Panel upgrade for electric car charging


Old 09-11-16, 12:23 PM
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Panel upgrade for electric car charging

I need to upgrade my garage sub-panel to 100 or 150 amp (from 50) to accommodate charging an electric car I'm getting soon. Currently my sub-panel has your typical stuff plus a shop heater 240 volt hookup (6K watt shop heater on a 35 amp breaker).

I have two options on the car charging- one is a 50 amp and one is 100 amp breaker (actual charge rates I think are like 40 and 80 amps respectively). I'd like the latter, but am concerned it would also then require a main-panel upgrade from my existing 200 amp service.

I'm perfectly comfortable upgrading the sub-panel (though have never tried upgrading to something like a 150 amp sub-panel, which may be required if charging the car and running the shop heater at the same time), but have never upgraded a main service.

So I'm currently just kind of debating whether I should just go with the 40 amp car charging, which would only require upgrading my sub-panel to 100 amps, then I'd be good everywhere I *think* and that's something I can easily do myself.

Or going with the 80 amp charging, which I *think* would require upgrading my main service to like 300 amps or something from 200 amps, and I'm not fully confident at this stage I'd want to do that one myself, which would mean a pretty sharp increase in cost.

Alternatively I could potentially just ditch my shop heater and then I *think* I'd be good doing just the 100 amp sub-panel upgrade to the garage and leaving the main panel otherwise as-is.

Here's my current main panel. Thoughts?

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Old 09-11-16, 01:08 PM
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Is this a detached garage? If it is an attached garage than running a line from the main panel for the charger may be a better solution.
Old 09-11-16, 02:12 PM
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Detached, though it's only about 20 ft from the main panel to where the car will plugin in the garage and technically it is attached via a covered walkway, but I suspect that's still considered detached. My main panel is full though anyway and I don't "think" can accommodate anymore slim breakers.
Old 09-11-16, 04:01 PM
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The garage 50 amp breaker would be removed and a 100 installed in its place. The existing 50 amp feeder will need to be removed or abandoned in place.

The 50 you have now appears to be a GFCI breaker which you would not need if the receptacles (120 volt, 15/20 amp) in the garage are protected by some other manner. This can be breakers in the new panel, or just GFCI devices in the first device box.

While I doubt you will need to upgrade your existing main panel you do have A LOT of electric equipment. I see a range, dryer, 2 - 60 amp circuits for heat strips (I assume), and a water heater. I would recommend you do a load calculation. Google "load calculation" to find an easy calculator.
Old 09-13-16, 06:39 PM
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2 - 60 amp circuits for heat strips (I assume),
I'm guessing that is a 2-circuit 20 KW furnace. I agree, you need to do a load calculation. The existing load and extra capacity for 80 more amps is marginal at best.
Old 09-14-16, 10:08 AM
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Even though you can proactively manage your power use to avoid an overload using your car charger, the load calculation results will tell you whether you need to upgrade the main panel (and perhaps the electrical service and meter). Your city code might require all that.
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