Installing a Nema 14-50 on a 30 Amp Breaker

[wcorey]

I am a pretty smart guy, but a moron when it comes to electricity. I have been following this thread and my head spins. I didn't know if I should start my own thread because my question is a little different, but I'll try here.

I am having an electrician run a 240v line from my breaker to the garage where I will put in a NEMA 14-50 outlet. I haven't decided on whether I'll get the SR+ or the LR. I can see that I have a 30 and a 20 amp free on my breaker next to each other. Would I be ok with 50 amps if I were going to get the LR model 3 or do I need 60 as recommended by Tesla? Or is that just if I were using their Wall Charger? If I use 50, does that just mean that I will get a slower charge on the LR or is there a chance for all the bad things I read here?

Remember, I'm a moron, I might not understand if you belittle me for not understanding.

I am an Extra Class Ham Radio licensee. I can tell you how to build an oscillator, band pass filters, band eliminate filters, construct high gain antennas but wire a service panel? NADA. There is a good friend of mine in La Jolla CA who convinced me about a year ago to future proof your big projects. If you are starting from scratch, my advice, have him (or her) run a line from your main service panel to your garage that can take 100a 240v. Buy a Tesla Charger and guard that line to the garage with a 60a circuit breaker. Then wire the Tesla Charger for a 60a (48a continuous) feed. Your car will charge at 48a. You may not need it now but should you later, the heavy lifting is already done.

I'd have to go back and re-read comments made to me in this thread but even with 50a into a 14-50, a Model 3 will only charge at 32a. It's a bit above your comment.

@LCR1 told me
"No you couldn't because the 14-50 is still rated at 40amps max continuous load. You'd also need the wall charger to get 48A, the mobile one won't do it. The only way to get 48A is the wall charger directly wired to a 60Amp breaker".

 

[garth_angst]

I am an Extra Class Ham Radio licensee. I can tell you how to build an oscillator, band pass filters, band eliminate filters, construct high gain antennas but wire a service panel? NADA. There is a good friend of mine in La Jolla CA who convinced me about a year ago to future proof your big projects. If you are starting from scratch, my advice, have him (or her) run a line from your main service panel to your garage that can take 100a 240v. Buy a Tesla Charger and guard that line to the garage with a 60a circuit breaker. Then wire the Tesla Charger for a 60a (48a continuous) feed. Your car will charge at 48a. You may not need it now but should you later, the heavy lifting is already done.

I'd have to go back and re-read comments made to me in this thread but even with 50a into a 14-50, a Model 3 will only charge at 32a. It's a bit above your comment.

@LCR1 told me
"No you couldn't because the 14-50 is still rated at 40amps max continuous load. You'd also need the wall charger to get 48A, the mobile one won't do it. The only way to get 48A is the wall charger directly wired to a 60Amp breaker".

I want to save the $500 and not get the Wall Charger. I am perfectly fine with the included plug not taking full advantage and only charging at 32a. Will the onboard charger on the LR though try to get 48a? All I really want to know is that it is safe to have the LR model use the 14-50 on the 50a breaker or do I need a 60a breaker?

 

[Petrlol]

I want to save the $500 and not get the Wall Charger. I am perfectly fine with the included plug not taking full advantage and only charging at 32a. Will the onboard charger on the LR though try to get 48a? All I really want to know is that it is safe to have the LR model use the 14-50 on the 50a breaker or do I need a 60a breaker?

The included charger with the 14-50 will limit itself to 32 amp. If you're putting in a 14-50 plug put it on a 50amp breaker with 6awg wire.

This will give you a code compliant 14-50 that can be used for a RV or whatever a future owner wants to use it for.

 

[garth_angst]

The included charger with the 14-50 will limit itself to 32 amp. If you're putting in a 14-50 plug put it on a 50amp breaker with 6awg wire.

This will give you a code compliant 14-50 that can be used for a RV or whatever a future owner wants to use it for.

Great, that is the answer I was looking for. Thank you.

 

[Alketi]

I am a pretty smart guy, but a moron when it comes to electricity. I have been following this thread and my head spins. I didn't know if I should start my own thread because my question is a little different, but I'll try here.

I am having an electrician run a 240v line from my breaker to the garage where I will put in a NEMA 14-50 outlet. I haven't decided on whether I'll get the SR+ or the LR. I can see that I have a 30 and a 20 amp free on my breaker next to each other. Would I be ok with 50 amps if I were going to get the LR model 3 or do I need 60 as recommended by Tesla? Or is that just if I were using their Wall Charger? If I use 50, does that just mean that I will get a slower charge on the LR or is there a chance for all the bad things I read here?

Remember, I'm a moron, I might not understand if you belittle me for not understanding.

There are lots of permutations. You first need to decide if you want to install a Tesla wall charger, or if you're going to use the mobile charger that you get with the car as a home charger.

 

[ucmndd]

A 14-50 socket implies that the wire from the breaker to the socket is rated at 240V/50A (or better) and that you have a 240v/50A breaker.

It really doesn't though. Code allows smaller breakers and wire. 14-50s are installed this way, typically at 40 amps, all the time. It's extremely common.

 

[eprosenx]

A 14-50 socket implies that the wire from the breaker to the socket is rated at 240V/50A (or better) and that you have a 240v/50A breaker.

This is completely misleading. I posted the exact relevant code sections upthread.

A 14-50 receptacle does NOT imply wire sufficient for 50 amps nor does it imply a 50a breaker.

It is extremely common to find 40a capable wire (say 8awg romex) and 40a breakers feeding NEMA 14-50 receptacles. This is completely code compliant if the intended load is a UMC Gen 2 for instance which maxes out at 32a continuous.

As I pointed out, code might even allow you to install a dedicated NEMA 14-50 on a 30a circuit with 10 gauge wire, but that is only if the intended load does not require any more than that. I don’t know of any devices that need 30a or less that have NEMA 14-50 plugs on them (they would generally have 14-30’s or 6-30’s). So this is a bit of a pedantic example.

Now it is a great idea to always install 50a capable wire and a breaker any time you install a 14-50 or a 6-50, but this IS NOT A CODE REQUIREMENT for an install supporting a UMC Gen 2.

 

[ucmndd]

I don’t know of any devices that need 30a or less that have NEMA 14-50 plugs on them (they would generally have 14-30’s or 6-30’s). So this is a bit of a pedantic example.

They do exist...

16A Level 2 EVSE LCS-20P with NEMA 14-50 | ClipperCreek

Not that I'm condoning a 14-50 with a 20 amp breaker...

 

[NickFie]

I read a post a while back where someone made a 20 ft cable with a 14-30 plug and 14-50 receptacle and kept it in their Model S for charging from a dryer outlet. For the new mobile chargers would that lead to a current overdraw?

I made two adapter cables so I can use my 6-50 welder’s extension cord with dryer outlets. I set the car to charge at 24 Amps in those situations.

All good AS LONG AS YOU SET PROPER CHARGE CURRENT in the car. The car remembers the charge current for the location. Also remembers that you can charge there.

The first time we drove to a destination far from a SuperCharger, navigation was very worried. It figured car would be stranded without enough power to get to a SuperCharger. It didn’t yet know I could charge at the destination. No problem on subsequent trips.

Charged at a relative’s house once. 14-50 outlet in the garage for industrial grade air compressor. Plugged in our Gen 1 adapter, figured I would be charging quickly. After a few minutes, charging stopped. 30-Amp breaker had tripped. Set car for 24 Amps, reset breaker and things were fine.

Lesson learned - verify breaker rating BEFORE charging.

 

[Alketi]

This is completely misleading. I posted the exact relevant code sections upthread.

A 14-50 receptacle does NOT imply wire sufficient for 50 amps nor does it imply a 50a breaker.

It is extremely common to find 40a capable wire (say 8awg romex) and 40a breakers feeding NEMA 14-50 receptacles. This is completely code compliant if the intended load is a UMC Gen 2 for instance which maxes out at 32a continuous.

@eprosenx follow the logic.

Can one put 15A wiring and a 15A breaker behind a NEMA 14-50 outlet?

Can one put a 20A breaker behind a NEMA 14-30?

So one can put any size breaker behind any size outlet, depending on how careful the current use model is?

What happens to the next guy???????

How does that make any sense??

The relevant code section is the Conductor size, not the Outlet section. 210.19 (A)(1)

Branch circuit conductors shall have the ampacity not less than the maximum load to be served.

A NEMA 14-50 serves 50A.

Further --

 

[ucmndd]

How does that make any sense??

I don’t believe the intent is to apply broadly to any branch circuit configuration, but 40A breakers are indeed explicitly allowed on 50A receptacles. My understanding is this is acceptable because there are no 40 amp NEMA receptacles, thus there is no real choice other than to upsize.

It’s right there in your own documentation, look closer:

A NEMA 14-50 serves 50A.

A NEMA 14-50 serves “up to” 50A. The “maximum load to be served” is situation dependent.

 

[Alketi]

I don’t believe the intent is to apply broadly to any branch circuit configuration, but 40A breakers are indeed explicitly allowed on 50A receptacles. My understanding is this is acceptable because there are no 40 amp NEMA receptacles, thus there is no real choice other than to upsize.

It’s right there in your own documentation, look closer:

View attachment 393056

And where does it state that -- code might even allow you to install a dedicated NEMA 14-50 on a 30a circuit with 10 gauge wire, but that is only if the intended load does not require any more than that.

How can the next "guy" possibly know what the original intent was?

Why are outlets different shapes to begin with??

 

[ucmndd]

And where does it state that -- code might even allow you to install a dedicated NEMA 14-50 on a 30a circuit with 10 gauge wire, but that is only if the intended load does not require any more than that.

He said “might” and to be honest I have no dog in that fight. Many things in the NEC are indeed subject to interpretation. My point is that the case of a 40A breaker on 50A receptacle is explicitly allowed (and extremely common). Thus the post by @M3BlueGeorgia that @eprosenx was responding to is certainly misleading.

How can the next "guy" possibly know what the original intent was?

This “next guy” generally starts by looking at the breaker panel.

 

[eprosenx]

@eprosenx follow the logic.

Can one put 15A wiring and a 15A breaker behind a NEMA 14-50 outlet?

Yes, if the intended device to be used on that dedicated outlet does not need more than 15a (12a continuous) and it had a 14-50 plug on it, it should be allowed by my reading of the code.

@eprosenx

Can one put a 20A breaker behind a NEMA 14-30?

Yes, under the same situation I called out above.

@eprosenx

So one can put any size breaker behind any size outlet, depending on how careful the current use model is?

What happens to the next guy???????

How does that make any sense??

Code does say that the breaker can not be greater than the rating of the receptacle.

I am not saying it is how I would structure the code, but this is my reading of the code (it is also not something I would do myself or recommend be done).

@eprosenx

The relevant code section is the Conductor size, not the Outlet section. 210.19 (A)(1)

Branch circuit conductors shall have the ampacity not less than the maximum load to be served.

A NEMA 14-50 serves 50A.

So the key here is this "Branch circuit conductors shall have the ampacity not less than the maximum load to be served." The "load to be served" is determined by the device you are going to plug into the receptacle, not the rating of the receptacle itself. So in the case of the UMC Gen 2 the load to be served is 32a when using the 14-50 adapter on the UMC Gen 2. That is a continuous load and so you have to calculate it as 125% of that - so 40a.


210.19(A)(4) I believe is the relevant section.

210.24 does not apply (the table you posted) since we are talking about dedicated (individual receptacle) circuits for EV charging.

 

[Alketi]

Yes, if the intended device to be used on that dedicated outlet does not need more than 15a (12a continuous) and it had a 14-50 plug on it, it should be allowed by my reading of the code.



Yes, under the same situation I called out above.



Code does say that the breaker can not be greater than the rating of the receptacle.

I am not saying it is how I would structure the code, but this is my reading of the code (it is also not something I would do myself or recommend be done).



So the key here is this "Branch circuit conductors shall have the ampacity not less than the maximum load to be served." The "load to be served" is determined by the device you are going to plug into the receptacle, not the rating of the receptacle itself. So in the case of the UMC Gen 2 the load to be served is 32a when using the 14-50 adapter on the UMC Gen 2. That is a continuous load and so you have to calculate it as 125% of that - so 40a.


210.19(A)(4) I believe is the relevant section.

View attachment 393062

210.24 does not apply (the table you posted) since we are talking about dedicated (individual receptacle) circuits for EV charging.

View attachment 393063

I posted the relevant section of the code detailing the minimum wire size required.

But, you're still saying that in your world, despite every outlet having a different shape on purpose, any outlet can have any random ampacity, depending on whatever the person of the moment determines is their use?

A 14-50 outlet can have (theoretical) 5A breaker and 5A wiring if your theoretical person decided all they're going to plug in is a light bulb??

 

[eprosenx]

I posted the relevant section of the code detailing the minimum wire size required.

But, you're still saying that in your world, despite every outlet having a different shape on purpose, any outlet can have any random ampacity, depending on whatever the person of the moment determines is their use?

A 14-50 outlet can have (theoretical) 5A breaker and 5A wiring if your theoretical person decided all they're going to plug in is a light bulb??

You posted table 210.24 which I posted the text of section 210.24 which explains what it is for in my last post. That table is NOT relevant to this discussion as it only applies to circuits that have two or more receptacles.

I am not saying "in my world". I am reading the code and I am explaining my interpretation of it as it pertains to dedicated circuits for a specific purpose. Please find the code section that says you can't use a 30a breaker and wire on a NEMA 14-50 if your intended load is this Clipper Creek unit:

16A Level 2 EVSE LCS-20P with NEMA 14-50 | ClipperCreek

Again, I would not recommend installing a circuit like this, but I am just saying the code appears to allow for it.

To your last comment (barring the fact that a 5a breaker is not typically available), yes, if your intended load is less than 5a and 5a wiring were actually a thing (it is not, 15a is the minimum rating) and it was a dedicated circuit with just the one receptacle for that singular purpose, then this would be allowed by the 2017 NEC.

 

[eprosenx]

I am a pretty smart guy, but a moron when it comes to electricity. I have been following this thread and my head spins. I didn't know if I should start my own thread because my question is a little different, but I'll try here.

I am having an electrician run a 240v line from my breaker to the garage where I will put in a NEMA 14-50 outlet. I haven't decided on whether I'll get the SR+ or the LR. I can see that I have a 30 and a 20 amp free on my breaker next to each other. Would I be ok with 50 amps if I were going to get the LR model 3 or do I need 60 as recommended by Tesla? Or is that just if I were using their Wall Charger? If I use 50, does that just mean that I will get a slower charge on the LR or is there a chance for all the bad things I read here?

Remember, I'm a moron, I might not understand if you belittle me for not understanding.

All great questions! Clearly you have done some research and are not a moron. ;-) This should be a safe place to ask questions!
So if you get the SR+ the charger (which is onboard the car) can do a max of 32 amps. If you get the LR it can do a max of 48 amps (if you feed it a power source that can provide that).

The UMC Gen 2 (the cord that comes with the car) can do a max of 32 "amps. So if you want to *max* your charging ability and you get the LR, you will need to buy some additional EVSE like the "Wall Connector. Even if you get just the SR+, I am a huge fan of buying something to dedicate at home so you can keep a UMC in the car with you at all times (though I have never needed my UMC unplanned - lots of folks just take it with them when going somewhere they know they will need it like an overnight trip to a friends house or vacation home).

So your fundamental decision will need to be whether you buy a "Wall Connector" and hardwire that, OR if you just get a NEMA plug installed and use a UMC.

Then you need to decide what size branch circuit and wire to deploy to feed your NEMA plug or Wall Connector. If you just do a NEMA plug with the UMC you could do a 15a, a 20a, a 30a, a 40a, or a 50a circuit (with various receptacle types and adapters that Tesla sells for $35 each). Generally we recommend a NEMA 14-50 on a 50a circuit (using the following directions) unless you don't have enough capacity in your panel/service as determined by a "load calculation". (note that this is different than determining if you have enough physical space in the panel)

https://www.tesla.com/sites/default.../NEMA_14-50_installation_guide_NA_US_2017.pdf

If you want go go the Wall Connector route (I personally love my Wall Connector a lot and recommend it often - it is only a little more $$$ compared to buying a second UMC), then you can install it on a 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, or 100 amp breaker depending on what capacity you have available on your electrical service, how much future proofing you want to do, and how much money you want to spend.

If you do get the LR and have enough capacity, then there is a good chance I would recommend a Wall Connector on a 60a circuit which (due to the 80% derate for continuous loads) will let you charge at the full 48a rate the car is capable of. This is precisely what I did. 6 AWG copper in conduit surface mounted from my panel to the Wall Connector outside.

Oh, and we have not talked about your driving habits... Depending on how much you drive and with what patterns you might be fine enough with a 20a 240v circuit, or we might advise you to go all the way to the 60a 240v circuit with a Wall Connector (but a 14-50 is a very good middle ground FWIW).

I should also address your comment about having a "30a and a 20a free". Are you saying you have a couple unused 240v breakers already in the panel? 240v breakers are the "double wide" ones typically as they need to touch two poles on the bus bar in the panel. 120v ones are half the width of the 240v ones. As long as you have a pair of spots next to each other you can install any 240v breaker from 15a to 100a in that spot (typically - exceptions may apply). Also, even if you think all your spots are full there are often ways we can shift things around to install "tandem" breakers that let you have to breakers in the place of a single one so it helps increase the density.

If you post pictures of all your panels we may be able to help provide some more advice!

Good luck and here is to hoping you get your car soon! They really are AMAZING!

 

[garth_angst]

eprosenx, wow, thanks. This helps me even more.
Oh, and my dumb comment about having a 20 and 40 next to each other...I just meant I have 2 slots next to each other (really didn't matter what amperage they were I guess). I just said it to say that I have room for a 2-pole breaker without having to do a reconfigure.

 

[LCR1]

Guys, I was proposing (strongly) going to 14-30 instead of 14-50.

Except you never said that you said the car knows what size circuit it's plugged into, when in fact it doesn't.

A 14-50 socket implies that the wire from the breaker to the socket is rated at 240V/50A (or better) and that you have a 240v/50A breaker.

Again, no it doesn't, it simply doesn't. Please stop commenting on these posts/ threads, you constantly hit "disagree" on posts that are factual with the laws of physics, the software parameters of the cars, and the relevant NEC, or, National Electric Code. These are all facts that will not change no matter how much you disagree with them. You're simply confusing people that are trying to learn how not to kill themselves and/or burn their homes down.

 

[LCR1]

I am a pretty smart guy, but a moron when it comes to electricity. I have been following this thread and my head spins. I didn't know if I should start my own thread because my question is a little different, but I'll try here.

I am having an electrician run a 240v line from my breaker to the garage where I will put in a NEMA 14-50 outlet. I haven't decided on whether I'll get the SR+ or the LR. I can see that I have a 30 and a 20 amp free on my breaker next to each other. Would I be ok with 50 amps if I were going to get the LR model 3 or do I need 60 as recommended by Tesla? Or is that just if I were using their Wall Charger? If I use 50, does that just mean that I will get a slower charge on the LR or is there a chance for all the bad things I read here?

Remember, I'm a moron, I might not understand if you belittle me for not understanding.

As others have mentioned there are a few ways to go about it.

• If you want the full 48A charge rate for your LR car the only way that is possible is the $500 wall charger direct wired to a 60amp breaker.
• If you want to just use the mobile cord that came with the car you can put in a 14-50 outlet on a 50 amp breaker although the cord is still limited to 32A (recommended)
• If you use the mobile cord that came with the car you can put it on a 14-50 outlet and a 40amp breaker since the cord is limited to 32A (not recommended)
• You could also install a 14-50 outlet with a 50Amp breaker, use the mobile cord you have now and eventually upgrade to a gen1 cord that gives 40 amp or buy a wall charger and limit it to 40amps

So take away points

• The LR can charge at 48amps and would need the wall charger to reach that point, the SR is limited to 32Amps and nothing will change that, so never a reason to get a wall charger in my opinion.
• the difference between 32A give around 25mph charge, 40A is 30mph and 48A is closer to 35mph. Is the additional cost of a wall charger for the LR model 3 worth an extra 10 or even 15mph charge? how often will you need to charge at 35-40mph vs 25? you'd still get 250+ miles of charge every night with the included mobile cord at 32amp