NEC 625.41 Overcurrent Protection EV Chargers

[jar546]

For a standard EV chargers overcurrrent protection for feeders and branch circuits must be 125% of the maximum load of the equipment for continuous loads. However, many of these chargers are adjustable. With that being said, NEC 625.42 says the service and feeders shall be sized in accordance with the product rating. However, if the fixed in place equipment is adjustable, (with certain restrictions) it is then allowable to adjust the feeder based on the current setting of the charger. This creates an issue.

Many electricians are now looking at this and using 625.42 as reasoning to reduce the size of the disconnect. We are saying that there is no direct correlation and if the intent was to allow the disconnect to be reduced in size, then 625.41 would have stated so or created an exception.

How do you view these sections for EV chargers?

 

[e hilton]

Problem I see is that the charger could be set for a low level with correspondingly sized conductors, and later it could be dialed up.

 

[wwhitney]

Problem I see is that the charger could be set for a low level with correspondingly sized conductors, and later it could be dialed up.

That's why 625.42 has language saying that the adjusted current setting may only be used for fixed-in-place equipment and when there is "Restricted access [to] prevent the user from gaining access to the adjusting means." So the installer is do the adjustment and is to be trusted to coordinate that adjustment with the sizing of the rest of the install. [Also, even if your scenario did happen, the breaker would trip to protect the smaller conductors. Any circuit can have an equipment malfunction that causes an overload.]

As to the OP, when 625.42's associated requirements are met, it specifies that the EVSE "shall be permitted to have ampere ratings that are equal to the adjusted current setting." In which case:

625.43 on disconnecting means refers to "rated over 60A". That would mean the adjusted current setting.

625.41 refers to the "maximum load of the equipment." Load in VA is just ampere rating * voltage rating, or in amps is just ampere rating. So the adjusted current setting would apply here as well. Note that if you have a 40A/240V EVSE, and never charge an EV on it with an onboard charger rated in excess of 7.2 kW, the largest actual load the circuit will ever see is only 30A. But the maximum load of the equipment is still 40A. That's the sense of the word "maximum" in 625.41, not the maximum setting possible under 625.42.

Also, if you interpret 625.41's reference to maximum load to mean the maximum setting possible under 625.42, that would completely defeat the allowance in 625.42 that "Sizing the service and feeder to match the adjusting means shall be permitted." If you have an 80A maximum rating EVSE that is adjusted down to 40A in accordance with 625.42, and if 625.41 were to still require a 100A OCPD, you obviously couldn't see the feeder for 125% * 40A = 50A. So the idea that 625.41 is referring to the maximum setting possible under 625.42 leads to the conclusion that the CMP has included useless allowances in 625.42 just to waste space.

Cheers, Wayne

 

[ICE]

What I am about to write is strictly my opinion and as you will soon find out, there are opposing views. Do not, and I repeat, do not take any of it as absolutely correct.

Early on the chargers had a dip switch that set the max output. Inspectors verified that the switch setting was appropriate for the circuit. A cover had to be removed with tools to access the dip switch. The chargers of today do not have a dip switch and the settings are achieved via an app. The owner can set the max output simply by manipulating an app.

Arguments have been made that only the installer has access to the password. Well that's false. Every time the power fails or the wifi goes out the charger needs to be "commissioned". Does anyone think that the owner will not be able to handle that?

A second argument is that the overcurrent device will protect the conductors if the demand exceeds the rating. It will do that... repeatedly until it won't. It is tripped and reset a few dozen times and just gives up. What then?

There is the premise that onboard technology will prevent a car from accepting a higher charge rate. While that might be true for some cars I doubt that is the case for them all and as an inspector I'm not playing guessing games.

The supply circuit shall match the maximum possible setting of any installed charger. That takes all the worry out of the equation. At that point I don't care who has access to what. I am not concerned with Tesla today and Rivian tommorrow. It's a done deal.

 

[wwhitney]

A second argument is that the overcurrent device will protect the conductors if the demand exceeds the rating. It will do that... repeatedly until it won't. It is tripped and reset a few dozen times and just gives up. What then?

You can do that today on any 120V circuit by just plugging in two hair dryers. Not a concern specific to EVSEs.

There is the premise that onboard technology will prevent a car from accepting a higher charge rate. While that might be true for some cars I doubt that is the case for them all and as an inspector I'm not playing guessing games.

Nothing in the J1772 standard that I'm aware of enforces that the EV current draw is not in excess of what the EVSE advertises to it. So this criticism applies to any EVSE at any setting. Any EV's onboard charger could suffer a failure and try to draw excess current.

The supply circuit shall match the maximum possible setting of any charger.

Not required by the NEC.

Cheers, Wayne

 

[ICE]

Not required by the NEC.

Maybe yes and maybe no. I have learned to pay attention when you weigh in on the electrical code. I also do not have the inclination to search for a rebuttal. I will say this: If as you claim, there is no requirement in the NEC that matches my opinion, well that is a mistake on the part of the NEC.

Please note that I added a disclaimer to my post so as to not dissuade anyone from following the code, letter by letter. I also added the word 'installed' before the word 'charger'.

 

[Yikes]

See also this somewhat related thread:
https://www.thebuildingcodeforum.co...n-gfci-for-ev-chargers-in-upcoming-nec.37525/