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Home Wall Connector Installation - Circuit Breaker Size?

Discussion in 'Model X: Battery & Charging' started by ThomascCTT, May 5, 2017.

  1. ThomascCTT

    ThomascCTT Member

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    I will be installing the Home wall connector soon in anticipation of my Model X WITHOUT the High Amperage Charging Upgrade. I know I'm only required to have a 60Amp Circuit Breaker but my question is other than possibly increased installation cost, Is there any reason I shouldn't opt for a 90Amp Circuit Breaker to future proof my installation in case I upgrade later?

    Maybe a dumb question I'm just not sure if the increased power will have an adverse effect when charging the car or if it will regulate it's self to what the car can handle. I'm fairly confident it won't be an issue but I'd rather ask then find out after I installed.


    THANKS.
     
  2. john pane

    john pane Member

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    It's more than a matter of selecting a circuit breaker. Higher amperage will require heavier wire, and greater than 60A will require a disconnect within sight of the charger. Notwithstanding these differences and the associated costs, it is worth considering.
     
  3. Solarman004

    Solarman004 Member

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    Protecting the HPWC is the secondary function of the breaker. The primary function is preventing over-current and fire in the wire. You certainly can go with a 90 amp breaker (assuming compatibility with your breaker box and total house service), but per code, you need the appropriate gauge wire, for the run length, to the HPWC.
    For THWN copper wire, you need AWG 3 wire or larger in a 90 amp circuit. This can change for long runs. It's best to hire an electrician to make sure you are code compliant.
    You can find wire size requirements here.
     
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  4. Zero CO2

    Zero CO2 a long term goal

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    You are not required to have a 60 A breaker.... the HPWC can be set to many different breaker sizes 15A-100A there is a rotary switch that you set to the desired output current and breaker size ... so you need to figure out what your electrical feed/panel and household load can handle
     
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  5. animorph

    animorph Member

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    We installed a 100A circuit and breaker. We expect to have the current Model X and a Model 3 in the future. One HPWC now and we'll install another before the 3 gets here. They can share the 100A circuit as needed. The X has the 72A charger, so it can charge a bit faster with the 100A circuit all by itself.

    You could also share a 60A or 90A circuit, so all you get is a bit more charge speed, if you can use it, for your extra amps.
     
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  6. ThomascCTT

    ThomascCTT Member

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    Thanks for the responses. It sounds like I shouldn't have a problem installing the 90 or 100A circuit (assuming the house can handle it).
     
  7. sdorn

    sdorn Director of Awesome

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    Yes, it really depends on your house. If you have plenty of capacity and a breaker box in your garage, that is going to be the cheapest install. In my situation the breaker boxes were in the basement, and I was already over capacity on my 200 amp service, so I ended up spending just under $10,000 to have the service to my house upgraded to 400 amps and a 100 amp circuit run to my garage from the basement including the required local disconnect and installation of the Tesla HPWC.
     
  8. Zero CO2

    Zero CO2 a long term goal

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    One other point on this topic.... i see in many of the posts on this site EV owners wanting to maximize the output current , it seems to me that you also needs to think about your typical driving pattern and how many EVs you think you will own over time before investing in upgrading your entire house electrical system(which can get quite expensive) ... in some cases there will be no choice but to upgrade....however....
    as an example if you commute/drive 70 ,miles per day it takes ~ 2 hours of charge time with a 48 amp output current... how often will you need to charge in 1 hour vs 2 hours overnight?.... I would speculate that for most people 1 hr vs 2 hrs of charge time while you are sleeping provides no real benefit for the potential increased cost in your homes electrical system.... just sayin...
     
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  9. TallPaulS

    TallPaulS Member

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    There are so many variables to consider as most have pointed out. Keep in mind the 80% rule for load vs breaker. A 60A breaker will allow charging at 48 amps, a 90 will give you the max for model X (72) and 100 is for an S with dual charging (80).

    Wiring for 90/100 amp service can get atrociously expensive, not to mention that even with 200 amp service you may breach capacity when considering A/C and other potential concurrent draws. Most jurisdictions tend to follow NEC for wiring requirements but each jurisdiction may also have their own requirements above and beyond.

    Even if you have dual units for your home (the new generation) they can share a 60A just fine, and unless you're doing >200 miles on both electric vehicles every day an overnight charge can easily fill both.
     
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  10. Teacherspet

    Teacherspet Member

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    Do you use two 50amp breakers and number 6 wire
     
  11. Teacherspet

    Teacherspet Member

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  12. Solarman004

    Solarman004 Member

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    This will work if the HPWC is set internally for 40 amps maximum output.
    You can refer to this chart: http://www.cerrowire.com/ampacity
    and see that 6 AWG copper THHN or THWN is an appropriate size for a 50 amp circuit.
    Note that you will not use 2 separate breakers, but rather a double 50 breaker where both poles are connected and turned on or off at the same time.
     
  13. Krazaak

    Krazaak Member

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    If you're wiring for 80A of charging, it requires a 100A double-pole breaker and #3 THWN wire in conduit. The only cars that use 80A though are older Model S with dual chargers.

    The most you need for refresh Model S or X with high amperage chargers is 90A on the breaker for 72A continuous, but that still requires #3 wire, so nothing really saved.

    If you have the regular charger on the S or X, it tops out at 48A and you need a 60A breaker and #6 THWN wire. That's more than enough for most people.
     
  14. Rocky_H

    Rocky_H Active Member

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    It's called a 2-pole circuit breaker, not two breakers.
     
  15. BluePhoton

    BluePhoton Member

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    Here's my planned scenario:
    Two HPWCs for one Model X (72A max) and one Model 3 (lower max)

    My question:
    Is a shared 90 amp circuit sufficient or should I go with 100 amps?

    Reasoning:
    While the 90 amp is fine for just the Model X = 80% of 90amps = 72amps = Model X max.
    Having another vehicle connected and idle reportedly takes 8 amps of current.
    So, with a 90 amp circuit, it would seem I'm reducing my Model X charging by 8amps if the Model 3 is also connected and idle...

    Moving up to a 100 amp circuit (providing 80 amps total available = 72 full to Model X, 8 amp idle to Model 3), would solve that issue, no?

    Thanks!
     
  16. animorph

    animorph Member

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    The real question is will the 90A circuit charge your cars as fast as you require. I can't imagine you'll be missing a dinner reservation because both of your cars are at 0% and 72A can't charge one of them fast enough. For normal overnight charging I don't think you would notice the difference.

    I do use a 100A circuit and will have a Model 3 hopefully sometime this year and have an X now.

    #1 - You are constrained by the number of amps a load calculation shows are available through your electrical panel. I was barely able to squeeze out 100A from our 200A panel. You can estimate this online or your electrician can do it as part of an estimate.

    #2 - As far as cost, I don't think a 90A circuit would save a significant amount over a 100A circuit. Not sure the wire size would even be reduced. Why is 90A looking like your baseline currently?
     
  17. BluePhoton

    BluePhoton Member

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    Good point about "need". I don't think it's a big deal - just trying to do it right...

    #1 Capacity: We went solar two years ago - at that time I had our panel upgraded from 200 amps to 375 amps (specifically to add capacity for electric car charging). So, I think we have the room for dedicated 100 amp circuit.

    #2 - Cost - I think the electrician just defaulted to 90 amp in his estimate, as that is maximum needed for most scenarios - the dual HPWC scenario is still pretty rare, I guess... I've reached out the electrician about changing to 100 amp circuit - I will share any price difference.
     
  18. GatorGuy

    GatorGuy Member

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    If you are going to being sharing the circuit then there is no reason to not go as large as you can. 100 isn't going to gain you much over 90 but you do gain something. You don't gain anything by going less. Both requires the same gauge wire.
     
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  19. Rocky_H

    Rocky_H Active Member

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    You are really overthinking this and worrying too much. Remember that the two wall connectors dynamically reallocate power constantly. You seem to be thinking about this in the paradigm of needing full power to both and if one is limited, it will always be limited. But when one gets full and stops requesting power, the wall connectors will shift those extra amps over to the other car. So if one is limited for 2 or 3 hours, that's not that big a deal, because you sleep longer than that.

    Here's a good way to think about the big picture of this. Think of how much total power you have to figure how many total rated miles that can supply to all of your cars. Whether it goes to one car first or the other or whether they go slower or faster doesn't really matter versus just having it all done by morning.

    So your 240V 90A circuit can supply 72A constant current. I'm going to use a ballpark number for rated miles based on my Model S. You have a Model X, which would get less and a Model 3 that would get more, so using the S number is reasonable for an average. That is about 52 miles added per hour for that 72A feed. 52 miles times 8 hours of sleeping is 416 total miles you can add across both cars each night. I'm fairly certain that you don't drive over 400 miles every day, so yes, the 90A circuit is more than enough to cover both vehicles.

    (Edit: And...there's the predictable Tim Taylor contingent recommending to always go bigger, no matter what.)
     
  20. BluePhoton

    BluePhoton Member

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    I'm not really looking for max power to both cars at the same time - If I wanted that, I would do two separate circuits.

    When talking about a 90amp vs 100amp circuit for two chargers, I'm talking about the fact that the "max" for one car will be limited to 64 amps (72 amps - 8amps) if the other car is attached yet idle (given that idle car still grabs 8 amps, I've read). Going up to 100 amp circuit (i.e. 80% = 80 amps available) would solve this, as the max 72 amps would still be available for the car that needs it.

    Thanks!
     

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