9

I'm adding a circuit to my garage for an EV charger. Yes, I have pulled a permit. I live in Massachusetts.

Here's my plan:

I'll be adding a new 60 amp GFCI breaker to the panel. Yes, there is space in the panel. The GFCI is required because the new circuit is in the garage (210.8.A). The nominal load of the charger is 50 amps so 60 amp is appropriate.

Said panel is in the basement, diagonally below the garage. I plan on running the wires exposed up the basement wall, then over along the ceiling to below the basement floor. I'll add a small hole (meeting (304.A.1)) into the floor of the garage. The wires will run on through the hole, up the wall of the garage, along the ceiling, then down a post in the center of the garage. Since the garage space would expose the wires to physical damage (300.4), I will need to protect the wires with conduit.

For this, I'll be using steel EMT which satisfies this requirement (358.E). (I wanted to use schedule 80 PVC but the big box stores are out of stock).

The charger I'm installing can draw as much as 50 amps and calls for a conductor compatible with 90C. In order to satisfy the 1.25x requirement for constant loads ( 215.2.A.1 ), the wire should be rated for 62.5 amps. I'll be using THHN AWG 6 copper which is rated to 65 amps and 90C (B.2(1)). Total wire distance is less than 35 ft.

Questions I don't have answers to:

  • My charger only uses the two hot lines plus a neutral. What gauge does the neutral need to be? Citing the code for an answer would be appreciated.

  • I will be direct wiring the charger. The hole for direct wiring is on the bottom of the charger while the wires will be coming from above. Is there an elegant way for the wires to do a 180 degree turn?

  • I've read that water can condense on the inside of the EMT conduit. This can be addressed by adding weeping holes along the conduit. Should I be worried about this / address this?

  • Are there requirements about the hole between the basement and garage besides size (304.A.1)?

products I'm using:

charger

GFCI breaker

wire

the post

enter image description here

11
  • 5
    Quite sure the charger uses ground and not neutral. Do you need 50amp charger, do a lot of daily driving, or is it more of a want because it is big? Panel might have open space, but have you done a load calculation yet to see how much extra power/amps are available? Hard wiring the charger instead of a plug in, you usually do not need GFCI breaker. Can save some money there.
    – crip659
    Commented Feb 18 at 15:59
  • 5
    For someone who knows nothing, your question is well informed. So let me put it differently -- you can't run THHN except in conduit. Given the size of the cable, it won't be any easier to run cable than conduit, I think you should just run conduit end to end. If there are a lot of turns you'll need a lot of pull points. For the last one, a 180, a junction box below the charger may be a good idea (instead of 2 90s) but I'd like to see the pole. A photo of the pole and the charger would help. There are ways.
    – jay613
    Commented Feb 18 at 16:16
  • 3
    What is the total wire distance? I do not recommend designing something that operates at 90C (194F). The reason the wire is so hot is resistance which also results in voltage drop. Wire is expensive but I always choose the next larger wire size to reduce temperature and voltage drop. The answer by @manassehkatz-moving-2-codidact is excellent and I would chose the subpanel route that he recommends. Commented Feb 18 at 17:16
  • 3
    Required reading for EV charger installs
    – FreeMan
    Commented Feb 18 at 21:43
  • 1
    1) You say there's space in the panel for the breaker, but is there room in your load calculation to draw an extra 60 amps? 2) Most electrical supply places will sell direct to consumers, not just electricians - check them for your Sch 80. Probably cheaper there. 3) EMT will serve as your ground, so what you spend on that will be offset by not having to buy a 3rd or 4th wire for grounding. 3) Your "charger" link is to a google search, please edit to link directly to the product so we don't have to guess and aren't all tracked by google.
    – FreeMan
    Commented Feb 18 at 21:49

3 Answers 3

18

I'll be adding a new 60amp gfci breaker to the panel.

I will be direct wiring the charger.

STOP!

These two statements are in conflict.

If you hardwire a charger then you do NOT need a GFCI/breaker. If you install a receptacle for a plug-in charger then you do need a GFCI/breaker.

Hardwire is the preferred way to do this, and one of the reasons is because it removes the need for the GFCI/breaker.

Now let's get on to the sizing.

As you have discovered, 50A actual requires a 62.5A circuit. That means 65A-rated (60 C column cable or 75 C column wire) and general recommendation is either 6 AWG copper wire (not cable) or 4 AWG aluminum wire. Many chargers do not work with aluminum wire - check the specs to find out.

But that is on the order of double what you actually need. 20A (16A actual) or 30A (24A actual) is enough for most people, most of the time, unless they plan on two vehicles charging at the same time.

I would recommend one of two options:

  • Subpanel

Instead of running a 65A circuit directly to the EVSE, run a 65A (or perhaps 70A or even 90A, depending on load capacity) circuit to a subpanel in the garage. This subpanel might start out with just a 30A circuit for one EVSE (or perhaps a little larger, but do NOT put in a single EVSE at 50A/62.5A - that's just crazy and leaves you no room for anything else.) This has some key advantages over a single circuit: You can use aluminum wire between subpanels and then just short copper wire from the subpanel to the EVSE. You can add a second EVSE later on with just short wires to the new subpanel. You can add other circuits - lighting, tools, etc. to the subpanel.

  • Single Circuit - 30A

Keep it small and therefore relatively inexpensive. In fact, if you limit it to 30A, which is more than enough for most vehicles charging overnight based on typical (and even a bit extra) usage, then you can use much more common (and much less expensive) 10 AWG/30A NM cable rather than going with conduit and wires. (Unless there is an outside = wet location component involved.)

Wires vs. Cables

Wires need protection all the time. Any place they are outside of a panel or junction box they need to be in conduit.

Cables only need protection where subject to damage. Typically this means exposed on walls but not inside walls (behind drywall) and not when above 8' (e.g., open ceiling). This protection can be large conduit or it can be a strip of metal or wood covering the cable.

Pick one or the other. If you are going outside then you have to go with wires/conduit. If you are inside then cables are fine (except where not allowed at all - e.g., Chicago).

What you really want to avoid, particularly when using large wires (e.g., for 65A) is connections. With 10 AWG 30A wire and cables, transitions are simple wire nuts. With 6 AWG, 4 AWG, etc. connections between wires requires Polaris or other special connectors which cost more and require more space to install. Plus transitioning between copper and aluminum is problematic. So pick something:

  • Cable vs. wire based on pricing (cables are more expensive than individual wires but you have to add the cost of conduit) and installation work.
  • Copper vs. aluminum based on devices being connected. Breakers can normally handle copper or aluminum. Many devices such as EVSE can only handle copper.

Neutral and Ground

If you install a subpanel, neutral (except at very large sizes) is the same size as the hot wires. From the subpanel to the EVSE no neutral.

If you install an individual circuit, no neutral. But if you do this and use conduit and small wires (e.g., 10 AWG 30A) to save money, I would size the conduit such that it could handle much larger wires for a subpanel in the future, including a neutral wire. Installation work will be the same, conduit cost will be higher but you will be future-proof.

Ground wire size is a little more complicated. According to this ground wire chart for a circuit (or subpanel) up to 60A, 10 AWG copper or 8 AWG aluminum. For a circuit (or subpanel) larger than 60A, up to 100A, 8 AWG copper or 6 AWG aluminum.

Wet Inside Conduit

Any conduit outdoors is presumed to fill with water. Weep holes in conduit bodies or junction boxes are a good idea. I recently saw an NEC update regarding sizing of those holes (if not provided by the manufacturer), essentially formalizing a common practice. If everything is inside conditioned space (garages vary quite a bit) then there may never be any water. YMMV. But if you use wires that are designed so that they can be in water (THWN vs. THHN) then there is no problem.

Load Calculation

You can't just "add big stuff everywhere". If you could do that, everyone could have tankless electric hot water heating, resistance electric heating and 50A EV charging without worrying about their electric supply. But it doesn't work that way.

While it does get complicated, there is a formal NEC Load Calculation procedure to determine how much power your home requires. It incorporates many different things, including:

  • Size (square feet) of the building
  • Required dedicated circuits (kitchen, bathroom)
  • Large appliances such as water heater
  • EV charging
  • HVAC (larger of H or C)
  • Cooking (special rules apply, so not as bad as you might think)

You do this calculation for your entire house (utility service). That tells you how much room you have to add more things, such as EV charging. If you have enough room, great. If you don't then you can scale back (e.g., 30A instead of 62.5A for charging), change some things (e.g., heat pump instead of resistance heat) or do something to shed loads automatically.

In addition to your entire service, you really need a Load Calculation at each level. In this case, that means the subpanel that will be feeding the EVSE (or feeding a garage subpanel). If you have 200A total with 120A in use then you have 80A available. But if the subpanel you want to use is only being fed 100A and is already using 40A then you only have 60A to send to the garage. The details can vary quite a bit and you may have a major problem (unable to even dedicate 20A to charging) or you may have no problem at all. But you need to find out before you start installing things.

10
  • Can you cite the hardwired == no need for gfci? The town wiring inspector said this was necessary but it's possible he believed I was installing a receptacle. As for the amps, I've sized this for our worst case situation. So I'm proceeding with the 50 amp nominal charger. I hadn't thought of adding a sub panel but I don't think it would make sense. The main panel is already very close to the garage - it'll only take 5' of wire to get from the main panel to the garage floor.
    – holmeski
    Commented Feb 18 at 17:13
  • 8
    625.54 refers specifically to receptacles - hardwired doesn't need. The ChargePoint web page dances around this by indicating in multiple places that where code requires GFCI/breaker you should do hardwired instead of receptacle but doesn't actually say "the reason you should hardwire is so that you don't need GFCI/breaker because GFCI/breaker would mess things up". Talk to your inspector and specifically say "I am installing a hardwired EVSE with no plug-in receptacle on the circuit, do I need GFCI/breaker?" and if they say "Yes" then ask them for a code citation. Commented Feb 18 at 17:21
  • 1
    Not sure exactly what the question is about the hole. If you use individual wires then that hole has to have conduit inside it and the wires inside the conduit. If you use a cable then you just run it through the hole. Commented Feb 18 at 19:00
  • 1
    If you use EMT, the conduit itself can be (if properly bonded at each end) the ground conductor, so you'll only need 2 wires (hot, hot) to a JB or 3 wires (hot, hot, neutral) to a subpanel.
    – FreeMan
    Commented Feb 18 at 21:52
  • 4
    @JimStewart I imagine that is possible. But the need for GFCI somewhere is huge - think about it - car just came in wet from a rainy trip, people moving around garage, etc. I think GFCI is a really, really good idea here. But the key is that it is provided - by design - in the EVSE instead of the breaker. Once you already have GFCI, you do not want a second one because then you end up on a crazy trip. Commented Feb 18 at 21:52
9

I'll be adding a new 60amp GFCI breaker to the panel.

OK, first let's hit the regenerative brakes on that charge speed. That is a BONKERS charge speed for home charging. First, I advise reviewing Technology Connections' very common-sense video about home charging, and if you want the part about sizing level 2 circuits, that's at 28:15.

https://www.youtube.com/watch?v=Iyp_X3mwE1w&t=1695s

Now, if you want to slap a new 60A load onto your panel, unless you cheat (more on that later) you need to have the service capacity needed for the job. That is determined by your AHJ, but most want you on NEC 220.82, this worksheet here. Note line 2 applies only to your 2-3 kitchen general-use receptacle circuits, not other rooms and not circuits dedicated to dishwasher, disposal, microwave etc.

Now, if you've tempered your requirements per Alec's video, and you still don't have room for your EV capacity per your Load Calculation, then back goes that Chargepoint and get one of the few stations capable of EVEMS, which auto-adjusts EV charge rate on the fly to protect the panel from overload. Some vendors' EVEMS can also do solar capture, or direct to the car exactly the solar power you'd otherwise be exporting to the utility.

The other thing about wiring is that lots of people (to save a measly $30) want to run wires at their absolute thermal limit. EV charging is the most brutal load a house will ever see. Especially if someone operates in gas station mode and doesn't recharge til near empty, resulting in a many-hours-long session where thermal rise can really overcome thermal mass. So running a wire right up at thermal limits is not something I recommend. Such hot running wires tends to uncover every flaw in an installation and make it crispy. Now were you planning to use a torque screwdriver per 110.14? Case in point on those "flaws".

The GFCI is required because the new circuit is in the garage (210.8.A).

It does not say "breaker". The GFCI protection can be provided by a GFCI receptacle. And happily, if you look into what an EVSE ("charger" but not) actually is, It Is A GFCI Receptacle... really.

"How can it possibly be a receptacle? It has a cord on it!" Not necessarily. The new J3400 standard specifically authorizes untethered stations, with a J3068 socket on the wall instead of a cord. You cannot possibly deny a box with a socket is a receptacle. OK, so adding a cord changes nothing to the equation. It's still a receptacle.

The nominal load of the charger is 50amps so 60 amp is appropriate.

No it isn't. 50A EV charge rate requires a bunch of things. First the circuit must be 62.5A because of the 125% rule in 625.42. Second, because the circuit is now over 60A, a disconnect switch at the station is now required per 625.43.

Clearly, a "ChargePointy-Haired Boss" told the engineers (in Cave Johnson style) "I want a 50A station! 2 amps more than the other guys." The engineers facepalmed and said "But no car on the market can usefully use that. They all stop at 48 amps, except for a few larger vehicles which go all the way to 80 amps (and for them, stopping at 50A is silly, and you might as well go to 80A). Also, that will kick in the disconnect rule per 625.43." Anyway, cPHB won that argument, so we have this weird wart of a product obliging us to explain all this stuff to people.

I'm ignoring the part where GFCI breakers over 60A are unobtanium, because you don't need a GFCI for a hardwired unit.

(I wanted to use schedule 80 PVC but the big box stores are out of stock).

IME big-box stores don't sell sched 80. I'm a bigger fan of EMT anyway since it's not glued, so easier to correct defects.

The charger I'm installing can draw as much as 50 amps and calls for a conductor compatible with 90C.

They are saying their terminals are rated 90C. This is relevant to 110.14(B) but is not relevant to anything in a dwelling, as panels are not rated 90C, and limit you to the 75 number in any case. The 90C columns in table 310.16 may as well not exist.

Ill be using THHN AWG 6 copper which is rated to 65 amps and 90C (B.2(1)). Total wire distance is less than 35ft.

WHAT??????? You just said you were only using conduit as a damage shield to run up the wall. You didn't say anything about running conduit the entire way box to box. You can't run THHN wire not in a conduit.

If you don't want to run in a conduit, you have to use cable. If you need 75C rated cable, look at SER or MC (or SEU if you can find it).

Question 1: My charger only uses the two hot lines plus a neutral. What gauge does the neutral need to be? Citing the code for an answer would be appreciated.

Wow, novice. All your code cites don't reflect any real knowledge, eh? Yeah, these huge "swiss cheese" knowledge gaps really show what happens when someone tries to plink knowledge off a search engine or AI. The thing only answers questions, it doesn't tell you which questions to ask. NEC itself says that in 90.1: "Not intended as an instruction manual for untrained persons". Please get a book or courseware which is intended for that. Everyone needs a well-rounded primer on the subject, so they know which questions to ask.

Anyway to your question, a) No EV uses neutral, see J1772 and Tesla port spec. And b) No EVSE needs neutral, see NEC 110.3(B).

I will be direct wiring the charger. The hole for direct wiring is on the bottom of the charger while the wires will be coming from above. Is there an elegant way for the wires to do a 180deg turn?

NEC 110.3(B) read the installation instructions. Many stations accept top entry, I would just get one that does. The Chargepoint is kind of a dopey unit, as you can tell from the lack of EVEMS, the 50A limit and the fact they had to introduce a whole new model (the Flex) just to provide adjustable amp rate. And many of us are very suspicious of their aspirations to product-ize and monetize their users. ChargePoint wants "charging as a service". If you have some weird thing where you want that, ask for better options.

I've read that water can condense on the inside of the EMT conduit. This can be addressed by adding weeping holes along the conduit. Should I be worried about this / address this?

That's only a problem if it goes outdoors.

8
  • I had assumed that the 1.25x was only for wire size to handle heat issues. Are you saying I need a breaker that can handle 62.5 amps?
    – holmeski
    Commented Feb 18 at 23:47
  • Where in the code does it say thhn needs to be in conduit? ( I believe you but I looked and have missed it)
    – holmeski
    Commented Feb 18 at 23:48
  • @holmeski -- NEC 300.3(A) is what you're after, although the Code is a bit oblique about how it says that (as it needs to accommodate things like legacy K&T still) Commented Feb 19 at 0:25
  • 1.25x is to handle heat issues, and other reasons too. But here's the deal: power-required x 1.25 = power-to-be- provisioned. In other words, size of the circuit. Which means: Circuit breaker at least 62.5 and wire to match. Nearest breaker size is 65A (or if not available for a particular panel then 70A). You are technically obligated to have wire to match the circuit size even if the breaker is over due to availability. And wire sizes are only in specific increments as well. So end result is 65A wire (there is no 62.5A wire) and a circuit breaker either 65A or 70A. (But not Commented Feb 19 at 1:52
  • 2
    @manassehkatz 65A should be alright on #6 75°C wire... the issue is the manual itself calls out a 70A circuit in that case, so deeper and deeper we go. Bottom line the Chargepoint ain't a great unit. At least the Flex can be set to 48A or less, unlike the earlier model. Commented Feb 19 at 2:46
-2

You only need the two line wires and at least a 10 gauge ground wire. Neutral is just a waste of copper and money unless you're going to use a 14-50R and use a plug on the EVSE or want to future proof the pull.

The ground fault breaker is overkill, the EVSE has its own ground fault capabilities. If it is wall mounted and always plugged in, its fine. If you want to argue this point, how many RV receptacles have GFI or even require it? I live in Indiana, so your code requirements may vary. I installed a 100A circuit for an 80A EVSE last August and it is working great. 19kW home charging is amazing!

Generally if you want to pull 50A continuous, your breaker should be sized to 125% of that. 60A, 120% is close enough. If you keep space above this breaker, it will be completely fine. The derating is for a filled load center as the breakers are rated for use in open air for some dumb reason or another.

8
  • While none of this is wrong, it duplicates information in the other two answers and doesn't really add anything new
    – FreeMan
    Commented Feb 19 at 19:30
  • 1
    If you'll take the tour, you'll get a feel for how this place works. There's a ban on commenting on other peoples Q&A until you reach 50 rep. I get it (prevents spam - sorta), but it's frustrating, too. I've flagged this, maybe a mod will convert it to a comment for you...
    – FreeMan
    Commented Feb 19 at 19:41
  • 1
    I actually think my comment adds new, since everyone else is saying explicitly he cannot do this and that. But he can and it is okay. Math says so. My experience here doubts 2.5 amps is a cause for concern, but that dude thinks stuff is melting down if that 2.5 amps is accommodated. Thats simply not the case. 60A breaker is fine for 50A. Commented Feb 19 at 19:54
  • 1
    Are you saying NEC 210.19(A)(1)(a) is just a suggestion that you don't need to follow? And would the inspector agree?
    – Rick
    Commented Feb 19 at 20:47
  • 2
    Edit your profile so we can see your qualifications. That will help in determining how qualified you are to provide an answer. For example, I do not have a high profile here, but I do on other Stack Exchange sites. That helps to determine the quality of my answers. Try not to argue with others. If you are right, you are right and most of us will either know that or how to look it up. The problem that I have with your answer is you are expressing your opinions instead of stating facts and citations. The point that it works for you is not relevant in the world of codes and standards. Commented Feb 19 at 20:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.