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I have an existing 50A circuit for an induction cooktop wired with 6/3 stranded Romex. It runs through the finished basement ceiling bulkhead and at some point near a rim joist where it feeds to 1st level kitchen. I am thinking of adding a junction box to feed a second 14-50R in the garage (1st level).

The j-box will be recessed and it's on the hidden side of the bulkhead anyway so visually it's a perfect spot. I am thinking of running a 6/3 wire from here, through the plate in the rim-joist and out to the other side of the (attached) garage wall.

The charge will be limited to 32 amp draw (14-50P). I will not be using both circuits at the same time as EV charge will be a scheduled one only at night/early morning hours. The cooktop is a multi-zone and specifies 12,000W (50a circuit). The maximum a single zone can draw in boost mode is 3,600W (15A).

Would branching out this circuit be to the code (KY USA)? And if so, what kind of box, and splicing hardware will I need? Other option is to run a whole new circuitry from the primary panel to a new garage sub-panel but at the moment I have no need, and the run from this projected J-box is only a few feet, which saves on cabling. Anything else I need to be watching out for as far as going through the interior wall to the attached garage? Presumably, that's an insulated wall.

Thanks! enter image description here

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    A junction box cannot be behind drywall, can be behind a access door. I think you would need a device that shares the circuit by cutting off the EV when the stove is on. Been some talk on here about them. Depending on your location, a receptacle in a garage must be on/protected by a GFCI(that size means a breaker). Usually recommended to hardwire the EV charger, not use a plug.
    – crip659
    Oct 26, 2023 at 16:10
  • It won't be behind drywall. It will be recessed with the plate cover flash with drywall. I am familiar with power-sharing devices but they are nearly $700 so I am looking for a lower cost code-compliant way. 32A EV charger doesn't require hardwiring and the one that came wih my vehicle is a portable with 14-50P that cannot be hardwired but draws 32A max.
    – David
    Oct 26, 2023 at 16:19
  • The lower cost code compliant method is to use an existing circuit that is in the garage, like a regular wall outlet with a granny cord. Properly installing higher power EV charging requires either a dedicated outlet with a GFCI on a new circuit, or a hardwired circuit of the appropriate size for the EVSE.
    – KMJ
    Oct 26, 2023 at 17:00
  • IDK if this is of any use to you: diy.stackexchange.com/questions/136377/…
    – Huesmann
    Oct 26, 2023 at 22:45

2 Answers 2

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Every EV novice seems to inherit the exact same pack of misconceptions about home charging, largely fueled by the dubious economy of using the travel unit as the daily home charger. I get you may be at sixes and sevens about the whole "EV thing" and are poised to return the EV to the lessor if it doesn't work out for you, so you want to make bare minimum investment in infrastructure. But you're mistaken. EVs are here to stay and it's silly to scrimp only to have a worse overall experience.

I will not be using both circuits at the same time as EV charge will be a scheduled one only at night/early morning hours.

It's one circuit. But the thing you're trying to do isn't allowed. That circuit is dedicated to range/oven per NEC 220.55. The EVSE requires a dedicated circuit per 625.40.

Generally, the idea of a "pinky promise" to be careful not to operate conflicting things at once is not recognized in NEC - e.g. the requirement for a generator interlock.

I am familiar with power-sharing devices but they are nearly $700 so I am looking for a lower cost code-compliant way.

Alright. See where you plan to put that box? Stick a Siemens 8-space subpanel instead. ($55) (does not work with a 4-space due to Siemens oddities with breaker spacing).

Two 50A breakers ($15 and $83 per you) in the subpanel with an $30 ECSBPK02 interlock between them. I'm picking Siemens brand because the ECSPBK01 interlock makes this easy. You can do the same thing with Square QO2DTI or Eaton CHML, but CH and QO panel lines are not cheap, and cheap is a parameter here.

You'll have to switch it manually but it's code legal. Hey, you wanted the cheapest rig possible. This is it.

I can purchase a 50A GFCI Siemens breaker for $83 - not a big deal.

Because your panel is Siemens legacy? Breakers don't cross-fit, even though they seem to.

The EVSE breaker will need to be GFCI, which is unfortunate, because it brings nothing to EV charging. But hey, you wanted the socket.

Oh, and long experience of the EV community is that the Leviton, Legrand and Eaton sockets (all the cheapies) tend to melt down under EV loads. the community universally recommends the $80-ish Hubbell or Bryant.

I am looking for a lower cost

One of my frustrations with the "money-scrimping" philosophy is that it seems to save so little. subpanels, Hubbell sockets, GFCI breakers... doesn't sound great.

I would run a plain, $15, 240V/20A breaker using 12/2 Romex (or whatever I had lying around) -- hardwired to a $450 Wallbox (CostCo). Yes, it's more. But not a lot more, and it will improve the experience all around. When nightly charging is easier, you'll charge nightly. Untangling that travel unit is a drag, and that encourages less frequent charging (which requires larger circuit).

4kW charge rate (20A circuit @ 240V) is plenty for home charging, and will provide 100-150 miles a night depending on the car and the night. Feel free to use fatter wire if your panel's Load Calc can support it.

And, because it's a Wallbox, I can add-on EVEMS load management, solar capture to export into the car rather than to the utility, or Power Sharing among multiple EVs.

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  • Great answer, and no, I am not trying to cheap out. Was just seeing if existing circuit can be used to the code as this was the easiest. If I am going the sub-panel route, will be running a 90A or a 125A circuit. I have an electrician who would do load calc and final connections/torquing but I am researching what I need so that I can do most of the wiring work. If I go this route, 1/0 AL SAE with 125A breaker protected sub-panel is what I am thinking. Just need to figure out a proper way to breach the firewall between garage and interior. Any tips? Will be coming up rim joist & out to garage
    – David
    Oct 27, 2023 at 13:11
  • One other thing, I see that KY USA hasn't adopted the 2020 NEC code. As I understand the GFCI requirement came with that year's changes. Am I mistaken? nfpa.org/NEC/NEC-adoption-and-use/NEC-adoption-maps
    – David
    Oct 27, 2023 at 13:27
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There are a bunch of other issues - how do you safely manage the load (what about the night before Thanksgiving when you decide to cook a bunch of stuff while the car is charging), EVSE ("charger") should really be hardwired rather than plug-in, you don't actually need 50A for charging in most cases, etc.

But the biggest issue is that an electric cooktop normally requires a dedicated circuit. If it is hardwired then it has to be dedicated anyway (can't have receptacles on a circuit with > 50% of capacity used by hardwired equipment) but even with a plug/receptacle connection this is not allowed.

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    Likewise, using a receptacle in the garage then requires GFCI protection (which using the EVSE would avoid.) That's an expensive breaker, on top of the other issues you mention.
    – Ecnerwal
    Oct 26, 2023 at 16:17
  • It may or may not require GFCI, as 240V GFCI is a relatively new requirement so it depends on local NEC year. Oct 26, 2023 at 16:19
  • 32A EV charger doesn't require hardwiring and the one that came with my vehicle is a portable with 14-50P that cannot be hardwired but draws 32A max. I can purchase a 50A GFCI Siemens breaker for $83 - not a big deal. So sounds like your second paragraph makes it a hard "no". Do yo mind citing the code?
    – David
    Oct 26, 2023 at 16:27
  • I don't mind citing the code. Just haven't found it yet and don't have time to search more right now. But I'm pretty sure of it. If Harper doesn't add a lengthy answer (or just a code citation) by the time I have a chance later, I'll look for it. Oct 26, 2023 at 16:29
  • @manassehkatz-Moving2Codidact as far as Thanksgiving, in the rare cases where both circuits are used AND maxed to 50A, wouldn't the main breaker provide the protection? I can disconnect the EV and keep cooking happily
    – David
    Oct 26, 2023 at 16:34

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