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40 Amp Circuit for UMC Gen 2

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#21
EVnut said:
Hmmm. Skipping the "outside" part for a moment, it bears pointing out that everything related to "disconnecting means" (readily accessible, locked open) seems to be solved with a receptacle and plug.

I bring this up due to all the discussion of the downsides of adding a pigtail to the HPWC, and how scary that can be. This is *not* a recommendation, merely a mention.

The plug is going to be right there, readily accessible. And once it is unplugged, it isn't going to accidentally plug itself back in. An additional benefit is that everybody knows how and where to break the circuit if needed.

(for the record, I'm using a NEMA 14-50p on my HPWC, and my 14-50R is on a breaker that's a a foot away from the HPWC. And did I mention my 8 gauge, non-Romex, properly temp-rated, up-to-code wire for the 50A circuit? :)
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So I also found last night in my newly discovered 2017 NEC 625 the following:

NEC 625.44 (C) - "Fixed Equipment - All other equipment shall be permanently wired and fixed in place to the supporting surface."

My reading of the code is that a "wall connector" counts as fixed equipment. It is certainly not "Portable Equipment", and I do not believe it can be considered "Stationary Equipment" (which can have a plug) since it requires tools to remove it and move it around.

So my apologies for being pedantic, but I believe that what you have described is not code compliant if it was installed today. (I absolutely believe what you have done is likely safe, but I just document this here for other folks that may stumble upon it later in searches) There are also extreme limits in NEC 625 around the length of pigtails where allowed. Like 12 inches as specified in NEC 625.17 (A) (3).

EVnut said:
Over 20 years ago, every EV charger (yes, these were chargers and not EVSEs) was "required" to be hard-wired. And for the past 20+ years, I've plugged in my chargers (and now EVSEs). Call me crazy, but I can't be without the flexibility that this provides. I have three 14-50R's in my garage, and being able to reconfigure my parking and charging instantly has proven to be worth it's weight in gold over the years, and many cars. The only downside for me is that I'm limited to a 50A circuit. But considering that every EV I've owned before the Tesla topped out at about 17 mph charge rate, I'm OK with the 37 mph of the Model 3 on a 50A circuit!
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Yeah, makes sense to me! I take it you have multiple plugs on the same circuit? Or are they all on different circuits?

Under the 2017 code you can't have more than one receptacle per circuit if they are intended for vehicle charging.

Thanks for all your insight btw!
 
#22
eprosenx said:
There is an interesting callout for "disconnecting means". Basically for equipment over 60 amps or that is over 150v (which all level 2 style chargers or the Tesla Wall Connector is)
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No, you are misreading this part related to the 150V. Here is the actual text:
"For electric vehicle supply equipment rated more than 60 amperes or more than 150 volts to ground, the disconnecting means shall be provided and installed in a readily accessible location."
A 240 voltage difference that an appliance uses is not 240 volts to ground. Residential electricity in your house is a 120 volts to ground system. Both hot legs are 120 volts to ground, but they are 240 volts relative to each other. That's why you never hear about the need for disconnects for any of these EVSEs that are 60A or less.

EVnut said:
And did I mention my 8 gauge, non-Romex, properly temp-rated, up-to-code wire for the 50A circuit? :)
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That sounds vaguely familiar...:p
 
#23
Rocky_H said:
No, you are misreading this part related to the 150V. Here is the actual text:
"For electric vehicle supply equipment rated more than 60 amperes or more than 150 volts to ground, the disconnecting means shall be provided and installed in a readily accessible location."
A 240 voltage difference that an appliance uses is not 240 volts to ground. Residential electricity in your house is a 120 volts to ground system. Both hot legs are 120 volts to ground, but they are 240 volts relative to each other. That's why you never hear about the need for disconnects for any of these EVSEs that are 60A or less.
Click to expand...

Yes, you are right. After I posted that I realized I read that wrong. I tried to go back and update the threads in which I mentioned this but I missed this one. The next paragraph down in the code was talking about 125v and 250v stuff (not in reference to ground) and I read that paragraph first.

Thanks for correcting the record! Good for future folks who come across this thread in the great Google cache. ;-)
 
#24
eprosenx said:
My reading of the code is that a "wall connector" counts as fixed equipment. It is certainly not "Portable Equipment", and I do not believe it can be considered "Stationary Equipment" (which can have a plug) since it requires tools to remove it and move it around.
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Oddly enough, I believe that I make the HPWC portable by adding a plug, and potentially hanging it on a hook (basically making it into a huge UMC). And until such a time when Tesla prohibits the addition of a plug, I'm not quite sure how that would fit in with Fixed Equipment.
So my apologies for being pedantic, but I believe that what you have described is not code compliant if it was installed today. (I absolutely believe what you have done is likely safe, but I just document this here for other folks that may stumble upon it later in searches) There are also extreme limits in NEC 625 around the length of pigtails where allowed. Like 12 inches as specified in NEC 625.17 (A) (3).
Click to expand...
I don't find your posts pedantic in the least. Probably because I'm equally OCD. :) I love discussions like this!

Thanks for bringing up "safe." In the same way that I deal with the vehicle code, I also prioritize "safe" over "law" when it comes to the NEC. Understanding the issues, repercussions and the science is more important than blindly following the code.

Yeah, makes sense to me! I take it you have multiple plugs on the same circuit? Or are they all on different circuits?
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I have separate breakers in a garage sub-panel for each circuit. I only have one 14-50R per circuit. Two are for EV charging, one is for welding.
 
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#25
Rocky_H said:
A 240 voltage difference that an appliance uses is not 240 volts to ground. Residential electricity in your house is a 120 volts to ground system. Both hot legs are 120 volts to ground, but they are 240 volts relative to each other. That's why you never hear about the need for disconnects for any of these EVSEs that are 60A or less.
Click to expand...

Ah! Great point. That had me scratching my head a bit, but I didn't worry about it too much just because I have *multiple* disconnects on all circuits that I use for my EV charging. Makes sense now!
 
#26
EVnut said:
Oddly enough, I believe that I make the HPWC portable by adding a plug, and potentially hanging it on a hook (basically making it into a huge UMC). And until such a time when Tesla prohibits the addition of a plug, I'm not quite sure how that would fit in with Fixed Equipment.
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Hah, sure! If not fixed in such a way that you can't remove it without tools then yes I agree! It could be classed as "Stationary Equipment" which can have a plug! Or I suppose you might even to be able to argue it is "portable", though I suspect "stationary" is a better definition (all three are called out in code). You still probably have severe limitations on cord length (like 12 inches max).

EVnut said:
I don't find your posts pedantic in the least. Probably because I'm equally OCD. :) I love discussions like this!

Thanks for bringing up "safe." In the same way that I deal with the vehicle code, I also prioritize "safe" over "law" when it comes to the NEC. Understanding the issues, repercussions and the science is more important than blindly following the code.
Click to expand...

Totally agreed. I generally try to follow code to the letter since it generally has very good reasons, but on a practical basis sometimes an exception or two has to be made. (especially for temporary stuff that only I have physical access to)

EVnut said:
I have separate breakers in a garage sub-panel for each circuit. I only have one 14-50R per circuit. Two are for EV charging, one is for welding.
Click to expand...

Nice! "Welding" Love it! I am sure that helps with the load calculations. ;-) (clearly you are sophisticated enough to make sure you don't have three EV's all charging at once at a rate that would stress that sub panel feeder)
 
#27
eprosenx said:
Totally agreed. I generally try to follow code to the letter since it generally has very good reasons, but on a practical basis sometimes an exception or two has to be made.
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The NEC is one thing, but the local ordinances is quite another. If I can ride for 12 minutes and be in a town that has different requirements for some electrical installations. Is it really a different set of dangers over there, than it is here? That's the sort of thing that makes me crazy. So yeah... safety first. Then code. I always try to *understand* the code, and the reasons. But some of them really are nuts. Where I can run conduit for a solar installation varies significantly from my town to the next. And this has nothing to do with electrical safety, only with convenience for some other public entities in town.
Nice! "Welding" Love it! I am sure that helps with the load calculations. ;-) (clearly you are sophisticated enough to make sure you don't have three EV's all charging at once at a rate that would stress that sub panel feeder)
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Yeah, with everything on full-bore, and me using multiple tools at once.... I'm still good. By design.

I love electricity. It's just sitting there quietly in the wall waiting to help me. And a bunch trickles down from my roof every day.
 
#28
EVnut said:
The NEC is one thing, but the local ordinances is quite another. If I can ride for 12 minutes and be in a town that has different requirements for some electrical installations. Is it really a different set of dangers over there, than it is here? That's the sort of thing that makes me crazy. So yeah... safety first. Then code. I always try to *understand* the code, and the reasons. But some of them really are nuts. Where I can run conduit for a solar installation varies significantly from my town to the next. And this has nothing to do with electrical safety, only with convenience for some other public entities in town.
Click to expand...

Yeah, agreed. Though for what it is worth on the "where you can run conduit for solar", there is one reason that I can understand it being different in two different towns. When your house catches fire they will often go to the roof and cut a ventilation hole to let them control the fire burn and attack it how they want. It can be really dangerous to cut into an energized high voltage DC cable that is a few inches below the roof. So the fire departments may be trained differently in the different municipalities to expect different installations. So it is a legit risk to the firefighters to not do it the way they "expect".

Of course with that being said, why can't we all just standardize and do it the same way???
 
#29
For what it's worth - I have a 6-50 outlet connected to a 40A circuit that was originally intended for an electric cooktop. The house is 20 years old and only had 3 wires going to the kitchen instead of 4, hence the use of the 6-50. The outlet was wired and installed by a licensed electrician that does EV chargers all the time, and I just passed my city inspection this week (the inspection basically amounted to the guy looking at my breaker, looking at my outlet, and looking at my car -- easiest inspection ever). So my 6-50 on a 40A circuit is definitely code-compliant.

The circuit is limited to 40A by the breaker. My car with a Gen 1 UMC will try to pull all 40A by default, so I have it limited in the settings to 32A. I've had no problems.
 
#30
eprosenx said:
Oh, I also need to call out that after I posted that last night I found NEC 625 which covers "Electric Vehicle Charging System". There are a lot of good nuggets in there. None of it negates what I said above, but it does provide clarity.

Specifically 625.40 makes it very clear "Each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets".

There is an interesting callout for "disconnecting means". Basically for equipment over 60 amps or that is over 150v (which all level 2 style chargers or the Tesla Wall Connector is) you have to have a disconnecting means in a "readily accessible" location and it must be able to be locked in the open position (i.e. to lock a breaker off so that you can work on the EVSE safely without fear of someone flipping back on).

What is unclear to me is if my install I just did is now compliant (I installed my wall connector outside without a disconnect switch). I presume that my breaker on the inside of the garage less than 10 feet away counts - but I am unclear). For sure I need to add one of those metal clip things that allows the breaker to be locked in the "off" position I guess.

This was 2017 code just FYI which is the latest.
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You've misread the code. It is "over 150v to ground" which is not the case for these units. Each leg of the 240v is only 120v to ground.
 
#31
CricTic said:
For what it's worth - I have a 6-50 outlet connected to a 40A circuit that was originally intended for an electric cooktop. The house is 20 years old and only had 3 wires going to the kitchen instead of 4, hence the use of the 6-50. The outlet was wired and installed by a licensed electrician that does EV chargers all the time, and I just passed my city inspection this week (the inspection basically amounted to the guy looking at my breaker, looking at my outlet, and looking at my car -- easiest inspection ever). So my 6-50 on a 40A circuit is definitely code-compliant.

The circuit is limited to 40A by the breaker. My car with a Gen 1 UMC will try to pull all 40A by default, so I have it limited in the settings to 32A. I've had no problems.
Click to expand...

Yeah, it seems pretty clear that a 50a plug on a 40a circuit is totally legit and legal, though if clearly the intended use case for the circuit is to charge a vehicle which will by default draw 40a then I suspect this makes it not code compliant. I don't think relying on manually setting the Tesla to 32a probably counts (I would think code would go against "nameplate" readings as printed on the tip of the UMC 6-50).

So my supposition is that even though the inspector signed off on it, due to the clearly intended load I suspect it is not code compliant. NEC tries to keep users from making potentially dangerous mistakes.

As an example, if you plugged a range in that needed a 50a circuit based on its nameplate to a circuit that was only 40a this would not be code compliant. Just because the homeowner promised to only run 3 of the 4 burners would not make it code compliant.

A Gen 2 UMC however would be completely fine...
 
#33
This whole mess could be avoided if there were NEMA 6-40 and 14-40 standards. Then 50A and 40A sockets would have been just like 30A sockets: you would use the same rating for the circuit breaker and socket under all circumstances. There would be no need for exceptions.

EVnut said:
Indeed. Doesn't that seem safer for everybody if there was consistency and agreement?
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#34
eladts said:
This whole mess could be avoided if there were NEMA 6-40 and 14-40 standards. Then 50A and 40A sockets would have been just like 30A sockets: you would use the same rating for the circuit breaker and socket under all circumstances. There would be no need for exceptions.
Click to expand...

Yeah. Or you could just require all 6-50 and 14-50 receptacles to have 50 amp capable wiring and breakers.

But I suspect both coming up with another receptacle type and making folks "overbuild" 40a circuits may be untenable.

To be honest, I think this never used to be much of an issue since these outlets were typically used for ranges/ovens/cooktops and were often installed by professionals even though they were plug-in. But now that we are using these for electric vehicles (which people tend to swap around more often since they are inherently mobile), there is more risk that someone say switches from a UMC Gen 2 (32 amp limited - so good on a 40a circuit) to a UMC Gen 1 (40 amp limited and needs a 50a circuit) without involving an electrician, but both fit in the same 50a plug...

I think we are on the cusp of EV's starting to become more mainstream and so you are going to see the average buyer become less fastidious and you will have a lot more vehicles out there so that is likely to drive more house fires due to these issues.

As it always does, the NEC will continue evolving...
 
#35
I agree that it is time to have a 40A standard. It seems that we just didn't need it before. It also seems that we do now! And wouldn't it be great if we had ONE connector that covered 30, 40, 50 A with the only difference being the shape of the neutral pin? The number of 30A "standards" is a bit crazy-making.
 
#38
Apart from all the wiring and code discussions, I think this is true:

#1: A new style UMC2 which is 32A max is fine going through a 14-50 wired to a 40A breaker. Best practice for a 40A circuit is to never pull more than 32A continuous load. (40*.8=32)

#2: If you have one of the older UMCs, or "fixed plug" UMC2 that call pull 40A, then you ought to have a 50A circuit (including 50A breaker) to feed the 40A continuous load (50*.8=40)

Personally I have a 40A wired 14-50 with a fixed plug UMC2, but I have my car set to 32A max charging at my location in the software.
I tested it very briefly at 40A, and it worked, but I quickly dialed back to 32A for regular use.
 
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