Sunday, December 9, 2018

30 to 50 Amp Adapter?

Forum Index Technical Forums General RV electricity 30 to 50 Amp Adapter?

This topic contains 19 replies, has 10 voices, and was last updated by  James Knoch, Jr. 2 months ago.

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  • #78898

    skyjim
    Participant

    I’ve been using a 30 to 50 amp adapter for years when we were parked without 50 amp service. I was recently told that this is not a good idea. Any electrical “gurus” have input on this subject?

    Thanks in advance

    Jim

    • This topic was modified 48 years ago by .
  • #78969

    Monarch
    Participant

    I’m not a guru, but at home I use a 15 amp adapter to connect my 30 amp travel trailer to my house electricity. Also, I have a 50 to 30 amp adapter in case a site has no 30 amp service.

  • #80606

    Gary Pellecchia
    Participant

    Shouldn’t be a problem so long as you’re not expecting to get 50A out of it. Basically the adapter is going to double the one 120V lug from the 30A service. If you try to pull more than 30A combined through the two lugs (like running both air conditioners at once) then you will probably trip a circuit breaker at the service hookup.

    • #80792

      Wolfe Rose
      Participant

      I believe Gary here is correct… Except that you also need to understand that “50 amp” RV cords have TWO 50@120V leads versus a single 30A@120 for 30 amp service… Which means the difference of 12,000 Watts vs 3,600 Watts. This could be extremely challenging for high-wattage RVs to avoid popping breakers. While very rare(?), if you have any actual 240V appliances installed in the RVs, the two hots tied together will produce zero voltage and that appliance would not work at all.

  • #80720

    Dave Telenko
    Participant

    I did read something about using the 50 to 30 amp adapter. We just traveled 8000 miles doing the ALCON highway & we stayed in a lot of places in Canada & Alaska & very few had 50 amp service. Most remote places only have generator service at best, so getting 30 amps was great!

    Snoopy

  • #80733

    Lanerd
    Participant

    Care to share “who” told you this?

    • #80740

      Dave Telenko
      Participant

      Hi Lanerd, not sure of your question, if its about the 50/30 amp issues. I think it was in RV travel, but i don’t recall the details about why is wasn’t a good idea to use an adapter. Perhaps another reader can recall. It could have possible been Mike Sokol our RV electric guru!

      Dave

  • #80768

    jkoenig24@gmail.com
    Participant

    How else would you get ANY electric service out of said pedestal? It’s NOT a good idea to “stack” adapters (ie 50A > 30A > 15A). I have separate 50A > 30A and a 50A > 15A. EACH extra connection will add additional voltage drop (something you want to avoid as much as possible).

    • #80770

      Dave Telenko
      Participant

      I totally agree! I wonder what Mike Sokol would have to say about using the 50/30 adapter?

      Dave

      Thanks

      Dave

  • #80774

    skyjim
    Participant

    I think I saw it on RV Travel….

  • #80788

    Mike Sokol
    Participant

    Gosh, I was waiting for my name to be said 3 times like Beetlejuice…

    A 30-amp to 50-amp adapter or even a 15-amp to 50-amp adapter is OK as long as you realize the wattage limitations. There’s a big step down in power since a 50-amp service is actually 100-amps at 120 volts. So instead of 12,000 Watts from a 50-amp outlet, you only get 3,600 Watts from a 30-amp or 2,400 Watts from a 20-amp outlet with a 15-amp adapter. The only real danger would be using a cheap orange extension cord on the 15-amp adapter since your 20-amp current draw could far exceed the 13-amp capacity of many cheap cords. And that could cause a fire. Y-adapters are something else entirely which need their own thread.

  • #80816

    Thom Sloan
    Participant

    I am a RV tech. And owner of T&A RV,

    When plugging in your 50 amp trailer or moter home into a 30 amp using a adapter you nead to act like a 30 amp rv , that means only 1 ac, water heater on lp, and no extra appliances,  if using the microwave you have to turn off the ac 1st, now the why? When it is 100 degrees on the roof the ac draws about 20 amps, Ouch!, a electric water heater draws 12 amps, a microwave draws 12 to 15 amps, A rv refer draws 7 to 9 amps, a rv with no appliances turned on draws 7 to 14 amps, time to do the math, using a 15 amp adapter should never be used except to keep the battery charged, and never use a extension cord with a 15 amp adapter,  remember your RV maybe your home but it is not a house with 200 amp at 240 v. Service , and please check your voltage, the lower the voltage, the higher the amperage draw, Thanks, Thom

    • #80844

      Mike Sokol
      Participant

      Thom, ref your statement “and please check your voltage, the lower the voltage, the higher the amperage draw”, I don’t think that’s true. This seems to be an old-wives tale based on the fact that AC-DC motors do indeed draw more current as the voltage is reduced, which reduces their RPM, which reduces the back EMF. Certainly, resistive loads don’t behave that way. Reduce the voltage going to a hair dryer, and the amperage goes down as well. And I don’t think AC motors in an air conditioner compressor behave that way either. Now if they’re under load they can reduce their RPM as their magnetic field begins slipping due to the too low current from the too low voltage. And I think that’s what causes compressor overheating, etc…

      The only thing in an RV that could possibly draw more amperage at lower incoming AC voltage would be intelligent switching power supplies in your laptop computer, 12-volt DC converter, and any other “small” electronics using switch-mode supplies. Now, an air conditioner running at low voltage will be producing much less cooling effect, which will force the compressor to run longer. But that’s more KWH, not straight amperage draw.

      So am I missing something? If someone has a white paper or  empirical data demonstrating why an RV could draw more current as the voltage goes down I would love to read it. And I can certainly call the engineering department at an RV air conditioner manufacturer to ask for data as well.

      Hypothesis please…

      • #81162

        Mike Sokol
        Participant

        I don’t have a definitive answer yet on low voltage causing increased current draw from an AC induction motor, but I’m also the moderator on the AC Power & Grounding forum on ProSoundWeb.com. The initial consensus is that the amperage WON’T go UP as the pedestal voltage goes DOWN. This is looking at the physics of induction motor theory, not empirical data yet. I’ve already sent in inquiry into engineering at Dometic so I’ll update you all later with my findings. I’m looking for hard data, NOT guesses.

  • #80820

    James Knoch, Jr.
    Participant

    The 30A to 50A adapter is fine to use as long as you don’t try to draw more than 30 Amps total between both hot legs of the RV’s 50A distribution system. If you do draw near 30Amps total, there may be some heating, especially if the pedestal contacts (or the adapter pins) are worn or pitted. Obviously, if you draw more than 30A, even briefly, you will trip the pedestal breakers.

    FYI, I suppose I am an electrical guru … licensed electrician and I retired after 37 years as the Lead Distribution Electrical Engineer for the local power company.   Swampy

  • #80826

    skyjim
    Participant

    James K, Thom S, and Mike S.

    Great answers!

    Thank YOU ALL!

    That’s just the kind of information I needed and wanted.

    Guess I’ve been doing OK after all….

    Thanks again

    Jim A

  • #80894

    Thom Sloan
    Participant

    Hay Mike, I will try to get the white sheets for you , Dometic and Coleman teach this plus we shone the effect in RV school,  I seen a brisk air draw 26 amps at 114 volts , Thanks,  Thom

    • #80895

      Mike Sokol
      Participant

      Thom,

      Excellent. Remember, I’m looking for run current at low voltage. I know that startup current at low current will go sky high due to the longer time the starting capacitor is engaged before the start switch opens up.

    • #80896

      Dave Telenko
      Participant

      Hi Thom, tell us more about RV school, I didn’t even know there was  even one of those! I’m one of those RV’s that like to know what, how & when things happen. I’m a forensic machinist so to speak as I’ve been a machinist since forever. I really enjoy getting to the bottom of a problem & fixing the problem! I know just enough about electricity to keep asking questions. I’ll never forget the time I hooked up a knife switch in our cellar for a light & when I engaged it, I got knocked on my keester, I was only 10 at the time.

      Dave

       

  • #81166

    James Knoch, Jr.
    Participant

    Mike, As part of my utility’s load management program, as demand approached over 100% of system capacity, The auto-regulators at the bulk substations were adjusted to lower the High Voltage by a few percent as an effort to reduce demand. The second level contingency would be rotating load shed (Rotating black outs) until the system demand was substantially reduced to a safe level. I have seen the results of the lowered High Voltage and there was an actual demand drop on the system (to my surprise since we were experiencing extremely hot weather at the time). Relating this to the question at hand, lowering the Voltage a few percent actually caused a drop in demand, vis a vis, consumer appliances continued to function as designed. The demand reduction was likely not from the rotating equipment, but from the resistive loads.  ……. Jim

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