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Charging 277/480

Discussion in 'Model S' started by Brightonuk, Sep 11, 2015.

  1. Brightonuk

    Brightonuk Member

    Mar 16, 2014
    I am looking to install a 220 type nema 14-50R 250v outlet at my office my electrician tells me I have a 277/480 panel can I wire up to this panel?
    He said I need to check that the car will be OK charging with this output
  2. 365gtb4

    365gtb4 Member

    Jun 5, 2015
    You will need a step-down transformer to drop the voltage. The cost will depend on the the current to be supplied by the transformer. Check and see if your location already has a step down transformer, most locations do.
  3. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Jun 21, 2012
    Your electrician has issues if he was willing to wire up a 14-50 from a 480Y277 panel, whether the car can take it or not. The answer as noted by 365gtb4 is no, and as noted you usually find a 208/120 Y or 240/120 delta transformer installed to provide support for lower-voltage loads.
  4. Cottonwood

    Cottonwood Roadster#433, Model S#S37

    Feb 27, 2009
    If you look at the HPWC manual, it allows for installation from neutral to 240 Volts (L-N). This does not work for a 14-50, however. A few companies sell "buck" transformers that will "buck" the 277 Volts to 240 Volts (L-N) and be within the spec of the HPWC. The advantage of a "buck" transformer is that it only needs the VA rating of the "bucked" power. In this case, 1-240/277 or 13.3% of the VA requirement of a full on isolating transformer.

    OTOH, if you have a 480/277 panel, you probably already have some 208/120 panels fed by existing 480/277 to 208/120 transformers. It's far easier, simpler, and cheaper to just connect a 14-50 or HPWC to 208 Volts and take the 13% hit in charging power.
  5. StaceyS

    StaceyS Member

    Jul 10, 2015
    Bend, OR United States
    Ask Tesla to install a Supercharger. Those run off 480v... :smile:
  6. Oba

    Oba Member

    Jun 7, 2015
    #6 Oba, Sep 11, 2015
    Last edited: Sep 11, 2015
    Well, here's a thought. The onboard charger in your car has no problem with 277v, so yes, you could use that power. You could also have the electrician install a NEMA 7-50R, and you've covered that part... 277v / 50a available from the wall. Under no circumstance would I recommend using the NEMA 14-50R on this higher voltage, as somebody could plug something into it that won't like it!!! It would absolutely SMOKE the electrics in a motor home which would normally use a NEMA 14-50.

    So, it's connecting the two that's a problem. To my knowledge, every EVSE on the market (including UMC / HPWC) is limited to 240v +/- 10%, which is 264v max.

    You could build a custom unit from an OPENevse with electronics to handle 277v. Or, test out a cheap EVSE to see if it goes up in smoke at 277v?

    To do this experiment with any "plug-in-the-wall" unit, you'll need an adapter from that plug (say, a NEMA 14-50R) to the NEMA 7-50P.

    Be cognizant that 277v and a neutral is not the same as two 120v lines that make up 240v. It is something that can be done, but the easy(er) answer is a somewhat expensive transformer, as suggested above.

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