Electric vehicle circuit sizing (NM Cable)

What size wire and breaker do you need for a 48A electric vehicle supply equipment (charger)? Depends. Are you using Romex (NM Cable)?

[@ElectricalCodeCoach]

Excellent! This is a very common question and a huge misunderstanding!!

[@Jonacarpenter]

Great explaining the code and filling in the questions.👍

[@ElectricRob]

Hello Ryan - just ran across your channel and this video today - subscribed! I am an electrical engineer designing commercial projects, and always like to see different interpretations/explanations of electrical code issues, since as you know, some code language can be a bit confusing and interpreted differently. But great video - you cover a subject that I also have seen misunderstood by many. I'd also like to throw into this discussion an additional scenario that can further complicate EV charging equipment supply sizing - State modifications to the NEC (similar to what it looks like New Jersey is doing). Out here in Oregon, the state issued a "Statewide Alternate Method No. 09-01" for calculating the "demand factor" of single and multiple EVSE's with a table similar to multiple ranges or even dwelling units. To summarize, the ruling explains that "Considering EV charging equipment 'continuous loads" assumes that all charging equipment is likely to operate at full rated load for three hours or more. Testing data shows that charging currents are substantially below the full rated load and that cycle times typically do not exceed three hours." So it's interesting to note that they require only a 100% demand factor (in lieu of the NEC-stated 125%) for even a single charge point up to 4 points, and for 5 to 8 charge points only a 90% demand factor, and so on. So to a point I saw in a previous comment, using #6 NM should not actually be a safety issue in use (even though it technically would not meet NEC in practice for that location). But for example, in neighboring Washington State, we follow the "default" NEC ruling you cover nicely in your video.

[@chadgerman7467]

Love this!!! Thank you Ryan, I shared this video with all of our electrical instructors. This video is clear and concise

[@fordsbetter3496]

Thank you! I keep saying this I don’t understand why people don’t understand this

[@ElectricalTime]

Hi Ryan, thanks for continuously making these great NEC code videos, they are very much appreciated. Steve Kavallaris

[@The360Electrician]

Always answering the tough questions. Thank you

[@Michael046145]

I saw you on Electrical Code coach! You two are my fav!

[@bobbyb2952]

Thank you for the video Ryan!

[@dwayne7356]

Thank you for this explanation. I am not licensed but I understand the basic 120v residential circuits. I know what I don't know, which is a lot. I would never try to install an EVSE although I believe I could correctly. But, your explanation will allow me to ask the right questions for my electrician if I do not think it is right. I have had an electrician once install equipment not in accordance with the manufacturers instruction and it got passed by the electrical inspector. In all fairness to the electrical inspector, the only way he would have know is if he disassembled the light control box to my pool. It clearly stated to size the breaker at 15 amp, not 20 amps. (I read everything weeks before it was installed by the pool contractor's electrician.)

[@HomeWire-zd4yu]

You look tired. Your stuff is awesome, just don't forget to take care of yourself!

[@daviddeflyer8671]

When installing our tesla charger I spent a huge amount of time trying to figure out the rules; I know this video will actually answer this to code so I'm upvoting before even watching!

[@electricalron]

Ryan, I agree 100% with you about the 55 amps allowable on the 6/2 NM. But as you know in New Jersey the DCA had a ruling that permits 6/2 for the 48 amp EV chargers. Just an FYI for any NJ licensed electricians viewing this video.

[@RyanJacksonElectrical]

Yep, and it's wrong. That's why I've had so many people from Jersey reaching out to me.

[@jmahtab]

@@kengorman4857I’m a recently licensed NJ electrician. Do you know how I can view/subscribe to this newsletter?

[@electricalron]

Well good because I have passed several installations too. @@kengorman4857

[@electricalron]

Also, we routinely do 100 amp services with #4 AWG copper SEC's. So you're saying that I need to use # 4 CU for a 60 amp circuit where the same can be used for a whole 100 amp service. That's really interesting. I'm not trying to give you a hard time just being the devil's advocate here. @@kengorman4857

[@Californians_go_home]

Ron was here !!

[@TesfayeWendwossen]

Thank 👌

[@MichaelSmith-gl4rf]

If I had a 48amp charger which requires a 60amp wire because of the 125% adjustment for the continuous load. Assuming the breaker and the charger are both rated for 75 degree I could use #6 THHN rated for 65 amps in the 75 degree column but would I be permitted to use a 50 amp double pole breaker even though I can use a 60. Also specifically how does the ground wire size change when supplying a piece of equipment for continuous load. Doe the general rule of 2 awgs smaller apply so in this case a #8 THHN would be sufficient?

[@ed6837]

Ground wire is sized buy the size of the overcurrent devise. #10 is ok up to 60 amps. Like Ryan said size the wire it needs to be a 60 amp wire so if the equipment is rated 75c #6THHN is ok. Then you calculate the breaker size which still needs to be a 60.

[@bearwires]

Exactly!

[@garbo8962]

You would think with record high copper prices two years ago EV charger manufacturers would not require a grounded conductor or four wire receptacle saving homeowners a lot of money. About 99.999% sure the power that supplies power to the full wave rectifier only uses the two energised ( 240 volt ) wires and the grounded conductor therefore never draws more then guessing 0.3 amps for supplying power to the control circuit . Even if they had to install a 60 or 80 VA 240 to 120 volt transformer inside of chargers would be a big cost savings. Always thought the NEC should have made electric cloth dryer manufacturers use a 240 volt drum motor and a small control transformer to supply less then 60 VA for 120 volt controls & a LED drum luminare thus only needing 10/2 NM cable.

[@brianapel8404]

Yes!

[@josepheskenazi2392]

Hi Ryan love all your videos and i appreciate what you do for us!! Had a quick question off the topic-- I have an L3 300KW DC Car Charging station installation which specs for input current 400 amps/Breaker size 450 amps 3 phase 480V AC. I have 120/208V 3 phase in building. My question is what size conductors can i use on the secondary side of the step up transformer? Can i decrease the size of the conductor to half (200 amp rated -3/0) because i am doubling the voltage or do i need 400 amp rated cable both on primary and secondary side of transformer? Thanx in advance

[@jmahtab]

Hi Ryan, great video as usual. Quick question, would SER fall in the 60*c column as well? I came across this when sizing for a sub panel recently. SER is printed 75*c but we’ve always treated it as NM in regard to sizing for ampacity.

[@davem5392]

SEU AND SER are generally xhhw2 or thhn/thwn. Can be used if above #10 at 90c dry location 75 wet if it’s thwn. SEU and ser do have some restrictions #10 and smaller. See 338.10

[@I_Am_Bagman]

Is it better to run THWN-2 cable vs NM? Looking to place wire before I finish up a wall for an electric car I'll purchase down the road. Trying to future proof myself. Based on my limited research, even at the same gauge, it seems to makes more sense to run thwn -2cable with a 90amp breaker. Trying to guess what will be needed in the year 2030.

[@RonFrye-pl2lz]

Note for CU conductors in NM cable.

[@grifftech]

Can I use 6 Gauge THHN on a 60A circuit breaker for the 48A EVSE?

[@dirtdevil7bo]

Anyone notice he zip tied that receptacle to his dish rack? Lol!

[@RyanJacksonElectrical]

lol it was at Home Depot or Lowe's, sometimes that's the easiest example to show the whole device. Good eye though. :D

[@kbone369]

So just limit your charger to 40A via software and your continuous load is only 40A and now you can use #6NM without issue.

[@doctorcrankenstein349]

So what happens when the "Manufacture" recommends #6 wire and a 50 amp breaker in their instructions for their 48 amp quick charge device?? Does the manufacture supersede the code? Also if the charger is direct wired does it still have to be GFI protected in a garage?

[@ssl3546]

i very much doubt the manufacturer is recommending #6 NM -- #6 THHN in conduit is fine and the preferred option.

[@doctorcrankenstein349]

never said #6 NM@@ssl3546

[@christiansantos8904]

You dont know the code, at least not in this cae. N.E.C 2023 110.3 Examination, Identification, Installation, Use, and Listing (Product Certification) of Equipment. (B) Installation and Use. "Equipment that is listed, labeled, or both, or identified for a use shall be installed and used with any instructions included in the listing, labeling, or identification."

[@rafaelvelasco6357]

Can you use power tray cable type TC-ER for 48 continues load for EV installation or possibly SE or SER?

[@nathanstebbins5400]

Oh yeah, I’d love to see the answer to this one, following

[@MrSamsamsammy]

Either one is compliant assuming all terminals are rated for 75 degree terminations. Copper 6AWG SEU is commonly used on electric 10KW air handlers with 60A OCPD’s.

[@ahahn2]

Too bad no one makes 4/2 NM cable. You end up paying for an extra wire when using NM in addition to having to size up. 6/2 MC cable or individual conductors in thinwall is the way to go.

[@silverlex1]

yup - 6g MC wire is the sweet spot.

[@timrobinson4330]

4 awg has a completely different fill/ volume calculation not like the small conductor in Mr. Jackson’s video

[@timrobinson4330]

@@silverlex1SE cable is also rated as well so long as the physical protection requirements are met

[@silverlex1]

@@timrobinson4330sure but the Tesla wall connectors aren’t rated for aluminum.

[@sparkyjerred419]

​@@silverlex1they make copper se cables.

[@silverlex1]

So So many 48A EV Chargers out there on 6G NM wire. :P

[@scotts.4471]

Just run MC cable end of story

[@silverlex1]

Yup - 6G MC is the sweet spot.

[@bobbyb2952]

Ryan, I installed a 50amp receptacle using 6-gauge NM wire. The inspector initially failed me because he said the wire was only rated 60°, and he claimed it had to be rated for 90° because “every charger I’ve ever seen requires 90°-rated conductors”. I explained that NM-B conductors do have 90° rating on their insulation and that what he was referring to only applies to some hardwired chargers. Ultimately he would only pass it if I changed the permit app to just say 50amp receptacle and remove any mention of EV Charger, which I was fine with. But shouldn’t the NEC allow 6/3 nm-b to a NEMA14-50 receptacle regardless of what it is being used for?

[@ssl3546]

That is utterly bizarre - the receptable itself does not reach 90 degrees (that would be an obvious safety hazard), you don't need to consider a rating of the utilization equipment. Moreover I doubt the receptacle was rated more than 75 degrees.

[@pauls2107]

I believe you can use 6/3 NM cable for a NEMA 14-50 but your EVSE can only draw 80% of the 50 Amps (40 Amps). This video addresses 48Amp EVSE wiring. Interestedly NJ AHJ has implied 6/3 NM is ok for a 48 Amp EVSE. They explain this in 2023 Construction Code Communicator Volume 35, Number 3 page 13. (www.nj.gov/dca/codes/publications/pdf_ccc/CCC_Fall_2023.pdf)

[@daviddeflyer8671]

The connector cord with a 14-50 plug will only pull 38 or 40 amps in this case as its (the vehicle connector) design has assumed that the circuit is a 50A non-continuous circuit and it is programmed/designed to derate as needed.

[@takearidewithme3589]

Ryan can you use 6-2 MC cable in the 75c column?

[@takearidewithme3589]

If all the terminals are rated for 75c.

[@Adventurer1]

Is this the same for MC cable?

[@JacobYoces]

So, does that mean the "next size up" rule only applies to feeders and not branch circuits? Or does that just mean the "next size up" rule doesn't apply to continuous loads?

[@RyanJacksonElectrical]

If the load calcualtion ended up requiring a 55A wire you could place it on a 60A breaker because 55A is not standard. But the load in this example was not 55A, it was 60A. So you need a minimum 60A wire, not a 55A wire.

[@GarySmith]

Good job with the AI-generated cover image...