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Thread: 30 Vs 50 Amp

  1. #11
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    Quote Originally Posted by fez111 View Post
    You are absolutely correct. There is a grounding conductor on the periphery of the female plug that connects into the RV socket. We use a double 90 degree dog bone to connect so the cables hang straight down.

    Also, you are correct in that two 50 amp circuits = 100 amps total capacity...as long as they are wired correctly to two different phases of the incoming power. If the various loads are distributed as equally as possible between the two busses than the individual amperage should not exceed the 50 amp per phase capacity.

    When forced to connect to a 30 amp source the two hot leads are jumpered together inside one of the plugs.

    One other thing to mention... In a 50 amp RV circuit each hot lead is sized to carry 50 amps each...but the neutral is the same size. The reason that the neutral conductor can carry the full 100 amps load is because the two 50 amp phases are 120 degrees apart electrically which causes the current for two phases passing together through the neutral together to effectively cancel each other out. Every house wired with 220 volts is wired the same way.
    Thank you. This makes sense. I set up a plug at home to keep the RV plugged in, and only ran a 10-2 wire, assuming that I could leave one leg void of power. I had read that a 4-3 adapter, like the one we can use in a campground when only 30 amp single phase is available, simply drops one of the hot legs. I was wrong. The adapter clearly does more than just drop a leg. I reran 10-3 with 2 hot legs and bingo, everything works fine now.

    As I said earlier I know just enough to get myself in trouble. But your response does clear a lot of this up. And yes, when I look at the plug, it is obvious that the ground in on the outside of the connector. Thank you
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  2. #12
    Paid my dues 😁 FT4NOW's Avatar
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    Quote Originally Posted by DalePatterson View Post
    Thank you. This makes sense. I set up a plug at home to keep the RV plugged in, and only ran a 10-2 wire, assuming that I could leave one leg void of power. I had read that a 4-3 adapter, like the one we can use in a campground when only 30 amp single phase is available, simply drops one of the hot legs. I was wrong. The adapter clearly does more than just drop a leg. I reran 10-3 with 2 hot legs and bingo, everything works fine now.

    As I said earlier I know just enough to get myself in trouble. But your response does clear a lot of this up. And yes, when I look at the plug, it is obvious that the ground in on the outside of the connector. Thank you
    Did you use a 30A breaker at your home plug? 10/3 is only rated for 30A. The wiring inside your RV from the shore power connection to the breaker box uses 6/3 since it is 50A service.

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  3. #13
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    Quote Originally Posted by fez111 View Post
    You are absolutely correct. There is a grounding conductor on the periphery of the female plug that connects into the RV socket. We use a double 90 degree dog bone to connect so the cables hang straight down.

    Also, you are correct in that two 50 amp circuits = 100 amps total capacity...as long as they are wired correctly to two different phases of the incoming power. If the various loads are distributed as equally as possible between the two busses than the individual amperage should not exceed the 50 amp per phase capacity.

    When forced to connect to a 30 amp source the two hot leads are jumpered together inside one of the plugs.

    One other thing to mention... In a 50 amp RV circuit each hot lead is sized to carry 50 amps each...but the neutral is the same size. The reason that the neutral conductor can carry the full 100 amps load is because the two 50 amp phases are 120 degrees apart electrically which causes the current for two phases passing together through the neutral together to effectively cancel each other out. Every house wired with 220 volts is wired the same way.
    On standard North American split-phase 120/240 service, the legs are 180 degrees out of phase which means the average neutral current is 0 if both legs are equally loaded. Maximum neutral current is 50A in an RV circuit if one leg is fully loaded and the other has no load.

    Phases 120 degrees apart is what you see on 3 phase service where the typical non-industrial service is 208V line to line and 120V line to neutral. You have the same neutral average current being zero with the phases having zero load.
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    Quote Originally Posted by FT4NOW View Post
    Did you use a 30A breaker at your home plug? 10/3 is only rated for 30A. The wiring inside your RV from the shore power connection to the breaker box uses 6/3 since it is 50A service.

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    Yes, 30 amp breaker. 10 gauge was expensive enough! We plug it in to keep the battery charged, and move the slide in/out packing it. It only has one AC unit, so even running that I cannot imagine a scenario where 50 amps would be required.
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    If I'm not running the AC, I just use a large extension cord from a wall plug with the correct adapter at the 5W. Fridge works fine along with other items except the microwave...
    My solar keeps the batts fully charged.
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    Quote Originally Posted by DalePatterson View Post
    Yes, 30 amp breaker. 10 gauge was expensive enough! We plug it in to keep the battery charged, and move the slide in/out packing it. It only has one AC unit, so even running that I cannot imagine a scenario where 50 amps would be required.
    What breaker did you hook this new 10AWG up to? Hopefully it was a 2-pole 30A CB. So are you saying that you wired it from the panel to a receptacle rated 50A 250V? If so then you're still only going to have 30A available on each leg, not 50A. Keep in mind that with a 30A 120V power supply you have a max of 3600 Watts available for use. 30A x 120V = 3600W.
    On a 50A 120/240V power supply you have
    50A x 120V = 6000W
    + 50A x 120V = 6000W for a total of 12,000 Watts available to use.
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    Quote Originally Posted by IBEW Sparky View Post
    What breaker did you hook this new 10AWG up to? Hopefully it was a 2-pole 30A CB. So are you saying that you wired it from the panel to a receptacle rated 50A 250V? If so then you're still only going to have 30A available on each leg, not 50A. Keep in mind that with a 30A 120V power supply you have a max of 3600 Watts available for use. 30A x 120V = 3600W.
    On a 50A 120/240V power supply you have
    50A x 120V = 6000W
    + 50A x 120V = 6000W for a total of 12,000 Watts available to use.
    Yes, 2 pole breaker, 30 amps with 10 gauge wire, 2 hot legs, a neutral and a ground. Yes, the camper is rated at 50 amps, but in my wildest dreams I cannot imagine using that much juice for a few lights and to charge the battery in my driveway. If I ever do, I assume the 30 amp breaker in my garage will trip and I'll know it. (We camped this past weekend and only had a 30 amp single pole service, ran the AC, fridge, lights etc and had no issues). I'm also assuming the camper is rated at 50 amps in case I decide to add a 2nd AC unit. Everything is pre-wired and the hole is even cut. This way you can just add the 2nd AC unit and not have to rewire the entire thing. But that is just my guess....
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    Quote Originally Posted by DalePatterson View Post
    Yes, 2 pole breaker, 30 amps with 10 gauge wire, 2 hot legs, a neutral and a ground. Yes, the camper is rated at 50 amps, but in my wildest dreams I cannot imagine using that much juice for a few lights and to charge the battery in my driveway. If I ever do, I assume the 30 amp breaker in my garage will trip and I'll know it. (We camped this past weekend and only had a 30 amp single pole service, ran the AC, fridge, lights etc and had no issues). I'm also assuming the camper is rated at 50 amps in case I decide to add a 2nd AC unit. Everything is pre-wired and the hole is even cut. This way you can just add the 2nd AC unit and not have to rewire the entire thing. But that is just my guess....
    You are probably correct about the 2nd AC wiring being installed... everything should be done if it was included in your package. I know when Grand Design preps for a future second AC unit they frame the opening, run the wire from the CB to the ceiling, and the T-stat wire down inside the wall by the bedroom light switch. You will be fine with the power setup you have at your driveway...I always keep my RV plugged into a standard 30A 120V RV receptacle while at home. Fridge stays on, battery is charged, and AC is used from time to time. With your setup it depends on what RV appliances are on each "30A hot leg" in the RV to determine what you can and can't run simultaneously. You could possibly run an AC unit, water heater, together along with the fridge, the converter and other items in your RV. Enjoy your RV!
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  9. #19
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    Quote Originally Posted by DalePatterson View Post
    Yes, 2 pole breaker, 30 amps with 10 gauge wire, 2 hot legs, a neutral and a ground. Yes, the camper is rated at 50 amps, but in my wildest dreams I cannot imagine using that much juice for a few lights and to charge the battery in my driveway. If I ever do, I assume the 30 amp breaker in my garage will trip and I'll know it. (We camped this past weekend and only had a 30 amp single pole service, ran the AC, fridge, lights etc and had no issues). I'm also assuming the camper is rated at 50 amps in case I decide to add a 2nd AC unit. Everything is pre-wired and the hole is even cut. This way you can just add the 2nd AC unit and not have to rewire the entire thing. But that is just my guess....
    When at our home I run my 50 amp rv on my 30 amp 4-wire dryer outlet with an adaptor that connects the 2 hots, neutral and ground properly. I can run both AC units since they are connected to opposite legs. I monitor current on each leg with our EMS and I never exceed 24 amps on either leg.

    Be careful using some adaptors that are designed for Teslas because they don’t connect either the ground or neutral.

    Here are 2 that claim all 4 wires are connected

    https://www.amazon.com/CircleCord-Ch...dp/B08XNX8KQ6/

    https://www.amazon.com/Rophor-Charge...dp/B09SHXVGBY/
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    Found this thread while seeking info on 30 vs 50 amp...we are currently camping and are having power issues with the 50 amp connection at our site. EMS kicking out regularly. Showing as low as 98 volts on one leg at one point. So I adapted to 30 amp and plugged into that. Worked ok Friday, then voltage dropped and EMS started kicking out. Campground maintenance comes out and their solution is to plug into my neighbors's pedestal on 30 amp (neighbor is using 50 amp) and they would do a permanent fix after the holiday weekend (we're here for the month). Worked for several hours then voltage dropped again and EMS kicking out. Problem lets up in the evening through early morning then voltage drops again. Called maintenance again yesterday and, well, they never showed up.

    My panel looks as thought half of the trailer is on one leg and half on the other. The 50 amp breaker is in the middle and there are breakers above and below it, but there are 2 breakers for the fridge...one on one side and one on the other. Soooo, my question is, when I am working on 30 amp using an adapter, how does this power those two sides? Am I limited to 15 amps per side? My EMS shows draw on both legs occasionally while on this 30 amp setup.

    Thanks in advance for taking time out of your holiday weekend!
    Jeff & Sherry
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