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How to wire the garage...question for the electrical engineers in the crowd...

Discussion in 'Model S: Battery & Charging' started by wshepherd, Dec 10, 2011.

  1. wshepherd

    wshepherd Member

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    We're remodeling our house, and in the process are going to build a new garage. Any recommendations on what to install power-wise with an eye towards future proofing? Was thinking two circuits of 240V/50A (2 car garage) to power the model S on order and maybe someday a model X in the next bay.

    My general understanding is that 480V is not really doable at home (and isn't good for the battery anyways on a routine basis). Any point in doing more than 50A? Do the economics change meaningfully to do more? Putting in a new 400A service for the house, so not too concerned about total draw. Any safety issues we should worry about/ask our contractor to address at that kind of power draw? (Know some of the Volt issues have reportedly been home wiring issues).

    Thanks,
    Bill

    sig #501
     
  2. Mycroft

    Mycroft Life happens

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    You only need more than 50A if you're planning on installing an HPC which would be hard wired. Other than being cool and convenient, the HPC is a bit overkill.
     
  3. Doug_G

    Doug_G Lead Moderator

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    +1. You don't need an HPC for overnight charging.

    I have an HPC in my garage. I think it's been used at 70A more often for the Toronto demo Roadster than for mine! I usually charge at 40A; otherwise my garage gets rather hot.

    With 90A wiring, the HPC was significantly more trouble and expense to install than simply wiring in a 50A circuit. I ended buying a UMC for KOA charging anyway, so the HPC really wasn't money well spent.

    An HPC would be very useful for highway charging. I'd sure love to see one along the 401...
     
  4. wshepherd

    wshepherd Member

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    Thanks. Any thoughts on safety issues with a 50A circuit, or is it straightforward for a good electrician? any safety features to build in?
     
  5. jory

    jory Member

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    install a large diameter conduit back to the distribution/breaker box. you can decide later what to run through it. minimum size for the recommended HPC 4-gauge wires is 1" conduit. i would go with larger than that (2" maybe? more even?) to allow for flexibility. make sure you have extra space in your box for additional/new breakers.
     
  6. Doug_G

    Doug_G Lead Moderator

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    Straightforward. The connector won't apply power to the car until everything is safe. You might want to put in some kind of hook for holding the cable when not in use.
     
  7. VolkerP

    VolkerP EU Model S P-37

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    make sure the electrician understands this wiring is to deliver 40amps for hours. No getting away with badly crimped spots getting hot after a few minutes, but settle down after you're finished boiling tea water.
     
  8. Mycroft

    Mycroft Life happens

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    Any electrician can install a 50A circuit. It's the same as most kitchen range outlets. 3 x 6-gauge wires, ground the box, and you're done. You only need conduit if it's exposed.
     
  9. richkae

    richkae VIN587

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    Run Cat6 or Cat5e network cable or give yourself the ability to pull it afterwards. You should be adding it to any remodeled parts of the house anyway.
     
  10. de704

    de704 XP268

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    #10 de704, Dec 11, 2011
    Last edited: Dec 11, 2011
    Why would you risk doing this yourself when there's a tax credit to have it installed by a professional. I wouldn't skimp on the charger after I just paid $57k+ out of pocket for a car.

    You might end up like the volt owners and have a burnt car because of faulty charger wiring.
     
  11. Mycroft

    Mycroft Life happens

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    1. Who said anything about doing it themselves?
    2. The tax credit is only for chargers installed this year, so not applicable.
    3. The "faulty wiring" was plugging the Volt into a three-way adapter plugged into an overloaded 110v outlet.

    All that said, I'll be doing mine myself because I know what I'm doing and I'd rather save the money for more important things like paying off the car.
     
  12. doug

    doug Administrator / Head Moderator

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  13. Thumper

    Thumper Member

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    Mycroft, When I read the IRS form 8911 for this year, it looks like a tax credit for any charging infrastructure will qualify. How have you determined it does not? I'm not really challenging you, I am getting my 50amp circuit on Monday and had hoped to get a partial credit by beating the end of the year. http://www.irs.gov/pub/irs-prior/f8911--2011.pdf
     
  14. Mycroft

    Mycroft Life happens

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    Feel free to claim it Thumper.

    My view, (and I haven't checked with an accountant or the IRS - even if I had, the IRS is known to give out conflicting information), anyway, my view is that since I don't currently have an EV, I can't claim to have placed the 50v outlet "in service".

    Now, if you install the outlet on the exterior of the garage and have proper signage that the outlet is available to any EV for charging, then you might honestly claim that it's "in service".
     
  15. Robert.Boston

    Robert.Boston Model S VIN P01536

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    Or invite a Roadster owner over; in my uninformed opinion, once it has charged any EV, it is in service.
     
  16. Thumper

    Thumper Member

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    I see your point. I'm a much more favorable interpreter of the text than you. If the outlet is hot and could be used it is in service as far as I'm concerned and that's the way I expect to defend it to the IRS. I'll sign up on PlugShare. Then it is truly in service and advertised on the internet.What do you think?
     
  17. Mycroft

    Mycroft Life happens

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    Sounds like a good plan to me. The odds of getting audited are fairly slim anyway and I've been told that it's best to claim every deduction no matter how tenuous. If by chance you're audited and they toss a few of them, then you just pay the taxes you would have owed anyway plus a small penalty. It's not like we're trying to claim a million dollar tax exempt trust or something.
     
  18. Dan5

    Dan5 Member

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    Just did the wiring recently- it's really easy
    Get size #6 wire
    50 A, 220 V breaker

    Step 1: turn off the main breaker
    Step 2: Install the breaker ( make sure you get one that fits)
    Step 3: Install the wire fish it through the wall
    Step 4: Install the circuit
    Step 5: Install the outlet (pending the Tesla's info for plug)

    It's relatively easy, but then again, I'm an engineer, but it shouldn't take more than 1 hr to do for a normal person to do. Honestly, epoxying the floor was more time consuming the putting the circuit
     

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