs, however you can buy a custom L6-20P to 6-20R adaptor from our company for $89 (Quick Charge Power). I’m sure there are others sources, as well.

Again, at a minimum, you will need to buy the correct NEMA 6-20 plug for your Mobile Connector (UMC).

Another option, in lieu of the adaptor, is to replace the wall receptacle with a NEMA 6-20R. That probably is probably only $10 at Home Depot.
 

TexasEV

Well-Known Member
Jun 5, 2013
7,652
8,918
Austin, TX
This was an example of someone not knowing what it is they didn’t know, and could have resulted in disaster. New owners, please do not use any third party adapters unless you’re certain you know what you are doing. And then post your plan here to get a second and third opinion to make sure it’s ok. Stay safe out there.
 
This was an example of someone not knowing what it is they didn’t know, and could have resulted in disaster....

Actually clearly I did have a notion that this was a 20-amp circuit and understand the 80% rule, since I set it to 16A...but I agree with your sentiment of approaching high amperage and adapters carefully.

Thank you for the responses; this confirmed what I was guessing, but a few inconsistencies remain....why didn't it go to 40A since it's a 14-50R...I would have expected that vs 32A (a multiple of 16 which made me wonder about the L6-20).

And why didn't the 32A rate trip my breaker???? Perhaps it hadn't actually ramped up above 20A yet to flip the breaker? (does anyone know if these ramp up more slowly than they actually report for safety reasons?). Otherwise I'll be checking that breaker more carefully.

Sadly I don't own this garage (rental) so I can't modify the plugs, but I really appreciate @swaltner for the suggestion of adapting adapters which will at least tell the charging unit what it's limits are. I'll consider going that route vs having to set the amperage limit and possibly having problems down the road.
 

TexasEV

Well-Known Member
Jun 5, 2013
7,652
8,918
Austin, TX
Thank you for the responses; this confirmed what I was guessing, but a few inconsistencies remain....why didn't it go to 40A since it's a 14-50R...I would have expected that vs 32A (a multiple of 16 which made me wonder about the L6-20).
The 14-50 adapter for the Gen 2 UMC only draws 32A. The14-50 adapter for Gen 1 UMC draws 40 A.
 
  • Informative
Reactions: Rocky_H
Actually clearly I did have a notion that this was a 20-amp circuit and understand the 80% rule, since I set it to 16A...but I agree with your sentiment of approaching high amperage and adapters carefully.

Thank you for the responses; this confirmed what I was guessing, but a few inconsistencies remain....why didn't it go to 40A since it's a 14-50R...I would have expected that vs 32A (a multiple of 16 which made me wonder about the L6-20).

And why didn't the 32A rate trip my breaker???? Perhaps it hadn't actually ramped up above 20A yet to flip the breaker? (does anyone know if these ramp up more slowly than they actually report for safety reasons?). Otherwise I'll be checking that breaker more carefully.

Sadly I don't own this garage (rental) so I can't modify the plugs, but I really appreciate @swaltner for the suggestion of adapting adapters which will at least tell the charging unit what it's limits are. I'll consider going that route vs having to set the amperage limit and possibly having problems down the road.

See my reply, yeah, that should bother you more than a bad adapter.
 
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I am genuinely shocked that breaker didn't trip. That should give you more alarm bells than the fact the false adapter didn't tell the UMC to reduce itself to 16A draw.

Oh absolutely! I was watching it ramp up slowly in amperage and expecting the familiar breaker sound from the panel on the other side of the garage, and it continued on up to 32A before I hit the "stop charging" button and scratched my head and smelled for a burning outlet. It's definitely something I'll mention to the landlord's handyman next time I see him with a big WTF in there.
 
Oh absolutely! I was watching it ramp up slowly in amperage and expecting the familiar breaker sound from the panel on the other side of the garage, and it continued on up to 32A before I hit the "stop charging" button and scratched my head and smelled for a burning outlet. It's definitely something I'll mention to the landlord's handyman next time I see him with a big WTF in there.

For sure, you might want to in the mean time "exercise" your breakers (turn them on and off and test them) as sometimes being held closed for so long can make them be "stuck", but what it's more of a sign of is a bad breaker. Also, you probably aren't going to smell burning right away, while it's more current than it's rated for, it can "still do it" for a period of time, a few seconds or so isn't really enough time for enough heat to get built up if it's just overloaded by several amps. Obv not ideal for any sort of significant period of time.

I wonder which breakers do you have?
This/how old those breakers are.
 
Oh absolutely! I was watching it ramp up slowly in amperage and expecting the familiar breaker sound from the panel on the other side of the garage, and it continued on up to 32A before I hit the "stop charging" button and scratched my head and smelled for a burning outlet. It's definitely something I'll mention to the landlord's handyman next time I see him with a big WTF in there.
Most breakers are designed to trip instantaneously only at fault level currents, otherwise you would have a lot of nuisance trips every time you start your vacuum cleaner with the coffee maker on. It sounds like you reacted quickly to the ramp, so I doubt it reached its designed trip time for that amount of current, and I definitely wouldn't expect it to trip as soon as it went above 20A.

See if you can find the model number and pull the time current curve for your breaker off the internet, then you can determine the amount of time it should take for your breaker to trip at 32A. I would expect somewhere around 30 seconds to a minute since 32A is less than twice the frame rating of the breaker.

Made-up trip characteristic example:
Breaker XYZ-30 will trip between 15-20 seconds at twice the frame rated current, but at three times the rated current, it will trip in 4-6 seconds. It will trip instantaneously above ten times the rated current.
 
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timk225

Active Member
Mar 24, 2016
2,082
2,392
Pittsburgh
How long was it drawing 32 amps for without tripping the breakers? I'd be worried about that.

You have 240 volts, not 220.

Zinsco and Federal Pacific breakers are crap and known for not tripping, those are GE breakers in your photo. My house has Cutler Hammer CH breakers (with the tan colored reset handle) and they are reputed to be very good.

I'd be calling your landlord and an electrician to check that breaker panel out. Post more photos and details about it.

I have my Model 3 charging from my 14-50 oven outlet on a 50 amp CH breaker. A Camco 15 foot 14-50 extension cord reaches it out the door to the car.
 
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