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NEMA 14-50 - Sometimes 120 V

Discussion in 'Charging Standards and Infrastructure' started by dhrivnak, Sep 29, 2011.

  1. dhrivnak

    dhrivnak Active Member

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    This may be old hat to many of you but is it common for campground NEMA 14-50 to be 120V? I stopped at my first KOA and was disappointed to find the old style UMC 240 did not work. When I pulled out my meter it appeared that the plug was only 120V. If I measured between the two hots the voltage was 0 and 120 between a hot and neutral. I tried several sites with the same result.

    Now the really quirky thing was I later stopped at a second camp ground and again they only had 120V NEMA 14-50 and my UMC 240 worked. The display on the Tesla said 240V and 30 amps but my meter said 0 volts between the hot legs and 120V between a hot and neutral. Was I just over tired and made a mistake or can the UMC 240 use a split legged NEMA 14-50 and charge like 240?

    I had installed my own NEAM 14-50 for charging in my garage and I had just thought all such plugs were 240V. But in looking at several old posts several other have seen NEMA 14-50 at 120V.

    By the way both campgrounds said they had NEMA 14-50 but had no idea if it was 240V.

    Thank you
     
  2. donauker

    donauker Member

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    I have been to quite a few campgrounds and have never seen this type of wiring of a NEMA-1450. It would be usable in a partial sense but most of the newer large motorhome owners would consider themselves cheated if they paid for a 50 amp site and were given one of these sites. This is how the RV TT-30 to NEMA-1450 adapter is wired and the larger coaches will detect this and automatically limit themselves to 30 amps of 120 volt load, thus making it no better then if they were in a 30 amp site.
     
  3. Doug_G

    Doug_G Lead Moderator

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    Usually they would put two different phases on the pins, but some of these places must have wired it up with the same phase on both pins. I'm sure it's not code, but for many RVs that don't draw a lot of power and only use 120V appliances they would probably never notice.
     
  4. TEG

    TEG TMC Moderator

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    I think that is what you would get if one of the two breakers behind the 14-50 was tripped.
     
  5. ChargeIt!

    ChargeIt! Member

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    Because of your second "quirky" experience ... where the UMC worked ... I'd have to ask whether your DVM was set to the correct settings (it's happened to me a few times, especially when tired). Certainly campsite mis-wiring could have been the cause, but less likely at two places. Single sided tripped breaker, also possible, depending on the type/age of the breaker/equipment.
     
  6. TEG

    TEG TMC Moderator

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    #6 TEG, Sep 29, 2011
    Last edited: Sep 29, 2011
    Plus, as I have said a bunch of times, campgrounds can use the NEMA14-50 in odd ways. Some RVs and trailers will use "dogbone adapters" to just get 120V from the 14-50, so they could provide only 120V service on the 14-50 (like you noticed) and still some of the RVs would find it useful.

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  7. dhrivnak

    dhrivnak Active Member

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    I was definately tired.

    I know the problem was not half the circuit breaker tripped as it was a double breaker. It will likley be a long time before I need this again and will just need to be prepared. And who knows after 500 miles and late at night I could have had my meter set wrong. But it did work for me.
     

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