Existing Home Electric Versus Second EV Meter - Economics

[GRA]

A 30A circuit can pull 30 amps, or any load up to that. Right?

Yes, but the National Electrical Code (NEC) defines any level of load that lasts for more than 3 hours as a 'continuous' load, and as others have said, the circuit must be de-rated to only 80% of its maximum current if the load is going to be continuous. While a 30 amp circuit can handle 30 amps maximum for short periods of time, a load like a charging EV is considered continuous, so the circuit must be considered capable of handling no more than 80% of its maximum, or 24 amps, for that period. The same applies to any other circuit with a continuous load on it, which is why the portable 120 volt EVSE that comes with the car is limited to a max. current of 12 amps on a 15 amp circuit (15 x .8 = 12).

 

[bbrowncods]

A 30A circuit can pull 30 amps, or any load up to that. Right?

Yes, but the National Electrical Code (NEC) defines any level of load that lasts for more than 3 hours as a 'continuous' load, and as others have said, the circuit must be de-rated to only 80% of its maximum current if the load is going to be continuous. While a 30 amp circuit can handle 30 amps maximum for short periods of time, a load like a charging EV is considered continuous, so the circuit must be considered capable of handling no more than 80% of its maximum, or 24 amps, for that period. The same applies to any other circuit with a continuous load on it, which is why the portable 120 volt EVSE that comes with the car is limited to a max. current of 12 amps on a 15 amp circuit (15 x .8 = 12).

Alright. So given a 30A circuit I can charge forever at 24A but no more than 3 hours at 25A? I guess there has to be a line somewhere.
So I did the math. For the Leaf only: LeafSpy puts my total capacity right at 20Ahr (0%-100%). Charging at 6.6Kw that comes to:20/6.6=3.0 hours. Sounds like that would meet the mark of a continuous load(3 hours or more). EXCEPT at 2.5 hours the Leaf starts ramping down the amps to the low teens, and actually finishes at 0 to 6 amps for the last 20-30 minutes while balancing. This is not a continuous load by definition. And that is a worst case 0% to 100% charge. The only time that this has happened to me is when I ran this test.
In actuality this is further from a continuous load example than charging at 24A. Since 24A extends the charge time out an additional 30-45 minutes into the >3 hour limit of a continuous load, and is right at the limit of 80%. This allows additional time for heat to build up in the circuit, almost an hour after my circuit has powered down.

 

[Valdemar]

In any case this is a code violation and a safety concern. It is up to you if you can live with that, but I wouldn't allow it in my home. At least evaluate how hot the wires get, presence of splicing on the run from the panel to the outlet, type of wire and insulation temperature rating, perhaps get an AFCI-type breaker. Good luck.

 

[bbrowncods]

In any case this is a code violation and a safety concern. It is up to you if you can live with that, but I wouldn't allow it in my home. At least evaluate how hot the wires get, presence of splicing on the run from the panel to the outlet, type of wire and insulation temperature rating, perhaps get an AFCI-type breaker. Good luck.

Only if it is determined that an EVSE is automatically considered a continuous load. I don't see that anywhere in code. If it is there, I'll go to 24A.
I am operating safer at 27.5A @ <2.5 hours, than at 24A @ >3 hours. It is the time that makes the circuit continuous.

 

[AlanSqB]

The code isn't about actual use. It's about rated and potential use. Think about your car charging at that rate for 2.5 hours (it will be more than that as you don't get the full 6.6 at the battery) and then a friend or family member borrows your plug to charge their car while visiting you without you knowing extending the use by several hours.

You may say that can't happen, but the rules are set up for what could happen. As mentioned, it's up to you but there is a reason it doesn't meet code and if it's hard wired, wouldn't pass inspection.

 

[AlanSqB]

In any case this is a code violation and a safety concern. It is up to you if you can live with that, but I wouldn't allow it in my home. At least evaluate how hot the wires get, presence of splicing on the run from the panel to the outlet, type of wire and insulation temperature rating, perhaps get an AFCI-type breaker. Good luck.

Only if it is determined that an EVSE is automatically considered a continuous load. I don't see that anywhere in code. If it is there, I'll go to 24A.
I am operating safer at 27.5A @ <2.5 hours, than at 24A @ >3 hours. It is the time that makes the circuit continuous.

https://www.azmag.gov/Documents/pdf...-the-National-Electric-Code-Handout_69446.pdf

https://www.inkling.com/read/nation...ction-association/chapter-6/iii--installation

http://apps.necanet.org/files/NECA413EVSErecirculation2.pdf

 

[Eire32]

So we should put the EvSe upgraded leaf charger on a 30 amp fuse or what then?

 

[AlanSqB]

So we should put the EvSe upgraded leaf charger on a 30 amp fuse or what then?

Ingineer's EVSEUpgrade only pulls 20 amps as delivered.

 

[bbrowncods]

From your sources:
"Continuous Load. A load where the maximum current is expected to continue for 3
hours or more."
"Non-Continuous Load. A load where the maximum current is expected to continue for
less than 3 hours."
Emphasis is added by me.
My EVSE is operated as a non-continuous load. It is impossible for the Leaf being charged at 27.5A to exceed 3.0 hours at that amperage. By definition does not require a continuous load circuit.
In fact, I wonder why Nissan picked exactly 6.6Kw and 20Ah. Is it so that their customers could use standard 30A/240V circuits at the max charge rate?

 

[AlanSqB]

Best of luck to you.

 

[bbrowncods]

Best of luck to you.

What luck? It is clear what the definitions are and I have shown that a Leaf does not require a continuous load circuit. If it is code for a hard wire unit then so be it. Mine is not.

If there is a possibility of a Tesla pulling up and charging, or future proofing, or any number of reasons; then sure put in a 40A, 50A, or 60A circuit. But don't imply I am violating code or being unsafe by utilizing a 30A circuit at 27.5 A to charge my Leaf.

 

[johnrhansen]

Best of luck to you.

What luck? It is clear what the definitions are and I have shown that a Leaf does not require a continuous load circuit. If it is code for a hard wire unit then so be it. Mine is not.

If there is a possibility of a Tesla pulling up and charging, or future proofing, or any number of reasons; then sure put in a 40A, 50A, or 60A circuit. But don't imply I am violating code or being unsafe by utilizing a 30A circuit at 27.5 A to charge my Leaf.

while there is some debate exactly what side of the limit this setup is on, we can all agree that it is pretty darn close to it. There is zero safety factor. My permanent unattended installation uses a 40 amp circuit, because I don't want to take any chances. But I have charged on a 30 amp circuit with my portable setup. WHEN EVERYTHING IS NEW, nothing got overly hot, but it was quite warm after a few hours. Pretty much right at the top of my comfort level. Please if you do this, make sure you keep a close eye on a regular basis of the temperatures of all the connections, especially any 30 amp plugs and receptacles. It's a really bad if any wires are enclosed where they can't be inspected and no air is allowed to flow around them, and in aged installations where the quality and condition of the circuit is not completely known. The hotter something gets, the more expansion and contraction occurs, and the faster something is going to come loose.. I know I know.. its best not to do it at all, but it sounds like he's gonna do it anyway. I would never go to sleep in a house with a setup like that flowing current at that level.

 

[AlanSqB]

NEC 625.41 (formerly 625.14) defines an EVSE as a continuous load for the purposes of rating. The exception is if there is a hardware solution to manage the load in a way that does not exceed the rated capacity of the circuit. That solution does not include "I know I'm not going to plug it into a Tesla." It would include a "smart" EVSE that knows it's only allowed to pull so many amps for so long and adjusts itself accordingly.

So I'm not implying anything. I'm telling. However you can do whatever you like in your own house, but it is in violation of code and willingly exceeding that circuit capacity will have implications for a potential insurance claim especially since you mentioned you changed the device to make it work. Please don't tell anyone it's ok to do this.

If you have been running that load for a while and your breakers aren't tripping, that is also concerning.

Sorry if my former posts caused confusion. The links were hastily copied over in an effort to explain the situation when the code chapter is actually the best reference.

 

[Rauv]

If I can add one more point here: NEC Code set the bar for the absolute minimum requirements, not necessarily a good electrical design. Just touch the outside case of the charging circuit breaker after a full charge and see how warm (or hot) it feels to the touch. Maybe then the issue will hit home. Its all about the heat.

 

[bbrowncods]

Best of luck to you.

What luck? It is clear what the definitions are and I have shown that a Leaf does not require a continuous load circuit. If it is code for a hard wire unit then so be it. Mine is not.

If there is a possibility of a Tesla pulling up and charging, or future proofing, or any number of reasons; then sure put in a 40A, 50A, or 60A circuit. But don't imply I am violating code or being unsafe by utilizing a 30A circuit at 27.5 A to charge my Leaf.

while there is some debate exactly what side of the limit this setup is on, we can all agree that it is pretty darn close to it. There is zero safety factor.

Zero safety factor?! Really? So a 30 amp circuit installed by an electrician is unsafe if it has a non-continuous load applied to it? I am no where near a max load of 30A for 2 hours and 59 minutes. Which by the way is the limit for a non-continuous load. And NEC says that limit is safe.
The problem is we can't pick and choose what rules we want to follow. Either our electrical load is a continuous one or it is a non-continuous one. NEC does not designate portable EVSE's as continuous loads, and my instilation falls easily and safely as a non-continuous load.

 

[Valdemar]

Sigh...

 

[bbrowncods]

NEC 625.41 (formerly 625.14) defines an EVSE as a continuous load for the purposes of rating. The exception is if there is a hardware solution to manage the load in a way that does not exceed the rated capacity of the circuit. That solution does not include "I know I'm not going to plug it into a Tesla." It would include a "smart" EVSE that knows it's only allowed to pull so many amps for so long and adjusts itself accordingly.

All EVSE's have a set limit. One should set the limit (or buy one with a preset limit) of their EVSE to not exceed the the circuit onto which it is attached (NEC 625.41). My EVSE is set to 28A (30A is acceptable as well), the Leaf that I charge is set to 27.5A max from the factory, and the EVSE has a timer (as well as the Leaf). The Leaf will not accept 27.5 A for longer than 3 hours (I have tested this on a 6.6Kw SL).
This meets the "exception" of NEC 625.41 for a permenant installation (mine is not). This is a non-continuous load. And it didn't cost thousands for an electrician to come wire me a special EVSE circuit. It is not required.

I will tell everyone to get educated and make a proper assessment of their sutuation and not buy into the fear mongering that implies it is unsafe to have a EVSE charging at 27.5A on a 30A circuit just because it is an EVSE. Even if they own a Tesla.

Let me just add that the argument that the circuit needs to be inspected for degraded conditions, insulation, etc. applies to any type of load. Just because one uses 24A instead of 27.5A does not make it any safer.

 

[RegGuheert]

Almost the last option you'd think of!

Actually, it was the first option I suggested (way back on page 2):

As such, if you can get the utility to put new service and an EV meter ON THE GARAGE, then you may come out cheaper both up-front AND for your electricity rate. (But I doubt that is what they are offering.)

 

[Eire32]

Almost the last option you'd think of!

Actually, it was the first option I suggested (way back on page 2):

As such, if you can get the utility to put new service and an EV meter ON THE GARAGE, then you may come out cheaper both up-front AND for your electricity rate. (But I doubt that is what they are offering.)

True, however I had the first two electricians say that this option would be 'wayyy more money'. The third quote I got, the guy was like 'its less hassle for me so ill do it cheaper' plus the first two guys said just the drop from the power company would cost $500-600. It didn't. It was free.

So I was just going by what licensed electrician professionals were telling me. Goes to show you gotta take hold of everything yourself!

 

[Valdemar]

NEC 625.41 (formerly 625.14) defines an EVSE as a continuous load for the purposes of rating. The exception is if there is a hardware solution to manage the load in a way that does not exceed the rated capacity of the circuit. That solution does not include "I know I'm not going to plug it into a Tesla." It would include a "smart" EVSE that knows it's only allowed to pull so many amps for so long and adjusts itself accordingly.

All EVSE's have a set limit. One should set the limit (or buy one with a preset limit) of their EVSE to not exceed the the circuit onto which it is attached (NEC 625.41). My EVSE is set to 28A (30A is acceptable as well), the Leaf that I charge is set to 27.5A max from the factory, and the EVSE has a timer (as well as the Leaf). The Leaf will not accept 27.5 A for longer than 3 hours (I have tested this on a 6.6Kw SL).
This meets the "exception" of NEC 625.41 for a permenant installation (mine is not). This is a non-continuous load. And it didn't cost thousands for an electrician to come wire me a special EVSE circuit. It is not required.

I will tell everyone to get educated and make a proper assessment of their sutuation and not buy into the fear mongering that implies it is unsafe to have a EVSE charging at 27.5A on a 30A circuit just because it is an EVSE. Even if they own a Tesla.

Let me just add that the argument that the circuit needs to be inspected for degraded conditions, insulation, etc. applies to any type of load. Just because one uses 24A instead of 27.5A does not make it any safer.

Continuous load argument aside, there is no doubt that your circuit operates near its limit which is never a good thing as it leaves little room for error. The fact your load is active for prolonged periods of time only makes it worse. There were reports of Leafs drawing more current than they should on 110V due to faulty hardware. It is rarely a single thing that causes bad things to happen, but a combination of your Leaf drawing more than 27.5A, hot summer weather, old insulation, and a sticky breaker can be your recipe for a fire.