EV Charger 2017 vs 2020 and 2023

[Dennis Alwon]

This was told to me by the NC state chief engineer.

According to the 2017 NEC if you have a car charger that can be wired at different amperages then you must wire the charger at the highest level. For example, the house only has enough power to wire the charger at 240v 20 amps but the charger can be wired to 60 amps. Based on the 2017, he said we would have to wire the unit at 60 amps with #6 wire and a dp 60 breaker. This seems insane. A 20 amp unit being protected at 60 amps.

Now for the 2020 or the 2023 code he said we can wire it at the 20 amp level with a dp 20 breaker and #12 wire.


2023Nec

625.42(B) EVSE with Adjustable Settings.
EVSE with restricted access to an ampere adjusting means complying with 750.30(C) shall be permitted. If adjustments have an impact on the rating label, those changes shall be in accordance with manufacturer’s instructions, and the adjusted rating shall appear on the rating label with sufficient durability to withstand the environment involved. EVSEas referenced shall be permitted to have ampere ratings that are equal to the adjusted current setting.

750.30(C)(3) Settings.
Adjustable settings shall be permitted if access to the settings is accomplished by at least one of the following:

• (1)Located behind removable and sealable covers over the adjustment means
• (2)Located behind a cover or door that requires the use of a tool to open
• (3)Located behind locked doors accessible only to qualified personnel
• (4)Password protected with password accessible only to qualified personnel
• (5)Software that has password protected access to the adjusting means accessible to qualified personnel only

I get the 2023NEC but does the 2017 interpretation make sense to you? It seems to say what the chief told me but isn't it wrong to put a 20 amp unit on a 60 amp breaker even with the proper wire? We are in transition from the 2017 to the 2023 but it wont be until August before it will happen. The funny thing is we can choose which code to use if we specify on the permit which code we will wire to.

2017

625.41 Overcurrent Protection.
Overcurrent protection for feeders and branch circuits supplying equipment shall be sized for continuous duty and shall have a rating of not less than 125 percent of the maximum load of the equipment. Where noncontinuous loads are supplied from the same feeder, the overcurrent device shall have a rating of not less than the sum of the noncontinuous loads plus 125 percent of the continuous loads.

 

[wwhitney]

This was told to me by the NC state chief engineer.

According to the 2017 NEC if you have a car charger that can be wired at different amperages then you must wire the charger at the highest level. For example, the house only has enough power to wire the charger at 240v 20 amps but the charger can be wired to 60 amps. Based on the 2017, he said we would have to wire the unit at 60 amps with #6 wire and a dp 60 breaker. This seems insane. A 20 amp unit being protected at 60 amps.

Take the case of a unit with dip switches inside. Changing the dip switch just changes what current the EVSE tells the car it's allowed to draw. The EVSE itself is still rated to handle 60A. If everything upstream is sized for 60A, there's no safety issue. In other words, taking a compliant 60A installation with the dip switches set to 60A, and then changing the dip switches to 20A doesn't introduce any new hazards.

On the other hand, I disagree with this interpretation of the 2017 NEC. It relies on deciding that "maximum load of the equipment" means "maximum load for any possible equipment configuration" as opposed to "maximum load of the installed configuration." The latter is the more reasonable interpretation.

Cheers, Wayne

 

[retirede]

But it’s not “a 20A unit.” It’s a 48A unit dialed down to 16A. The unit is designed to be installed on a 60A circuit regardless of the setting.
It seems like a waste. You’d think he would allow an installation that complies with 2023 since it’s coming shortly.

 

[hillbilly1]

North Carolina has some weird interpretations, like for a while, they considered a light pole or a generator as a structure. If it is protected by a 20 amp circuit, if someone changes the output rate, it will eventually trip the breaker protecting the 20 amp wire. It’s just one of those “my rules, because I’m king deals”.

 

[Dennis Alwon]

Take the case of a unit with dip switches inside. Changing the dip switch just changes what current the EVSE tells the car it's allowed to draw. The EVSE itself is still rated to handle 60A. If everything upstream is sized for 60A, there's no safety issue. In other words, taking a compliant 60A installation with the dip switches set to 60A, and then changing the dip switches to 20A doesn't introduce any new hazards.

On the other hand, I disagree with this interpretation of the 2017 NEC. It relies on deciding that "maximum load of the equipment" means "maximum load for any possible equipment configuration" as opposed to "maximum load of the installed configuration." The latter is the more reasonable interpretation.

Cheers, Wayne

That makes sense.

But... IN the 2017 it does state the maximum load of the equipment

Overcurrent protection for feeders and branch circuits supplying equipment shall be sized for continuous duty and shall have a rating of not less than 125 percent of the maximum load of the equipment.

 

[wwhitney]

But... IN the 2017 it does state the maximum load of the equipment

Yes, that's what I said in the second paragraph of my post.

The more reasonable interpretation to me is "maximum over all possible EVs connected, while keeping the circuit and internal EVSE configuration fixed." As opposed to "maximum including the possibility of changing the internal EVSE configuration."

Cheers, Wayne

 

[jaggedben]

The equipment itself has (virtually) no actual load anyway. The actual load is the vehicle. Which is just a point in favor of saying that the 2017 wording is vague and general enough that interpreting it in the manner permitted by 2023 is perfectly reasonable. Claiming that the phrase 'max load of the equipment' has a precise meaning is less reasonable. Let the installer and AHJ look to the 2023 code to inform the meaning of that phrase.

 

[Dennis Alwon]

The equipment itself has (virtually) no actual load anyway. The actual load is the vehicle. Which is just a point in favor of saying that the 2017 wording is vague and general enough that interpreting it in the manner permitted by 2023 is perfectly reasonable. Claiming that the phrase 'max load of the equipment' has a precise meaning is less reasonable. Let the installer and AHJ look to the 2023 code to inform the meaning of that phrase.

I am retired but someone I know called me about this and they made him change it after he had done 20 of them in the past with no red tag. The only one I wired that was adjustable, was many years ago and fortunately, they wanted it wired for the max--80 amps so it wasn't an issue.

 

[Fred B]

I've done some that were adjustable at the HO side (HO bought their own unit) and for those I would wire to the max potentially connected to. If size would not be technically available for the service I wouldn't hesitate to add the lower breaker size and a warning to the HO not to set it to higher than the breaker size. But the units I typically had the electrician set and lock out to a determined max level, these could be wired to sizing based on the locked out level. Either would be different as to "maximum load of the equipment" for code compliance, as the one type can be locked by the installer the other not. "Maximum load" applied vs "maximum load" potential are two different things.

 

[NoahsArc]

I can plug a jerry-rigged 50A welder into a 15A outlet, should all outlets have #6 wire in a house now?
The cars can charge at 1000A rates if connected to a DC charger, should all EV circuits be parallel 750s now?

Nonsense. OCPD protects from owners messing with dipswitches.
If owners insist on changing the OCPD too, then there's nothing you can do proactively if they're that suicidal.

Regardless, I always bring #6s for EV circuits for future proofing if nothing else, it's not a huge price hike over #8s.