Installing a Nema 14-50 on a 30 Amp Breaker

[Rocky_H]

I think the breaker will trip every time you try to charge.

Not necessarily. That's the thing that's a bit scary about this. The mobile charge cable would try to draw a steady 32A. Breakers are not digital. They have instant trip mechanisms if it is way over their threshold, and they have slower heat-based mechanisms if it's very close to their limit. If the circuit got 40 or 50 amps draw, it likely would trip right away. But 32 on a 30...hard to say. It might continue to run for a while, heating up the outlet and the wire and the breaker, before the breaker decided to trip, and I certainly wouldn't like that kind of scenario.

Why don't you just get the right wire for 50 amps and upgrade the breaker to the proper 50 amps?

But why bother, if they have a 30A circuit already run most of the way that is ready to use?

 

[RaeW]

You can’t put NEMA 14-50 receptacles on a 30A circuits! Not only that would be a code violation, but it would cause immediate problems when charging a Tesla! Here is why.
The type of the NEMA plug (adapter) you use with the UMC tells your car what’s the highest current the car is allowed to draw. If you use the 14-50 adapter, the car will assume you have a 50A rated circuit and will charge at a higher current than it’s supposed to! At best this will trip your circuit breaker, at worst, this can cause fire!

DO NOT DO IT!!!

No problem setting the car to charge at 24 amps. Once set, the car remembers this.

 

[brkaus]

No problem setting the car to charge at 24 amps. Once set, the car remembers this.

Until it doesn’t.

Someone on our local Tesla email list lost all settings during a firmware upgrade. They use a 20a outlet and a 3rd party converter. So their car one day started charging at 40a. Not good. I’d never recommend as a long term solution.

 

[RaeW]

Until it doesn’t.

Someone on our local Tesla email list lost all settings during a firmware upgrade. They use a 20a outlet and a 3rd party converter. So their car one day started charging at 40a. Not good. I’d never recommend as a long term solution.

Maybe something else involved (third part converter/firmware upgrade?) I have 14-50 outlet and use the TESLA charging cord. In 3.5 years it has never changed and there have been a lot of software upgrades. Obviously with a firmware upgrade one should think to reprogram.

 

[StellarRat]

No problem setting the car to charge at 24 amps. Once set, the car remembers this.

I don't think this is a safe solution.

 

[RaeW]

I don't think this is a safe solution.

Care to say why you believe this?

 

[brkaus]

Maybe something else involved (third part converter/firmware upgrade?) I have 14-50 outlet and use the TESLA charging cord. In 3.5 years it has never changed and there have been a lot of software upgrades. Obviously with a firmware upgrade one should think to reprogram.

Yes, homemade converter to allow the Tesla 14-50 to plug into a 20a outlet. That’s why they were relying on manually setting current lower.

Regarding the lost settings - I agree it was not typical. I agree something went wrong. Heck, maybe it was due to usb installed or something. But that something, even if 1 in 100000, why risk it when a ~$50 adapter can avoid the risk.

It could also happen if the gps location gets messed up.

- dear insurance agent - my house burned down because my Tesla was plugged in using a non-approved plug.

Doesn’t sound that great.

 

[Dutton]

I have a 240 v circuit fused for 20 amps. I use a NEMA 6-20 adapter that does not limit the amps rate. I have the car set to limit the amps rate to 16 amps (80% of the circuit breaker rating) and have had no trouble charging. I get 13 miles/hour and charge every night to 80% capacity. The only other place that I charge is at superchargers when I travel. The 16 amp rate restriction does not affect charging at superchargers and I believe that it is location dependent so if I charged with the same setup at a different location I would have to reenter the rate restriction.

I assume that your outlet is NEMA 6-30. If Tesla sells a NEMA 6-30 adaptor, that would be ideal. If they do not so you have to use a third party device, you need to limit the amps rate in the car to 24 amps (80% of the 30 amp circuit breaker rating).

 

[RaeW]

OK, interesting point. In my case the 14-50 outlet tells the car that it can charge up to 40 amps (not 32); however, for three and a half years the car has been set to charge 24 amps max (80% of 30 amp circuit breaker). Each time the car is plugged in the display shows the set limit of 24 amps and registers the amperage and voltage being received. Should this ever fail I would count on the 30 amp panel breaker to trip, so I see nothing unsafe about running 24 amps on the 30 amp circuit. This is far under the 40 amp maximum the car would recognize and far enough above 30 amps to trip the breaker.

 

[M3BlueGeorgia]

OK, interesting point. In my case the 14-50 outlet tells the car that it can charge up to 40 amps (not 32); however, for three and a half years the car has been set to charge 24 amps max (80% of 30 amp circuit breaker). Each time the car is plugged in the display shows the set limit of 24 amps and registers the amperage and voltage being received. Should this ever fail I would count on the 30 amp panel breaker to trip, so I see nothing unsafe about running 24 amps on the 30 amp circuit. This is far under the 40 amp maximum the car would recognize and far enough above 30 amps to trip the breaker.

So basically the car is protecting you from burning down your house. !!!!

Strongly suggest, given that you appear to have a 30A circuit, that you spend a very small amount of money to:
1) Change the socket from 14-50 to 14-30
2) Get the 14-30 adapter from Tesla

 

[brkaus]

OK, interesting point. In my case the 14-50 outlet tells the car that it can charge up to 40 amps (not 32); however, for three and a half years the car has been set to charge 24 amps max (80% of 30 amp circuit breaker). Each time the car is plugged in the display shows the set limit of 24 amps and registers the amperage and voltage being received. Should this ever fail I would count on the 30 amp panel breaker to trip, so I see nothing unsafe about running 24 amps on the 30 amp circuit. This is far under the 40 amp maximum the car would recognize and far enough above 30 amps to trip the breaker.

I agree with you and I have used such solutions on a short term basis. One in particular (relatives house I visit 2x yr) I use a 10-30 to 14-50 on an 50a extension cord.

But if the UMC would reach I’d buy the proper adapter. If I visited more I’d put in a proper plug or HPWC.

Still, I wouldn’t do every day or recommend to others or even my wife that is less electric experienced.

 

[RaeW]

So basically the car is protecting you from burning down your house. !!!!

Strongly suggest, given that you appear to have a 30A circuit, that you spend a very small amount of money to:
1) Change the socket from 14-50 to 14-30
2) Get the 14-30 adapter from Tesla

So then the car would recognize a max setting of 24/24 instead of 24/40? Since the car recognizes the 50 amp adapter at 40 amps, I assume it would then recognize 24 amps on a 30 amp socket. Since the car already has a set limit of 24 amps, what's the difference. What am I missing here?

 

[M3BlueGeorgia]

So then the car would recognize a max setting of 24/24 instead of 24/40? Since the car recognizes the 50 amp adapter at 40 amps, I assume it would then recognize 24 amps on a 30 amp socket. Since the car already has a set limit of 24 amps, what's the difference. What am I missing here?

Again, the car is recognizing there is something wrong with your electrical connection and scaling back the amps to 24 instead of 32.
Not a good scenario. Bad things could happen if some future OTA tweaks the algorithm, or a visitor plugs in a car without that level of protection. Your house insurance company could refuse to pay for the damages if cause by a deliberate code violation.

Best to proactively fix the issue. Sounds like just switching to valid socket and getting a different $35 adapter from Tesla, would be all that's required.

PS: You can never have too many adapters. In addition to the 5-15 and 14-50 which come as standard, I've added 5-20, 6-20 and 14-30.

 

[StellarRat]

Care to say why you believe this?

Because you never know when the car could get reset or something. Maybe a firmware change or someone messes with the screen. I just think you should use the right power circuit for the job, not a workaround.

 

[DriveMe]

Each time the car is plugged in the display shows the set limit of 24 amps and registers the amperage and voltage being received. Should this ever fail I would count on the 30 amp panel breaker to trip, so I see nothing unsafe about running 24 amps on the 30 amp circuit. This is far under the 40 amp maximum the car would recognize and far enough above 30 amps to trip the breaker.

So then the car would recognize a max setting of 24/24 instead of 24/40? Since the car recognizes the 50 amp adapter at 40 amps, I assume it would then recognize 24 amps on a 30 amp socket. Since the car already has a set limit of 24 amps, what's the difference. What am I missing here?

So you are willing to risk your house, all of your belongings, including your car, your life and the lives of everyone who lives with you, the lives of the firefighters who will be trying to save you, all that instead of spending less than a $100 to make it right?!!

You realize that neither your home insurance nor Tesla will ever cover any costs of such fire, since you violated the Code?!

 

[Vines]

Part of the reasons for standards and rules is so the next person can rely on things "just working"

While there are many things that can be made to work as temporary solutions, i am of the mind that permanent solutions should be made permanently safe. For instance, say you have someone watching your house while you go on a road trip, they also have an electric car and try to plug into your provided outlet.

Likewise if you sell the house and it doesn't get changed over to code compliant? There are many "What if" scenarios, and I agree that many of them are safe 999 out of 1000 times. However if we, as electric car trailblazers, don't do things right and to code, we are setting up the next generation for failure. Even one house fire per 1000 cars is too many.

As electric cars get more and more common there will be edge cases you didn't consider. You are out of town and the wife has someone over who wants to charge "Oh just use my husbands plug"

 

[RaeW]

For 3.5 years this system has been in place. The car will only accept 24 amps (by setting). If the setting fails for some reason, the car limits the draw to 40 amps which will easily trip a 30 amp breaker. I'm not worried and this has never happened.

 

[RaeW]

Part of the reasons for standards and rules is so the next person can rely on things "just working"

While there are many things that can be made to work as temporary solutions, i am of the mind that permanent solutions should be made permanently safe. For instance, say you have someone watching your house while you go on a road trip, they also have an electric car and try to plug into your provided outlet.

Likewise if you sell the house and it doesn't get changed over to code compliant? There are many "What if" scenarios, and I agree that many of them are safe 999 out of 1000 times. However if we, as electric car trailblazers, don't do things right and to code, we are setting up the next generation for failure. Even one house fire per 1000 cars is too many.

As electric cars get more and more common there will be edge cases you didn't consider. You are out of town and the wife has someone over who wants to charge "Oh just use my husbands plug"

 

[RaeW]

In my case there is a label on the outlet plate noting it is a 30 amp circuit. The TESLA cord is plugged into the outlet. I don't take the TESLA cord with me when I go out. The TESLA cord is a GFI. I am retired. I do not go away on trips and leave anybody at home. No one is going to plug in to my outlet (inside) other than me or my wife. In any event, this would be no different than someone plugging a device of any kind drawing more than 30 amps into a 30 amp circuit. Breakers are designed to protect the circuit. I am drawing 80% of the breaker rating as per code. Perhaps I am not being clear in the fact that the circuit is not being overloaded.

 

[davewill]

For 3.5 years this system has been in place. The car will only accept 24 amps (by setting). If the setting fails for some reason, the car limits the draw to 40 amps which will easily trip a 30 amp breaker. I'm not worried and this has never happened.

Sure, it CAN work fine. But you can't tell us that there isn't a possibility that the perfect storm of the car forgetting the setting and a faulty breaker could occur and cause a fire. Doesn't seem like it's worth saving a few bucks. Anyway, the main thing is that it would be irresponsible to recommend it to newbies asking for guidance here, even if it works for you.