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Advice needed on electrical preparations for Model S

Discussion in 'Model S: Battery & Charging' started by BigAirHarper, May 6, 2016.

  1. BigAirHarper

    BigAirHarper Member

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    So my wife and I will soon take the plunge for a Model S and I'm wanting to get the garage prepared. My goal is to have a HPWC and a NEMA 15-50 outlet, in case something goes wrong with HPWC. My main panel is in my garage but there are only 3 slots available. I have a sub panel on backside of garage, outdoors, with 2 slots open. So my question is, what's the best way to configure my wiring setup given what I have in the panel and what I want for charging? Pics of panel below....
     

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  2. davewill

    davewill Member

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    #2 davewill, May 6, 2016
    Last edited: May 6, 2016
    My first reaction is that there must be another panel around somewhere. I expected to see a double breaker in the big panel feeding the smaller panel as a sub, but I don't see it. To me that means that there's either another panel around, or some other kind of tap into the meter to feed the second panel. Without knowing the size of the service or the size of the feeder to the subpanel (or even which, if either or both, is a subpanel) it's hard to know if you have capacity for the circuit. If that big panel is the main (probably is), and the service is big enough, I'd add the circuits there since it's actually IN the garage. The number of open slots isn't a worry because I'm pretty sure those panels can take half-height breakers.
     
  3. BigAirHarper

    BigAirHarper Member

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    There's the main meter panel where power comes into the house. The big breaker pictured is in garage and is my main panel. Maybe sub panel is wrong word for outdoor one. I also have 2 more panels outside for pool equipment but their location is obviously not as good.
    What's an easy way to check the amount of service going to the panel?
    Any links to half height breakers? This is what I was thinking of using for HPWC:

    Square D Homeline 100 Amp 2-Pole Circuit Breaker-HOM2100CP - The Home Depot
     
  4. davewill

    davewill Member

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    Look in that "main meter panel" you described. There should be breakers there feeding these two panels (and any other panels you have) which would make both of these subpanels. If you're lucky you should also see the main breakers for the whole house that will tell you the size of your service.
     
  5. BigAirHarper

    BigAirHarper Member

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    Ok saw exactly what you described. Main panel has 5 slots, 4 in use. The main sub in garage had a 100 amp 2 pole breaker on it....
     
  6. davewill

    davewill Member

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    Well, you now need more help than I can provide. The only thing I'm sure about is that you don't have enough capacity in that garage subpanel for a 100a circuit, much less a 100a plus a 50a, irrespective of the number of slots or the use of half-height breakers. I think you're looking at either putting in a smaller charging circuit, or running a new feed from the main panel. How far away is that main panel?
     
  7. BigAirHarper

    BigAirHarper Member

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    Main panel is 20 feet away on the outside wall of garage. I'm wondering could I swap the 100A breaker on main panel to 150A, then the garage sub could handle the additional circuits. The only big power draw on the garage panel is the oven. All other major appliances have their own location on another sub panel.
     
  8. Edmond

    Edmond Permanon

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    NOO, that breaker is likely sized to the wiring going to it and the anticipated load.

    I would get the utility out there to check that the drop can handle the new load, and then run a line from that outside main panel.
     
  9. davewill

    davewill Member

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    Most unlikely. The breaker is sized to protect either the wire going to the subpanel, the subpanel itself, or both. You would almost certainly have to upgrade the wire and possibly the panel to change the breaker. Better to run a new line to new subpanel, where you can put your two circuits. and as Edmond pointed out, you have to be sure your service is big enough to handle it.
     
  10. BigAirHarper

    BigAirHarper Member

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    Yea before I do any of this I'm consulting an electrician, just wanted to get an idea of my options. And of course checking the gauge wire in the wall before any breakers are switched is a must. The main sub panel is a 200amp panel so that side of things is good.
     
  11. tnt1971

    tnt1971 Member

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    Congrats on your order. I don't know if it is the same in FL, but in NY there is some crazy formula with what is in the panel and what you can add. I have 200 amp service as well and we have all gas applicances (stove, heat, and dryer). All we have that is a big draw is central AC. The rest is lights and outlets. My electrician told me to do 80 amp for the dual chargers I would have to upgrade the panel to at least 250 amp. I had enough for 40 amp. If you have electric appliances you may need an upgrade.
     
  12. AndreSF

    AndreSF Member

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    It might not be a traditional approach, but if you are looking for NEMA outlet as a backup only, why not have electrician bring NEMA 14-50 outlet to the charging point, wire HPWC to that outlet (vs hardwired).

    Good luck!
     
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  13. BigAirHarper

    BigAirHarper Member

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    I thought about this, however I wouldn't have the full charge rate of the HPWC, granted I'll probably never need it, but in the off chance I do, I would love to just have the 80A available just in case.
     
  14. AndreSF

    AndreSF Member

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    Speaking from a practical point on owning EV (4th year EV owner), you will unlikely need 80A for overnight charging. However, if you looking to upgrade you service and garage panel(s), obviously that is an option too...
    FYI I charge nightly at 15A (using EVSE that was installed when I drove Volt). Car is fully charged every morning. If EVSE goes south, I will trickle charge from 110V, but ultimately can drive a few days w/charge. Closest super charger is about 25mi.
     
  15. FlasherZ

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

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    See my FAQ from my signature, below.

    I can pretty much guarantee you don't have the appropriate wire to swap a 100A breaker to a 150A breaker. It will likely need a larger conduit as well.
     
  16. BigAirHarper

    BigAirHarper Member

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    Yea meeting with electrician Monday. Decision has changed to just run an entire new sub panel, have HPWC and 15-50 NEMA on panel, then run additional 15-50 NEMA from current sub panel so we are prepared for the 3.
     

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