Installing a Nema 14-50 on a 30 Amp Breaker

[Alketi]

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.

First, yes, 40A wiring is allowed on NEMA 14-50 per the table as @ucmndd mentioned. Perhaps this is some of the confusion. However, 30A is not. 20A is not. etc.

@eprosenx the relevant code is what we both quoted. 210.19 (A)(1)

The difference in interpretation is of the following sentence:

(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served.

The receptacle-type determines the maximum load to be served. i.e. what anyone might ever plug into that outlet.

The maximum load to be served is not whatever random person #1 tells the electrician on some random day. i.e. "I'm only going to use this outlet with a lamp, I promise."

 

[M3BlueGeorgia]

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



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.

Rubbish !!!
What I said is completely valid:
"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."

If you see a 14-50 socket, you should be able to presume to plug in an appliance needing 240v/50A without causing an electrical fire in your house.

If your cabling and/or breaker can only rated for 240v/30A, then use a damn 14-30 socket.

 

[wcorey]

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.

And that's an excellent point. If you use it as a home charger it won't be available to use on the road. A second MCU is $300. A wall charger is $500 and you can get the full 48a, not 32a.

 

[LCR1]

Rubbish !!!
What I said is completely valid:
"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."

If you see a 14-50 socket, you should be able to presume to plug in an appliance needing 240v/50A without causing an electrical fire in your house.

If your cabling and/or breaker can only rated for 240v/30A, then use a damn 14-30 socket.

Find me a 40A socket/ receptacle/ outlet for people to use on their stove/range, I'll wait. Until then please shut your mouth about things you obviously have no idea in which you're saying. It is perfectly acceptable to have 40amp breaker on a 40amp wire going to a 50amp socket, get over it.

Reminder, you clicking disagree doesn't change fact or reality.

 

[eprosenx]

First, yes, 40A wiring is allowed on NEMA 14-50 per the table as @ucmndd mentioned. Perhaps this is some of the confusion. However, 30A is not. 20A is not. etc.

@eprosenx the relevant code is what we both quoted. 210.19 (A)(1)

The difference in interpretation is of the following sentence:

(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served.

The receptacle-type determines the maximum load to be served. i.e. what anyone might ever plug into that outlet.

The maximum load to be served is not whatever random person #1 tells the electrician on some random day. i.e. "I'm only going to use this outlet with a lamp, I promise."

Totally agreed that this is a difference in how that is interpreted. Thank you for framing the conversation that way.

So I have been reading and interpreting the code for quite a while now and everything I have read leads me to believe that you start with the load that is intended to be served (even when talking about cord and receptacle attached equipment) and then do your calculations from there (so the load to be served is the actual end device, not the rating of the receptacle you are installing). The challenge here is that I am not sure I can point to one place that definitively explains that. I will have to do some research to see if I can find an article or something from a respected source that walks through this and post it here.

One bit of evidence to support my thesis is precisely the 40a circuit situation. It is clearly allowed in some situations according to the 210.24 table. If you always had to install wire and a breaker sufficient for the max load that could be plugged into a receptacle then a 40a breaker would never be allowed.

Now of course I just used that as an example, but I am again going to point out that the whole 210.24 table DOES NOT APPLY to EV charging since all EV charging is required to be on a dedicated circuit with a single receptacle (per I think NEC 625). 210.24 only applies to circuits with more than one receptacle on them.

Rubbish !!!
What I said is completely valid:
"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."

If you see a 14-50 socket, you should be able to presume to plug in an appliance needing 240v/50A without causing an electrical fire in your house.

If your cabling and/or breaker can only rated for 240v/30A, then use a damn 14-30 socket.

I agree that for all new installations it would be smart to require a 14-50 socket to be backed by a 50a breaker and wire, but that is just your and my opinion. It is NOT how the code is written today.

The NEC is all about balancing industry concerns about installed cost with life safety and damage concerns when things are not done adequately. The code typically tries to make sure things are done to the minimum spec necessary (plus a margin for safety), but it avoids going above and beyond. So if a device only draws 32a continuous code does not want to force the circuit to be planed as a 50a circuit (only a 40a one due to the 125% uprating for continuous loads). The difference is 8 gauge wire vs. 6 gauge wire. The cost difference is decently large.

Note that the NEC is usually assuming say an industrial kitchen or a machine shop where the exact devices to be connected are known (and they usually have an electrician on staff or readily available any time they get new equipment or need to move things around). EV's I think are a newer beast that they have not quite figured out yet. I think individuals are more likely to "upgrade" their EVSE (get a different car, etc...) without engaging with a professional. So I would not be surprised if we see a code change here in the future to require 50a circuits on 14-50's installed for EV charging purposes.

Note that I think this is a big reason Tesla down-rated from 40a to 32a when going from the UMC Gen 1 to UMC Gen 2. It think by doing that it eliminated the hazard of 14-50 receptacles that only had a 40a backing circuit (it also made things cheaper/lighter, etc...)

 

[eprosenx]

And that's an excellent point. If you use it as a home charger it won't be available to use on the road. A second MCU is $300. A wall charger is $500 and you can get the full 48a, not 32a.

And if you buy the Wall Connector you avoid the over $100 upcharge to install a 50a GFCI breaker (not required with the Wall Connector but it is required with a 14-50 receptacle), you also avoid the receptacle cost ($10-$80 depending on if you get the good one or not), plus the Wall Connector includes a cable management setup (extra $$$ if you just do a second UMC - Tesla buys a wall holder that many folks buy).

So if you are planning on buying a second UMC to keep one in the car at all times, the Wall Connector is not much more expensive, I would generally just go that route.

 

[SoundDaTrumpet]

And if you buy the Wall Connector you avoid the over $100 upcharge to install a 50a GFCI breaker (not required with the Wall Connector but it is required with a 14-50 receptacle), you also avoid the receptacle cost ($10-$80 depending on if you get the good one or not), plus the Wall Connector includes a cable management setup (extra $$$ if you just do a second UMC - Tesla buys a wall holder that many folks buy).

So if you are planning on buying a second UMC to keep one in the car at all times, the Wall Connector is not much more expensive, I would generally just go that route.

+1 @eprosenx The problem with NEMA 14-50 is you can't outright control or limit the charge rate (via hardware). I am attempting to add a Wall Connector while keeping my non-Tesla charger functional AND keeping under the 200A service under NEC load calc. I have a smart non-Tesla NEMA 14-50 plug-in charge station, and manufacturer says you can turn down the amperage by software. This doesn't pass logic. I have no main breaker on my service so NEC load calc play huge part. I plan to use a mechanical interlock so only one charger may be used at a time. Later on if I do have two EVs say a Tesla and non-Tesla, I may have to drop the Tesla Wall Connector to 15A; otherwise, changing the NEMA 14-50 breaker to 20A doesn't work because the wire is too large... bad bad. Software glitch, the breaker does trip... fire fire fire. Remind me that the NEC is NFPA 70 (National FIRE PROTECTION Association).

 

[M3BlueGeorgia]

Find me a 40A socket/ receptacle/ outlet for people to use on their stove/range, I'll wait. Until then please shut your mouth about things you obviously have no idea in which you're saying. It is perfectly acceptable to have 40amp breaker on a 40amp wire going to a 50amp socket, get over it.

Reminder, you clicking disagree doesn't change fact or reality.

Dragging you back to the original subject of this discussion, which was "
Installing a Nema 14-50 on a 30 Amp Breaker
", which it what I was discussing. Basically don't install 14-50 socket on a 30A breaker, use 14-30 instead.

 

[Alketi]

I messaged the NEC on clarification of rule 210.19 (A)(1). I'm not sure if they'll respond, but will post back here if they do.

 

[LCR1]

Dragging you back to the original subject of this discussion, which was "
Installing a Nema 14-50 on a 30 Amp Breaker
", which it what I was discussing. Basically don't install 14-50 socket on a 30A breaker, use 14-30 instead.

Except, yet again, that's not what you said. In case you forgot what you said I've made bold the applicable areas below.

Rubbish !!!
What I said is completely valid:
"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."

If you see a 14-50 socket, you should be able to presume to plug in an appliance needing 240v/50A without causing an electrical fire in your house.

If your cabling and/or breaker can only rated for 240v/30A, then use a damn 14-30 socket.

You mentioned nothing about 30 amp breakers in that line and that line is incorrect no matter how you spin it. If you see a 14-50 socket you should not be able to presume it's all 50amp because NEC specifically allows you to not have 50 amp anything hooked to a 14-50. Therefore a person who actually knows what they are talking about would know that a 14-50 needs to be verified before plugging anything in. But, feel free to disagree with facts and your own quotes

 

[davewill]

+1 @eprosenx The problem with NEMA 14-50 is you can't outright control or limit the charge rate (via hardware). I am attempting to add a Wall Connector while keeping my non-Tesla charger functional AND keeping under the 200A service under NEC load calc. I have a smart non-Tesla NEMA 14-50 plug-in charge station, and manufacturer says you can turn down the amperage by software. This doesn't pass logic. I have no main breaker on my service so NEC load calc play huge part. I plan to use a mechanical interlock so only one charger may be used at a time. Later on if I do have two EVs say a Tesla and non-Tesla, I may have to drop the Tesla Wall Connector to 15A; otherwise, changing the NEMA 14-50 breaker to 20A doesn't work because the wire is too large... bad bad. Software glitch, the breaker does trip... fire fire fire. Remind me that the NEC is NFPA 70 (National FIRE PROTECTION Association).

Why does turning the non-Tesla EVSE down not work? The load calc is based on the equipment installed, not the size of the breakers. You should be able to turn the EVSE down and clear headroom in your load calc withouth changing the breaker or the wire. You could also use a pigtail to adapt the larger wire to a smaller breaker if need be.

 

[miimura]

Why does turning the non-Tesla EVSE down not work? The load calc is based on the equipment installed, not the size of the breakers. You should be able to turn the EVSE down and clear headroom in your load calc withouth changing the breaker or the wire. You could also use a pigtail to adapt the larger wire to a smaller breaker if need be.

I think it's reasonable for an inspector to reject an installation that only falls within the load calc by virtue of a software setting. At a minimum I would think a hardware setting like the one in the Tesla Wall Connector could be required in order to pass inspection. It would also be reasonable to require downsizing the breaker to match the EVSE hardware setting.

 

[SoundDaTrumpet]

Why does turning the non-Tesla EVSE down not work? The load calc is based on the equipment installed, not the size of the breakers. You should be able to turn the EVSE down and clear headroom in your load calc withouth changing the breaker or the wire. You could also use a pigtail to adapt the larger wire to a smaller breaker if need be.

The equipment installed is a 32A EVCS. There is no turn pot on the unit. It is done via software app. There is no guarantee that the software is buggy or the manufacturer's API goes haywire (or hacked). Software likely not listed by a national test lab. Here's other evidence in practice: (1) Tesla Powerwalls backfeed included when sizing the electrical work. Tesla currently software limits to prevent charging to grid, so why include backfeed? (2) Unplugged dryer load should be included despite using a natural gas dryer. Tesla included this load. What if the new tenant wants to use a electric dryer and the cognizant tenant is unavailable or forgot. For pigtails, not sure about that inside panelboards.

Anybody well versed with using a Mechanical Interlock on a Branch Circuits? Feeding two chargers, but rarely will switch between the two. Two charge station types occupy same charge location.

 

[eprosenx]

I think it's reasonable for an inspector to reject an installation that only falls within the load calc by virtue of a software setting. At a minimum I would think a hardware setting like the one in the Tesla Wall Connector could be required in order to pass inspection. It would also be reasonable to require downsizing the breaker to match the EVSE hardware setting.

So I totally agree with you on the first part. I think just a software setting in the Tesla car itself that depends on GPS location and is set by a "laymen" (i.e. any driver) should not be sufficient. I do absolutely think that the hardware setting requiring a bunch of special torx screws is totally sufficient. There are tons of cases where you have larger breakers on a circuit but you calculate it as if it was a lower # on the load calc end of things. I am kind of on the fence about devices that have a max supply set in software, but say some custom special dealer software that only maintenance techs have. If UL rated I think I could be onboard with that being sufficient for load calc purposes. (I am just expressing personal opinions on this topic - not actual code references)

The equipment installed is a 32A EVCS. There is no turn pot on the unit. It is done via software app. There is no guarantee that the software is buggy or the manufacturer's API goes haywire (or hacked). Software likely not listed by a national test lab. Here's other evidence in practice: (1) Tesla Powerwalls backfeed included when sizing the electrical work. Tesla currently software limits to prevent charging to grid, so why include backfeed? (2) Unplugged dryer load should be included despite using a natural gas dryer. Tesla included this load. What if the new tenant wants to use a electric dryer and the cognizant tenant is unavailable or forgot. For pigtails, not sure about that inside panelboards.

Anybody well versed with using a Mechanical Interlock on a Branch Circuits? Feeding two chargers, but rarely will switch between the two. Two charge station types occupy same charge location.

I do agree on the unplugged electrical dryer still counting toward the load calcs. I think either you need to disconnect the wires at the receptacle end, or better yet, at the breaker end in order for it to not count against the load calcs (basically it should require a professional to hook back up who might consider the load calcs again).

So note that there are a couple of things in the code you should be aware of:

I know in commercial (and I think this applies to residential as well), you can use *actual* consumption #'s in order to evaluate if you can add more load in lieu of the calculations. So if you have a years worth of data for instance (there are ways around this too) you can use it to show you are vastly below the load limits and that you should be allowed to add a new device that might otherwise violate the paper load calcs.

Additionally, there are provisions for "non-coincident loads" where if you have two things that won't ever be operated at the same time you can just calculate for the greater of the two loads. What is interesting about this is that there is no actual hard requirement I am aware of to interlock the two. It is like a one-liner in the code. So I have a NEMA 14-50 receptacle as a backup for my Wall Connector. When my install was inspected the inspector did briefly chat with me about load calcs and signed off without getting into any math. <shrug>

On the interlock bit: Usually the interlock kits are for the main breaker plus a branch breaker (not two branch breakers). We have seen folks use a two position breaker panel with an interlock kit on it for this exact use case before. Somewhere on these forums is a thread on that with pictures...

 

[garth_angst]

And if you buy the Wall Connector you avoid the over $100 upcharge to install a 50a GFCI breaker (not required with the Wall Connector but it is required with a 14-50 receptacle), you also avoid the receptacle cost ($10-$80 depending on if you get the good one or not), plus the Wall Connector includes a cable management setup (extra $$$ if you just do a second UMC - Tesla buys a wall holder that many folks buy).

So if you are planning on buying a second UMC to keep one in the car at all times, the Wall Connector is not much more expensive, I would generally just go that route.

ok, good point. More to think about.
So...if I want to go the route of the Wall Charger, can I just add this into my main breaker, since I don't currently have a 60amp?

Square D Homeline 60 Amp 2-Pole Circuit Breaker-HOM260CP - The Home Depot

Or do I need a special 60amp breaker?

And if I only went with the SR+, will it handle dialing down the charger to 32amps from the Wall Charger on it's own?

 

[destructure00]

ok, good point. More to think about.
So...if I want to go the route of the Wall Charger, can I just add this into my main breaker, since I don't currently have a 60amp?

Square D Homeline 60 Amp 2-Pole Circuit Breaker-HOM260CP - The Home Depot

Or do I need a special 60amp breaker?

And if I only went with the SR+, will it handle dialing down the charger to 32amps from the Wall Charger on it's own?

That's the one I put in my panel for my HPWC. Is your panel Square D?

 

[wcorey]

And if I only went with the SR+, will it handle dialing down the charger to 32amps from the Wall Charger on it's own?

If you use a wall charger your Model 3, regardless of trim, will charge at 48a. <- apparently that is incorrect for SR and MR. They are 32a.

Look at tesla.com/charge In NY, I'm pretty sure Tesla can recommend electricians in your area completely familiar with the Wall Charger. To my knowledge it uses a standard 60a circuit with a standard 60a breaker, as opposed to GF. It doesn't need an exposed outlet. In CT, garage outlets have to be on a GF circuit. To your question though. The Wall Charger will recognize your Model 3. The same Wall Charger, on a 100a line can charge a Model S with the 72a inverter as well as a Model 3 that only has a 48a inverter, or 32a inverter.

 

[LCR1]

If you use a wall charger your Model 3, regardless of trim, will charge at 48a.

False, Only the long range comes with a 48A charger, MR and SR have a 32A charger.

EDIT: So from the factory the LR has a 48A charger and is limited by the 32A cord and you need a Gen1 cord to get 40A or a wall connector to get the full 48A.

The MR and SR have a 32A charger that matches the 32A cord. Plugging in a wall connector does nothing.

 

[wcorey]

False, Only the long range comes with a 48A charger, MR and SR have a 32A charger.

EDIT: So from the factory the LR has a 48A charger and is limited by the 32A cord and you need a Gen1 cord to get 40A or a wall connector to get the full 48A.

The MR and SR have a 32A charger that matches the 32A cord. Plugging in a wall connector does nothing.

I stand corrected. I have a LR AWD
I have made the appropriate edits.
Thank you for clarifying that.

 

[LCR1]

ok, good point. More to think about.
So...if I want to go the route of the Wall Charger, can I just add this into my main breaker, since I don't currently have a 60amp?

Square D Homeline 60 Amp 2-Pole Circuit Breaker-HOM260CP - The Home Depot

Or do I need a special 60amp breaker?

And if I only went with the SR+, will it handle dialing down the charger to 32amps from the Wall Charger on it's own?

If that install is going in your garage, then the one you listed is fine, as long as you install bigger than 50 amps, which 60 amps is. If you decide to install a 50 amp or smaller then you need a special GFCI breaker.