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PSA - periodically replace your NEMA 14-50 outlet

Discussion in 'Model S: Battery & Charging' started by Doug_G, Dec 19, 2016.

  1. Doug_G

    Doug_G Lead Moderator

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    It has been mentioned on this forum that the NEMA 14-50 isn't designed for repeated plugging and unplugging.

    For the record, it doesn't matter if you plug and unplug it. They don't last. I've maybe unplugged my NEMA 14-50 half a dozen times since buying the car four years ago. And look what I discovered this week:

    IMG_5926.JPG

    I'm going to replace the plug right away... but I think I'll replace it with an HPWC.
     
    • Informative x 4
  2. Altes

    Altes Member

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    wondering if it would happen if you first turn off the breaker before plugging in (of course this might transfer the need to replace the breaker!!). Most of the 14-50's ive seen are black and so maybe they don't show the discoloration from the arc when the connection is made
     
  3. Doug_G

    Doug_G Lead Moderator

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    I noticed this because of the smell... the connection was slowly cooking.

    Power is off when you unplug from the car. The switch won't do a thing. (It's actually pretty stupid that it's installed at all on a NEMA 14-50... but at least now I can switch to Wall Connector and still be code compliant.)
     
  4. MP3Mike

    MP3Mike Active Member

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    #4 MP3Mike, Dec 19, 2016
    Last edited: Dec 19, 2016
    Technically you are replacing the 14-50 socket/outlet, not the plug. (The plug is on the adapter for the UMC.)

    From the title I thought you were talking about the adapter on the UMC, and I was wondering if there was going to be another recall.
     
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  5. gregd

    gregd Active Member

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    Did it also damage the pin on the charger's plug?

    Also, I recall there was another thread somewhere about different quality 14-50 sockets; some intended for single-digits plug cycling, e.g. behind a built-in oven, and others intended for multiple cycles, e.g. to service an RV. I don't know how to tell the difference, however, when looking at or asking for the part...
     
  6. Skipdd

    Skipdd Member

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    Thanks. I'm going to go check mine now. I have to reset the amperage in the car to 40, Periodically we get power hits that cause you the circuit to drop back to 30. Yet another reason to check the receptacle..
     
  7. mknox

    mknox Well-Known Member

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    I've been using my 14-50 for almost 4 years now with no problems. I did replace my UMC with a HPWC, but I actually installed a stove cable set to it and still plug it into the 14-50.
     
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  8. Saghost

    Saghost Active Member

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    Wow!

    Any idea what the physical mechanism behind this is, if you aren't unplugging?

    I thought this sort of failure was normally driven by the clamping springs losing tension from repeated cycling?
     
  9. youlikeadajuice

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    Doug, thanks for the PSA! Do you typically charge at 40 amps? Have you ever replaced the UMC or any of the adapters or is this all original?
     
  10. Doug_G

    Doug_G Lead Moderator

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    I had been charging at 40 amps. I backed it down very recently. I had gone out to the garage late in the evening to drop some recycling in the bin... and sniff sniff... hmmmm.

    Yes the UMC has been replaced a couple of times. It was the leading cause of unplugging the NEMA 14-50. I had trouble with the connector at the other end; root cause was the charge port damaging it somehow. Once they changed the charge port the problems went away.

    Car is going in for annual service (was supposed to be today, now tomorrow). I'm asking if they can sell me a wall connector and toss it in the car.
     
  11. Haxster

    Haxster Member

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    I'm not an electrician, just an EE. But I suspect that this may have been caused by a poor connection at the socket. If the connection isn't tight and the resistance is high, it gets hot. At 40 amps, it only takes .06 ohms of resistance to produce 100 Watts of heat. (W=I*I*R).
     
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  12. mknox

    mknox Well-Known Member

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    This is most likely the cause. These outlets were typically designed for intermittent loads. Ranges/Stoves will cycle on and off and generally won't be pulling their full rated load for hours on end. The high power, steady loads that EVs pull while charging for hours on end will generate problems like this that you likely wouldn't otherwise see.

    It's probably not a bad idea to periodically check your breaker panel and make sure the wires are properly torqued to the breaker as well. The last time I was in my panel, I checked all of my branch circuit breaker connectors and was shocked (no pun intended) to see how loose some of them were.
     
  13. Naonak

    Naonak Member

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    It's interesting that you found this... because I found this just the other day (Tesla replaced it at no charge)

    I thought the grey connectors were suppose to be the non-faulty ones. Guess that wasn't right. That is from a 14-50 adapter, too.

    You could always buy a second 14-50 UMC adapter and leave the base plugged in to your outlet... then you won't have the insertion issues. If you needed to replace the UMC 14-50 adapter, that would be a lot easier, though a bit more costly, but not by much.
     

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  14. jbcarioca

    jbcarioca Active Member

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    There are also 14-50's that are designed for heavy plugging/unplugging, as those typically deployed in hospitals and RV parks. At one of my frequently-used hospital buildings the free EV charging is on 14-50's that were installed several years ago and have been used multiple times per day ever since. They are as robust as they should be.

    I suggest that anybody wanting to use a 14-50 at home replace the plug and receptacle with heavy-duty units that are designed for continuous high amperage loads. I am not certain where these are to be found but Any electrician who's worked around hospitals and RV parked ought to know.

    In theory they all should be the same. In practice we know they are not.
     
  15. brucet999

    brucet999 Active Member

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    Looking at your adapter pic, it occurs to me that OP's 14-50 outlet may not be the problem, but rather the 14-50 adapter overheating one pin and the transmitted heat cooking the plastic face of his 14-50 outlet.
     
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  16. miimura

    miimura Active Member

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    I prefer this style socket to the one pictured by the OP. I don't know if the number of rated insertions is any higher though. I also pull out the socket and check the screw torque on the wires annually.

    NEMA 14-50 Surface Box_r.jpg
     
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  17. AWDtsla

    AWDtsla Active Member

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    Get a higher quality receptacle. There's one specifically recommended, it's definitely not the one in post 1.
     
  18. Joe F

    Joe F Member

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    Hubbell HBL9450A
     
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  19. Skipdd

    Skipdd Member

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    I checked - mine appears ok. Mine looks more like the one posted by @miimura. Also I bought a spare charging cable kit, so I could carry a full kit in the car; I keep my original UMC plugged into the outlet all the time. Still, after reading the posts, I think I will ask my electrician to check the wires annually as was suggested. I keep all the other key systems in the house well maintained, so I will just add this to the list..
     
  20. apacheguy

    apacheguy S Sig #255

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    I have the same symptom shown in the picture appearing on mine. Will have service look at it next time.
     

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