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HPWC ground wire gauge

Discussion in 'Model 3: Battery & Charging' started by ACAG, Jan 7, 2020.

  1. ACAG

    ACAG Member

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    I am installing the HPWC with a 60 amp breaker and using THHN 6 gauge wire for my hot legs. What gauge should I use for the ground wire... I was going to use 10 gauge THHN wire?
     
  2. mongo

    mongo Well-Known Member

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    That appears to be correct per NEC:
    Equipment Grounding Conductor Table 250-95

    HPWC installation instructions do not call out full sized ground, like some other appliances (hot tubs) do.
     
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  3. Nogasmn

    Nogasmn Member

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    I used 4 awg wire for my install and the ground wire that was bundled was 8 awg. So 10 awg will be ok. How long of a run that you are using 6 awg for a 60 amp set up?
     
  4. ACAG

    ACAG Member

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    40 to 50 feet......what size breaker did you use for your install?
     
  5. Nogasmn

    Nogasmn Member

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    I used a 60amp breaker. After plugging in your run distance into a online wire size calculator, its says you need to use 4awg wire not 6awg. Have you already purchased the wire? I made the mistake of buying off amazon and since it was a cut to length purchase by the time I realized my mistake I couldn't return it. I could have saved another ~$100 if I had got the wire from Lowes.
     
  6. ACAG

    ACAG Member

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    I checked with an online calculator for wire size and run (please see pictures below)... With both a 100 ft run and 50 ft run, giving me results of using a 8 gauge wire and a 6 gauge wire, respectively. Screenshot_20200107-113952.png Screenshot_20200107-113919.png
     
  7. MrMassTransit

    MrMassTransit Supporting Member

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    My HPWC uses 10 gauge for the ground. The run from the panel (which at the service entrance, practically) is about 80-90 feet. However, my HPWC is on a 30 amp breaker because I have 100 amp service (condo building). The hot wires are 8 gauge.
     
  8. ACAG

    ACAG Member

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    Also, can both lines of a 240 volt circuit be the same color... i.e. Black?
     
  9. JamstationP85D

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    The Tesla wall connector I have doesnt require a Neutral so I just capped the 3rd 6 gauge cable. The ground wire in the Romex 6/3 looks to be about 8-10 gauge. The receptacle inside the Tesla wall charger could barely even handle that size.
     
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  10. mongo

    mongo Well-Known Member

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    Yes.
     
  11. Sophias_dad

    Sophias_dad Supporting Member

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    BTW, I wouldn't trust that calculator at all.... #8 in conduit is never allowed to carry 60 amps. Regardless of whether its in romex or conduit, and even if you ignore the 75c rating of the HPWC's connectors.

    Ampacity Charts - Cerrowire

    Note that the ratings on that page are without regard to distance... that is, you need to find an appropriate calculator to tell you if the losses are acceptable for a given length...

    https://www.southwire.com/calculator-vdrop
     
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  12. ACAG

    ACAG Member

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    How long was your wire run?
     
  13. Sophias_dad

    Sophias_dad Supporting Member

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    https://www.southwire.com/calculator-vdrop

    For 3% drop on 6AWG carrying 48 amps(its really carrying 48 amps, even though the THHN has to be rated for 60), you can go 169 feet overall(bidirectionally, pair of parallel conductors)

    Interestingly, that calculator says the 6AWG won't take 60 amps... they must be assuming Romex/60c ratings, which I'm pretty surprised they would leave as an assumption.
     
  14. doghousePVD

    doghousePVD My grandfather’s car

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    I think it can be, but suggested practice is one black, one red. White is definitely verboten.
     
  15. Sophias_dad

    Sophias_dad Supporting Member

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    #15 Sophias_dad, Jan 7, 2020
    Last edited: Jan 7, 2020
    White is allowed, but you need to put some colored(not white, grey, or green) electrical tape near each end of it, so the person to next screw with it knows it might be live.

    Its a little dated, but here's a reference.

    https://www.ecmweb.com/national-electrical-code/qa/article/20890543/stumped-by-the-code

    Note: upon rereading this, it's really intended for a cable like romex where the conductors are already built in and not changeable, not THHN in conduit.

    Yes, two blacks should be fine. Black and red would be conventional, but not important.
     
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  16. Nogasmn

    Nogasmn Member

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    75 feet.
     
  17. ACAG

    ACAG Member

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    Thanks for all the input. I decided to go with 4 gauge THHN wire and 8 gauge THHN ground in 1 inch PVC schedule 40 conduit, to make pulling the wire easier. Luckily I can return the smaller wire to Home Depot.
     
  18. gogojoey123

    gogojoey123 Member

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    The gloss black HPWC is back in stock at Tesla Store, for anyone interested.
     
  19. Nogasmn

    Nogasmn Member

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    Perfect! Make sure you add like 10-15% extra length in wire. Take your time and it will be an easy project.
     
  20. ACAG

    ACAG Member

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    Did you have any problem getting the 4 gauge wire in the terminal block on the HPWC? I was planning on using ferrules to make it easier.... Also I will be entering the HPWC from the bottom.
     

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