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HPWC can I use it on a 50 amp breaker?

Discussion in 'Model S: Battery & Charging' started by Larry, Sep 17, 2013.

  1. Larry

    Larry Member

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    Since the twin chargers are bundled with the HPWC Im stuck with it. I cannot install a 100 amp breaker without major expense. Can I still install the HPWC on a 50 amp breaker realizing I will only charge at 40 amps? Since Im stuck with it thought I would try to use it. I dont need the fast charging of the HPWC so a 14-50 is fine but what do I do with the HPWC if I cant install it?

    Thanks again
    Larry
     
  2. Zapped

    Zapped Model S - PURE EV

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    In a previous thread someone had suggested to sell it.
    Maybe offer it here or eBay
     
  3. efusco

    efusco Moderator - Model S & X forums

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  4. evmile

    evmile Member

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    Yes. There are DIP switches which can be set to whatever current you have available.

    Screen shot 2013-09-17 at 9.27.20 PM.png
     
  5. Larry

    Larry Member

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    Anyone know what size of wire would be needed for installing the HPWC on a 50 amp circuit so I can inform my electrician?
     
  6. mitch672

    mitch672 Active Member

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    It depends on the wiring method, but in general for THHN in pipe, #6 copper for the 2 hots, #10 would be the minimum for the ground. Your electrician will be able to advise you on the correct gauge, based on the wiring method he uses, I wouldn't worry about it.
     
  7. evmile

    evmile Member

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    I think 6 AWG.
     
  8. markb1

    markb1 Active Member

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    Someone also was told they could simply return it to Tesla for a refund.
     
  9. Larry

    Larry Member

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    Thank you!
     
  10. LASpark

    LASpark Member

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  11. aviators99

    aviators99 Model S - R140

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    If you can, I would use the wire required for a 100A breaker in case some time down the road you decide you want to spend the money to upgrade your service. Otherwise you will also have to spend a bunch extra to replace the copper and discard what you used.
     
  12. Larry

    Larry Member

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    Thanks aviator, this is exactly what we are going to do
     
  13. FlasherZ

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

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    As mentioned, your electrician should know. For copper, 50A would need minimum #8 if THHN in conduit, #6 if NM-B ("Romex"). Minimum ground size is #10 copper for up to 60A circuit breakers. Reason the #6 is needed if you're using NM-B/Romex is that by code you must use the 60 deg C temperature for it (despite the fact the conductors in the cable are THHN or THHN-2 anyway), and that limit is 45 amps for #8.

    If you're doing wire for 100A in the future, you'll need to run a minimum of #3 copper with a #8 copper ground. Some electricians will just upsize it to #2.
     
  14. Larry

    Larry Member

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    Having it done. Hes running #3 in 1 inch metal conduit and Ill probably set the dips for'80 amps to be a little easier on the system. Thanks again for your help
     
  15. vgrinshpun

    vgrinshpun Active Member

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    #15 vgrinshpun, Sep 20, 2013
    Last edited: Sep 20, 2013
    Just to clarify, National Electrical Code (NEC) requires that cable be sized based on temperature rating of the terminations, NOT just based on maximum temperature rating of the cable insulation. Since temperature rating terminations for the circuits less than 100A is 60Deg C, the cable for 50A circuit must be #6.

    - - - Updated - - -

    You've got good electrician, Larry. Running anything less than #3 for the circuit protected by 100A breaker at the panel would be violation of National Electrical Code (NEC). The key here is not the load that this circuit will see (you mentioned that you do not plan to use more than 40A), but the fact than NEC requires that cable be protected by the associated breaker, i.e. allowable ampacity must be equal or higher than the rating of the breaker. For the #3 the 75Deg. C ampacity is 100A, so this circuit requires #3 as a minimum.
     
  16. FlasherZ

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

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    #16 FlasherZ, Sep 20, 2013
    Last edited: Sep 20, 2013
    Yes, the terminations come into play in the big picture, however, you're incorrect that 50A circuits require #6.

    You are correct in that the code tells you that by default, the 60 deg C rating is to be used. However, your blanket statement that the temperature rating is always 60 deg C for less than 100A is incorrect - 110.14(C)(1)(a)(3) notes the following may be used: "conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors"... every breaker and receptacle I have on my workbench today is listed for 75 deg C, and I have a sampling of types and brands. The ampacity of #8 wire at 75 deg C is 50A.

    There are two cases, though, when you must use the 60 deg C column, and they're specified by articles 334 and 338, where NM and SE cable are used for branch circuits - the 60 deg C column must be used for those cable types.

    As a result, you only need #6 when you're using NM and SE cable assemblies, but THHN/THWN wire in conduit is fine at #8 for 50A.
     
  17. vgrinshpun

    vgrinshpun Active Member

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    I agree with everything in your post, FlasherZ, except the comment on big picture. The default is there for a reason. Unless you or I have information on what specific breaker is installed in Larry's panel, and what is temperature rating of the terminations, the proper thing to do is to suggest using default. Your advice to Larry was correct for a specific cable used, but bear in mind that these posts will be read and used by others (I've done it many times with posts which contain information outside of my area of expertise), so using default is the only right answer here. That is the reason i wanted to add the clarification.
     
  18. FlasherZ

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

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    #18 FlasherZ, Sep 20, 2013
    Last edited: Sep 20, 2013
    Well, ohhhhhkay then. Thanks for the opinion. For what it's worth, I haven't seen a 60 degree breaker in a very, very long time. Very few of us will go by 60 deg C by default, because 1) everything is labeled today, and 2) very few low-temp terminations are found anymore except in ancient panels. Telling someone they require #6 when they really don't need it (for wire-in-conduit applications) is wasteful, and if you're a tradesman, you'll lose jobs that way - especially when you misquote or misunderstand the code. You may find Uncle Jesse in Arkansas with a 1940's 4-branch fuse box that's not rated for temp, but that's the very, very rare exception.

    To the OP, the FAQ:
    FAQ: Home Tesla charging infrastructure QA
    ...gives you the appropriate information you need.
     
  19. aviators99

    aviators99 Model S - R140

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    Hang on: Are you saying you will set the dips for 80A with a 50A breaker?
     
  20. FlasherZ

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

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    I made an assumption that it would be set for 80A once a breaker were put in place for 100A down the road. I would hope it's obvious that 80A HPWC on a 50A breaker = 0 current after about 30 seconds or so. Just to be sure, I'll make it clear that would trip most circuit breakers. Under no circumstances should you do that if you have Federal-Pacific Electric StabLok panels or Zinsco panels.
     

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