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Thread: Home electric car charger prewire requirements

  1. #1
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    Home electric car charger prewire requirements

    2 or 3 wires on prewire requirements for 240v car charger?
    Got a Ph.D in DIY...

  2. #2
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    The Tesla charger that I installed had a capacity of 100A at 240V. No neutral. I don't know about other brands.

  3. #3
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    Quote Originally Posted by buzzbar View Post
    The Tesla charger that I installed had a capacity of 100A at 240V. No neutral. I don't know about other brands.
    Since this is a prewire, with no idea what the eventual car or charger will be, you really need to pull a neutral. You could probably get by with a reduced size neutral in practice, but there is no way to justify that without a specification.
    Some 240V chargers will use 30A or less while others like the Tesla can use up to 100A.
    A conservative prewire for most applications would be 240V/50A. Some chargers may require you to fit a smaller breaker at install time if you so this.

    It is most likely, especially if you have 120/240 3-wire, that the charger would only need the neutral for control and indicator power.

  4. #4
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    Good point.
    I was thinking of doing the minimum with a 20A circuit , 3 wires.
    Got a Ph.D in DIY...

  5. #5
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    Have installed dozens of Level II EV chargers: Seimens, Leviton, Legrand are all straight 240 with no neutral (2 lines and a ground).

    For pre-wiring I'd pull the Neutral; Better to have it and not need it than vice-versa.

  6. #6
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    Quote Originally Posted by constantsolar View Post
    Have installed dozens of Level II EV chargers: Seimens, Leviton, Legrand are all straight 240 with no neutral (2 lines and a ground).

    For pre-wiring I'd pull the Neutral; Better to have it and not need it than vice-versa.
    Yes, I believe that straight 240 volts with no neutral is the norm, party in order that the same charger may be used almost worldwide, in counties such as the UK with single phase 240 volts, and in places like the USA.

  7. #7
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    Quote Originally Posted by constantsolar View Post
    Have installed dozens of Level II EV chargers: Seimens, Leviton, Legrand are all straight 240 with no neutral (2 lines and a ground).

    For pre-wiring I'd pull the Neutral; Better to have it and not need it than vice-versa.
    Is there a standard circuit size (ampacity) you install? I'm thinking that if someone asked me to put in a circuit without yet knowing the particular vehicle, what size would make sense.

  8. #8
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    Sep 2004
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    I think an 8-3 circuit on a 40A breaker will cover a lot of possibilities (perhaps even 8-2 would be fine if you just recolor the white if it ends up being a 240V charger). But the higher end things (e.g. Tesla's) may need more. Future vehicles may also change.

    I put a box labeled "car charger" with a raceway in my last garage so you could pull what was needed. But it was a 3/4" conduit, so you're still not going to get above 60 amps.
    Mark
    Kent, WA

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