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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.
    • Informative x 1
  7. Sandy240

    Sandy240 Member

    Jul 15, 2013
    The answer to this question is YES, and Tesla explicitly supported installation with the HPWC with 277 line-to-neutral on a 4-wire 3-phase 480 supply. But Tesla removed this installation option from their most recent HPWC manual because it turned out that 277 Volts was a bit too close to the internal max on the on-board charger, which I was told by the tech at the Tesla charger support line (not verified or documented elsewhere), is something like 282 V, and actual line voltages can vary and too often exceed the internal fault level.

    To see the earlier version of the HPWC manual, search for Tesla part number PN: 1069742-00-A The "277V Three-Phase Wye-Connected" installation option is on page 9.

    This link to the manual may still be valid:

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