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I want to wire a dedicated plugin to the front of my garage for a new EV, which at the moment needs to be 120. But later, I may upgrade to a 240 based charger.

Is there a suggested way I could wire this up to give myself flexibility in the future to convert to 240 without running new wire? Like run 3 (hot -hot - ground) and just use one hot for now, and the second later for 220?

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Run all four wires

Run a /3 cable (hot, hot, neutral, ground) to the receptacle location. For 110, you cap off a hot, and use the other hot, the neutral, and the ground for the receptacle. For 220, you can cap off the neutral and have 2 hots and a ground for a NEMA 6. If you want 110 & 220 together at some point, you can then land all four wires on a NEMA 14.

I'd run this circuit using 6/3 by the way -- that allows you to have anything up to a NEMA 14-50 there with an appropriate breaker to match.

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  • 14-50 would make sense. I also have noticed that there are 220 to 110 adapters (like amazon.com/AC-WORKS-AD1430520-Household-Connector/dp/B0778XN2Q7/…) - so I could wire up for 220 and use one of them in the mean time. – Tim Holt Dec 24 '17 at 5:14
  • @TimHolt -- I'd pigtail in the 110 receptacle for now and put the right-sized breaker for the receptacle you use in. The wire can be fatter without an issue (you'll just need pigtails to attach a 15 or 20A receptacle to the fat wires) – ThreePhaseEel Dec 24 '17 at 5:16
  • @TimHolt You will find that cheater block is not UL listed... or if listed, the listing is a forgery. Dodgy places like eBay, AliBaba and Amazon Marketplace will happily sell you anything, legal, safe or not. – Harper - Reinstate Monica Dec 24 '17 at 6:04
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    @TimHolt For the most flexibility I would install a subpanel. – Retired Master Electrician Dec 24 '17 at 15:43
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There are three possible wiring modes in North American split-phase wiring:

  • 120V only: One hot, neutral, and ground. (/2 plus ground)
  • 240V only: one hot, the other hot, and ground, no neutral. (/2 plus ground)
  • 240V/120V: both hots, and neutral, and ground. (/3 plus ground)

Note the same /2 cable is used in both of the first examples. Just the white wire is marked with tape to mark it as a "hot", and the wires are landed on a 240V breaker not a 120V. So if you are 100% confident that your future 240V chargers will be 240V-only, you could get away with /2 cable.

Unfortunately I am aware that some chargers are not. I don't know what's wrong with those builders, the bits they need 120V for could easily be made to work on 240V, and then the charger could be marketed worldwide. SMH...

But there's another way

You could bring out 6/3 cable out to a subpanel, giving you 240/120V split at the subpanel. Very standard stuff. Then, add a breaker and receptacle for whcihever charger you get, when you get it. The general idea is, you're only going to be charging one EV at a time. So if you have a 30A charger and a 50A charger, you only need to provision 50A of service, not 80A.

The same logic applies when bringing power out to a single RV parking/camp site. You can provision all of 240/50, 240/30, 120/30 and 120/20, knowing that an RV will only use one of them at a time.

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  • Can you give us full electrical specifications on both of the units considered? I think that some of the options listed above could involve considerable unnecessary expense. – Paul Logan Dec 24 '17 at 22:58
  • @PaulLogan How can the person provide "full electrical specifications" for a future charger that may not even exist yet? Of course the subpanel will cost more; the benefit is versatility and fallback (e.g. if the big charger goes on the blink you can just use the little charger; you don't need to rewire the works.) – Harper - Reinstate Monica Dec 25 '17 at 5:21

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