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Home charging setup, challenging conventional wisdom.

Discussion in 'Model 3: Battery & Charging' started by SSedan, Aug 25, 2018.

  1. SSedan

    SSedan Member

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    I have a Model S but figured I would post here due to traffic.

    I see a lot of folks stress over the cost of big wire. Seems everyone recommends doing bare minimum wire size on a 14-50 install, well many people get free wall connectors later and a minor amount of extra cash now can let you better use that later

    Looking at a conduit setup.

    40ft run for a 100amp circuit is 80f of 3gauge at $1.02/ft. from Home Depot and 40ft. of 8gauge for ground at $0.56/ft so $104 worth of wire.

    40ft. 50amp 14-50 circuit is 3 conductors so 120ft of 8 gauge at $0.56 and a 50ft spool of 10gauge ground is $18.50 is $87.50

    Now the breaker upgrade from 50amp to 100amp is a $30 upgrade as well and conduit would need to be upsized too, but again let us remember people worry about the wire cost and I just demonstrated it isn't that big a difference, the conduit upgrade isn't going to be much.

    Rather than follow what everyone here tells you and just do a 8 gauge 14-50 install I think more should be considering upsizing the wire now in case you want to go to a wall connector later. One complication is the 14-50 is a 4 wires total rather than 3 but for $35 you can buy adapters, a 16-50 adapter would let you run a 3 wire outlet

    I would at least ask the electrician to run the conduit a little big so you have some headroom later.

    Just spitballing now what about running a 14-50 with as big a wire as fits the hot terminals(4gauge?) and then 8gauge as the neutral and 10 as ground and then if you go to a to a HPWC you can discard the ground and repurpose the 8gauge neutral as the new ground???

    I think most folks could spend an extra $100 or less on installs materials and labor for the hassle of bigger wire and have a real chance of saving themselves many times that later when they get a referral wall connector or just want a wall connector later. and on a Model 3 even a wall connector on a 60amp circuit is capable of 48amps, which you might not ever need but if the day arrives you will be happy you have it

    Yes 14-50 at 32amps with the UMC does the job but even on that same wire a HPWC will give you 40amps.

    I am not saying everyone needs a HPWC I am saying an extra $20 worth of larger gauge wire now might just let you use one to much greater effect later, or let you install two, more easily later if you get a second EV.

    Little overkill now is almost always cheaper later.

    If an electrician tried to talk me out of upsizing wire a bit with the idea of a future wall connector in mind later I would find another electrician because he just told you "bare minimum" is his mindset.
     
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  2. wycolo

    wycolo Active Member

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    > upsizing wire a bit [SSedan]

    Or even 2 bits - this is the gift that keeps on giving. Considering all the hours that are spent charging an EV, reducing the temperature of conductors means more KWHs are delivered instead to the battery.
    --
     
  3. BestHand

    BestHand Member

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    NEMA 14-50 outlet requires 6 gauge, not 8.
     
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  4. SSedan

    SSedan Member

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    If using Romex yes but I stated conduit setup implying THHN.
     
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  5. Runt8

    Runt8 Active Member

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    I always think it makes sense to build in overhead for the future assuming your panel can support it.
     
  6. SSedan

    SSedan Member

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    $20 extra on larger gauge wire even if you don't think the panel can handle it might still be worthwhile.
    Maybe you have an electric water heater or rangerang and go to gas, or if in a warm climate heat pump water heater without having to revert to the heating elements reducing total load.
    Less than a year before I bought my car we switched to heat pumps from baseboard electric in a 40yo 2400sq.ft. house near Green Bay. I had no capacity for an EV till I made that change.
     
  7. judyjetson

    judyjetson Member

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    Am i missing something here? Maybe it is because you have a Model S that you need a 100amp breaker? Keep in mind, this is the Model 3 forum, i believe you only need a minimum of a 60amp breaker for a Model 3 to achieve maximum charging rate with the gen 2 wall charger tesla.PNG
     
  8. SSedan

    SSedan Member

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    And as said who knows what your next car will support or ifa larger circuit might be used to load share for multiple cars.
     
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  9. Glamisduner

    Glamisduner Active Member

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    I was going to have an electrician install 4awg so I could upgrade to a HPWC later and charge at 48 amps.

    but electrician is suggesting that instead I run 2, 6awg runs, so I could add an entire second outlet for a second car later.

    Thing is, I'm thinking I would want the second outlet to be on the other side of the garage anyways (probably outside too).

    Thoughts?
     
  10. GWord

    GWord Member

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    4awg would be an unusual size for 48A. 75degC rated 6awg would get you there with the same type of installation. Your electrician may not know that HPWCs can share the same branch, although you should consider how complicated retrofitting a wire run for the second HPWC might be.
     
  11. BestHand

    BestHand Member

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    This table does not look right. If you will charge Model 3, S, and X with the same current model 3 supposed to have highest MPH, as it has highest mileage per KWH. For example 32A will charge M3 around 30MPH, while model S about 23 or a bit faster. This table shows only 44MPH for current 80A, but it should be about 30/32 * 80 =75 MPH.
     
  12. eprosenx

    eprosenx Active Member

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    The model 3 long range onboard charger maxes out at 48 amps so feeding it with any circuit larger than 60a won’t increase your charge speed where as in an S or X the speed continues to go up through 72 amps (90a circuit). 100a does not make it better than 90a unless you have an old model S with dual 40a chargers.
     
  13. Glamisduner

    Glamisduner Active Member

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    Forgot to mention it's about a 100 foot run. I would then need 4awg correct? 6awg is only rated for 55 amps @60c? Which means it's not quite enough to power 48 amp continuous?
     
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  14. judyjetson

    judyjetson Member

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    Table is directly from Tesla's website.
     
  15. BestHand

    BestHand Member

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    can you share a link please?
     
  16. judyjetson

    judyjetson Member

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  17. BestHand

    BestHand Member

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    Thanks for link. I noticed that table shows the same speed for current Wall connector maximum output 48A and higher. I think it just means that for settings 48A and higher model 3 charge rate will not be higher than 48A, which is about 44MPH.
     
  18. eprosenx

    eprosenx Active Member

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    Correct. If you are limited to the 60c column (due to the cable being NM style cable for instance), then #4 AWG is the minimum ampacity wire to support a 60a circuit. But if you do have to go up to #4 awg then you can actually instead install a 70 amp circuit if you want since it supports it even at the 60c rating.

    #6 in conduit will allow a 60a circuit.
     
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  19. eprosenx

    eprosenx Active Member

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    It all depends on your goal and what kind of car you thought the second one would be. (and also what capacity your main electrical service has)

    The ultimate way to install two Tesla chargers is with a single 100a circuit shared between them along with the data cable between them so they can coordinate. That way you can support up to 80a charging for a single car, or it can be spilt to 40a for each car if they both need to charge.

    Doing two 50a (40a continuous) circuits is the same load calculation impact but your max charging rate is 40 amps per car even if the other one is idle.

    There are a million options here.

    Oh, and if the run from your main panel to the garage is a long way, one popular thing is to run say aluminum wire from the main panel to a subpanel in the garage, and then run wire from there to whatever charging setups you put in the garage. This way changing it around later in the garage is a lot easier...
     
  20. GWord

    GWord Member

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    6awg Romex is rated for only 55A and would not support 48A continuous charging, despite having a 60A breaker. That's why I was stating 75deg rated, 6awg conductors, although you will have to have them in conduit. The 100ft length will produce a voltage drop of around 5V at 48A which is within the 3% recommendation that the NEC makes.
     

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