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I live in a shared condo where two units share an electrical panel in an electrical closet behind the garage. I'm thinking of buying (well, leasing) an electric car and in order to charge it, would like to install a 30A 240VAC Level 2 charger (which requires a 40A breaker).

Before I pay an electrician to come out to do a site survey, I wanted to see if what I had in mind is even possible given the panel that I have now.

It's a shared panel with 2 meters, each unit has a 100A main breaker (under the plastic cover below the meters), but there are no other breakers or slots in the panel that I'm aware of. The meters and disconnect breaker for each unit on on the right-hand side of the panel, the cover on the left side of the panel is sealed with a tamper-proof seal with a tag from my local electrical inspector so I don't know what's inside.

My dwelling's electrical service runs about 40 feet underground to the kitchen in the middle of my unit, so I don't think that adding a circuit on my main panel and pulling it out to the garage is feasible. It's a straight shot about 20 feet from the electrical wiring closet to the garage wall where I'd want the charger so it'd be a pretty easy cabling run.

Since there don't seem to be any open breaker slots, it doesn't look like I can just pop in a 40A breaker in that main panel and run a circuit to the garage. But I was thinking that I may be able to:

  • Put a subpanel with a 40A breaker next to the main panel and somehow tap into the feed coming off the 100A breaker inside the main panel to feed that subpanel, then run suitable wiring from the subpanel to the charger. However, the subpanel may have clearance issues, it looks like there's room in the closet to mount it to the left of the main panel, but it wouldn't be in front of the door and would only have around 18" of clearance in front of it so that may not be sufficient.
  • If a subpanel in the closet won't work, then I was thinking that maybe I could tap into the 100A circuit and run 100A wiring to a subpanel in the garage with a 40A breaker for the charger.

(and when I say "I", I mean a licensed electrician, since this is not something I'd do myself, and it will have to be done under permit with approval by my HOA).

Does this sound at all feasible? I guess my biggest question is whether or not it's possible to tap into the feed coming off of my 100A breaker -- I'm guessing that there's no convenient bus bar to screw new wires into so I'm envisioning some sort of big pigtail with split-bolt connectors?

Is there anything else I need to consider? The 1000 sq ft house has gas heat and appliances and no air conditioning, so I don't think a 30A charger will push me over the safe loading for my 100A service.

Also as a part of this work, I'd like to run a 20A 120VAC utility outlet so I can plug in a vacuum cleaner or something, but I'm assuming that will be a relatively easy piece of this project.

Here's a picture of the panel:

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And a closeup of the label on the left-side panel:

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  • You cannot legally open that box; the contents inside are owned by your utility. You need to talk to your utility. (That's why there's the red tamper-evident flag on it)
    – Billy ONeal
    Commented Aug 5, 2015 at 17:55
  • The red tag is from my local county inspector, not the utility. The only seals that are obviously owned by the utility are the plastic ones on the meters, though I don't know who owns the little metal tamper-proof seals on the box on the left. In any case, I'm not going to open anything up myself, just want to know if what I want to do sounds feasible before I spend money on more research.
    – Johnny
    Commented Aug 5, 2015 at 18:07
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    I think it's unlikely you'd be able to add breakers for user circuits in the existing meter boxes. I think you best bet is to add a new (small) 100A panel out there and make your existing in-unit panel a sub to that. Presumably there is a disconnect at the meter which makes your in-unit panel effectively a sub anyway with isolated ground and neutral buses. Having said this, I have no idea if there's room there for such a panel or if there are any other factors that would make this a problem.
    – DoxyLover
    Commented Aug 5, 2015 at 18:21

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To answer your biggest question: I'm pretty sure it's not code-legal to tap into the feed from your meter panel with split-bolt connections. It's possible that your breaker panel has some lugs near the bottom of the load side bus bars to connect a feed to a subpanel, but most don't.

So a possible solution is what Doxy suggests: a new 100A panel that feeds your existing panel as a sub-panel. Before you consider that, I'd check to see if your panel type admits half-size tandem breakers. These are breakers that fit two half-size breakers into the space for one normal breaker, and this would free enough space for a 40A breaker to your EV charging circuit in the garage.

Another possible difficulty, though, is that your 100A service is awfully marginal for the addition for a 40A EV charging circuit. Although you didn't give all the relevant details, I assume your 1000 sq ft house (does this include the basement, if there is one?) has an electric dryer. In my jurisdiction, a load calculation shows you would require a 107A service. You may be able to get away with a 100A service, but it will depend on your inspector/permitting authority.

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