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We are installing an EV Charger (hardwired) to our panel. I’ve had multiple electricians out for bids and have gotten differing solutions on how to proceed, so I’m hoping someone here can provide clarity.

One electrician wants to take our furnace (the first double-pole on the left side) and switch it to a 120v single-pole breaker, while also doing the same in the subpanel. Judging from the current wiring in the subpanel, only one breaker is wired currently. Doing this would allow space for a 240v 60amp double-pole that would power the EV charger.

Another electrician says we can’t change that subpanel due to NEC rules and that we’d need to rearrange elsewhere - adding a tandem somewhere else.

The furnace is relatively new and according to the manual, doesn’t need the 240v circuit breaker.

Which electrician is right here? Is this actually something easy enough that I can do myself, provided I pull the permits?Main Panel [Main][2] Subpanel

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  • I think they are both right. Most places require a furnace to be on a single circuit itself. That sub panel is wired the old way and iffy if you can add a circuit to it. Some breakers do allow two wires on a single breaker, like two light circuits might be able to go on one breaker. Read the panel labels if allowed. 60 amps for EV charger is usually more of a want than a need. You can probably be happy with less amps. It seems you have a single empty breaker that can be used for the furnace/something else.
    – crip659
    Commented Aug 31 at 17:18
  • Yikes! The furnace has no neutral! It's using ground as neutral.
    – MTA
    Commented Aug 31 at 17:34
  • How do I fix the furnace? I’m assuming you’re talking about the subpanel, correct?
    – user252712
    Commented Aug 31 at 18:39
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    @crip659 Neutral and ground must not be bonded in a subpanel. Old furnace was likely 240V-only electric resistance heat. When recently replaced with 120V unit, adding neutral was mandatory, not optional, most readily by running a new 12/2 from a new 20A breaker in space 5. The heavy cable to the subpanel is 2 conductor plus ground in a jacket. Adding a separate neutral is not code compliant. If and only if the new charger is 240V-only with no neutral required, this subpanel or an updated one can supply the charger. If the charger needs 240V with neutral, the existing cable can not be used.
    – MTA
    Commented Aug 31 at 21:31
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    @MTA The charger is already purchased. The three wires are black, green, and red - so L1, L2 and ground.
    – user252712
    Commented Sep 1 at 16:30

2 Answers 2

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To summarize the facts and recommendations from comments --

The present arrangement lacks a neutral wire for the furnace and uses ground as neutral. Bonding ground to neutral in a subpanel is against code. Using ground to serve as neutral is against code and dangerous.

You've stated that it would be easy to run a new 12/2 cable for the furnace, so I recommend you do that. Install a new 20A single pole breaker in space #5 of the main panel and either set up a new small junction box near the subpanel to power the furnace or make your connection inside the subpanel, using it only as a safe place to connect wires.

If the existing subpanel or a replacement in the same location is going to supply the EV charger with 240V, ground and no neutral, and the size of the existing 240V cable is adequate, you're almost there. Install the correct size 2-pole breakers in main panel 1 & 3 and in the subpanel if a cutoff at that location is required. It may be less expensive to use a separate cutoff with no breaker.

If the existing subpanel is not in the right location for the EV charger, you will be disconnecting, taping off, labeling and abandoning the existing heavy cable. Run your new cable (or conduit with individual wires) to the new location, install either a subpanel or a cutoff as needed for the EV charger, and connect your new cable to the correct size 2-pole breaker in 1 & 3.

Note that if it's within budget, a 3-conductor cable plus ground to the location of the EV charger will help to future-proof the install. If using a conduit and individual wires, size the conduit to accommodate a neutral wire at a future date. Your next EV charger at that location might require neutral, so try not to shortchange yourself by spending the minimum to get today's job done.

If you do run neutral to a new subpanel for the charger, then neutral and ground must remain separate there. You may have to remove a green screw in the subpanel that bonds neutral and ground. Check installation instructions.

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The furnace wiring is completely improper. This was wired as a 240V-only subpanel with no neutral, and that was fine when the furnace was straight resistance electric, but the people who replaced the furnace illegally wired their new furnace circuit like this because they're not electricians.

So the first step here is a new homerun from the main panel to the furnace area. Splices allowed if they remain accessible.

Now you have a 3-wire, 240V-only, hot-hot-ground subpanel. You can put EV charging in there as long as it is a hardwired connection or a NEMA 6-xx socket connection. Do not power a NEMA 14-30 or 14-50 socket out of this panel.

I suspect with that much electric heat removed from the house, you are fine on the overall load calculation. Still, consider that, and also Technology Connections' sage advice on sensible charge rates. https://www.youtube.com/watch?v=Iyp_X3mwE1w&t=1695s

The "headaches you hadn't bargained for" are largely things catching on fire. Which happens vastly more on 32-48A EV setups than 12-24A.

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