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Any Issues with GFCI breaker and Tesla UMC?

Discussion in 'Charging Standards and Infrastructure' started by hingisfan, Jan 20, 2015.

  1. hingisfan

    hingisfan hingisfan_Mark_V

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    I saw a couple threads from a few years ago, just wondering if people are using GCFI breakers now, and if so, are you experiencing any issues with the UMC?

    (NEMA 14-50 outlet)

    Thanks!
     
  2. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    See this post from FlasherZ, the resident TMC expert on such issues: NEMA 14-50 outdoors

    As far as I know, no one makes a GFCI 14-50. OTOH, the UMC and the HPWC both have GFCI's built in.
     
  3. hingisfan

    hingisfan hingisfan_Mark_V

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    I have one now in my panel (50 amp), for my hot tub.
     
  4. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    While no one makes a GFCI 14-50, you are very correct that it is possible to buy a 50 Amp GFCI breaker. The typical "hot tub", GFCI breaker and the GFCI in a UMC check the balance of current across the two Line wires, but to do a truly, all-possibilities, 14-50 GFCI, it needs to check the balance across the two Lines and the Neutral in a 14-50, combined. I do not know of such a product. If you do, please send a reference.
     
  5. sbanks

    sbanks Member

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    I use a 50 amp GFCI circuit breaker feeding the NEMAN 14-50. I'm not concerned about a shocking hazard from the UMC but from the 220 40 amp outlet when the UMC is not plugged in. Mine is outside and I want to protect against some kid sticking a nail in one of the hot contacts.
     
  6. hingisfan

    hingisfan hingisfan_Mark_V

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    So, you aren't having any issues then? I had seen a few posts from the early Model S days that said people were running into trouble with the UMC running on a GFCI breaker.
     
  7. tga

    tga Active Member

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    Probably not a bad idea. I had a similar concern with my solar installation. The disconnect switch on the outside of my house connects the array to the unfused mains (a supply side connection on the utility side of the main breaker). I put a lock on the box so an inquisitive kid walking through the yard couldn't open it, poke around inside, and get zapped.
     
  8. bonnie

    bonnie Oil is for sissies.

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    You're probably recalling discussion about charging the Roadster on 110v using the supplied cable (which has a GFCI). When coupled with an outdoor outlet similarly equipped, odds are high it would double fault. So Roadster owners (myself included) have modified the supplied cable and removed the GFCI.
     
  9. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    I looked this up, and the 2-pole 50 Amp GFCI's do protect all three wires L-N-L as a set for balanced current (no leaks to ground). Here is one example: Siemens QF250 50-Amp 2 Pole 240-Volt Ground Fault Circuit Interrupter - - Amazon.com, and it's schematic showing the three wires going through the sense transformer.

    2-pole GFCI.png
     
  10. tga

    tga Active Member

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    • Informative x 1
  11. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Nice reference! Thanks.

    All the GFCI's that I have torn apart and looked at have a current transformer that measures the difference current (leaks to ground). The transformer multiplies the current that is fed to a small circuit board that rectifies the multiplied, difference current to trip the circuit interrupter.
     
  12. hingisfan

    hingisfan hingisfan_Mark_V

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    So....I already have a GCFI 50 amp breaker in place (used to be hot tub). Should I use this? Or swap it out for a non-GCFI? Potential for issues with UMC or no?
     
  13. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    I'd just use the existing GFCI breaker. It probably will work fine, but if it gives you trouble, you could switch it to a non-GFCI because the UMC has one also.

    Good Luck! Either way, please report your results.
     
  14. tga

    tga Active Member

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    +1 - can't hurt to try it as is. I see no need to put a new breaker in "just in case."

    If you do wind up changing it, you might want to throw the old one on Craigslist or ebay. A 50A non-GFCI is around $10 @ Home Depot. GFCI's are around $100.
     

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