Reader Interactions


  1. Can you believe that as an RV Park owner I’ve seen electricians and others use these meters hundreds of times but I find it difficult to keep in my mind how the readings should look on each hole. I have copied this picture and am pasting one on my wall for handy reference. Thanks

  2. My understanding is that 240 volts are not allowed in RV’s. I understood that both hot legs are on the same phase, therefor a measurement between them would show zero volts. The benefit of the two hot legs would be actually more than 50 amps available, but only 120 volts. Am I wrong ?

  3. Rather than 240 being “not allowed”, I’d say it is more likely that 240 V is not commonly used. Even in a stick house the 240 V is only used for a dryer, electric range, and maybe in the garage.

    I believe an RV park which wires the plug so that each hot was the same phase leg would not be wired to code for that connecter.

    But just because you would have 240V on the RV Park pedestal doesn’t mean you would see 240V in the RV unless the RV manufacturer wired the hots such that you would have a 240V plug in the RV. Now individual 120V circuits may have different hots they get their power from, but you should never care about that for most practical purposes.

    I would also think that if both hots were the same phase I would actually wonder if they were off different breakers somewhere.

    For a properly wired 50A plug I’m pretty sure it will show 240 V.

    You are correct that you get TWO (not ONE, but TWO) 50 Amp 120 V circuits for a total of 12,000 Watts of power. This is substantially more than the 30A plug which would only provide 3600 Watts.

  4. If you plug your RV into a plug that shows as you have in your diagram for 240v, you will smoke most if not all appliances on the circuit in short order. At an RV 50 amp plug in you should see 0 volts across the 2 hot legs of 120. You should see 120 volts from each hot leg seperately, metering hot leg to ground or neutral.

    The metering diagram shows household 240v, and this is why you can not plug your RV into house dryer plug etc.

    Forget PHASE, that term should be left out unless you start delving into 3 phase power. It’s split phase. For simplicity and non 3 phase discussions, just use LEG.

    To explain – 240 comes out of transformer, it’s split in half via earth. Check out transfer diagrams to see how 120 achieved.

    Per each RV hook up spot, RV parks only use one leg of 120 from transformer, this is why when you meter across the 120 volts hot legs you should see zero.

    It’s not proper or improper per say it just needs to be understood how it works for intended application.

    As a thinking handyman, fabricator and general tinkerer of anything I get my hands on, I was curious when I bought a 30 amp 27′ TT and needed more power and so this is what I figured out.

    So on a 50 amp RV, in the RV 1/2 of the load is on one side of the 120 volt circuit and 1/2 of load is on other side of circuit. But it all comes from one leg of 120 from the transformer.

  5. Thanks Brandon. I agree with everything you say except one thing. Why would you smoke most of your appliances? The reason I ask is because there should never be hot-hot connections – ergo never getting 240 on an appliance. In the same way, if a hot-hot connection in your single transformer connection occurred, you’d get 0VAC. So your appliance wouldn’t work either.

  6. Hey Marlan you are correct. My original post needs to be corrected / edited.

    So an RV park 50 amp plug in outlet will show either 0 volts across the 2 legs or 240 volts across the 2 legs. It will show 240 volts, if, when wired they used the other leg from the transformer. As long as get you 120 from each leg to neutral you are good to go.

    Household 240 dryer or maybe stove will be fine for 50 amp rv service if put in matching male or female receptacle.

    The issue of smoking appliances is for 30 amp rv service. The other leg is neutral. If the 2nd leg is energized with 120 it will then be completing a 240 volt circuit. That is where people have gotten into trouble. Attempting to plug in or switch out dryer or stove plugs. They hook up both legs of 120 instead of switching top leg to neutral.

    One thing that strikes me as incorrect, as I’ve seen elsewhere in other forums, others claim 50 amp service is actually 2 legs of 50 amp service.
    All wiring I see for 50 RV stuff is 6/3. 6 gauge is good for 50 maybe 60 amps. I’m not sure how are why that myth persists.

  7. Additionally it should be clarified that stove / dryer wiring at house for 50 amp rv is temporary to turn on some lights etc. one should not camp / live in camper with this wiring set up because most dyer / stove and wiring is not of sufficient sizing and capacity to run 50 amps and should be reflected by the house breaker for that circuit.

    If 30 amp RV and wired to dryer or stove with at least 30 amp breaker in house, PLUS plug properly wired, that will work fine.

  8. Brandon, for power to be excepted by my RV, the 50amp receptacle has to be wired with 4 wires. 2 hot wires, a ground, and a neutral. On a 3 wire 240V receptacle, you will have 2 hots and a ground. I’m not sure where the 240V is split down to (2) 120V circuits in most RVs but in mine, I believe it takes place in the Power Manager.

  9. Marlan, I agree with each reading on each meter as shown in your diagram. For the RV 50amp to work properly though on my RV, and I suspect any 50amp RV plug, if you checked the top prong of the receptical to either of the hot prongs, you should get 120V.

  10. What i would like is a schematic from the breaker to the juntion box to the rv. Thats the part which may be confusing the conversation i just bought a 14 dynamax 3650RL and havnt figured out how to get 2 legs of 120 without running 2 100w legs with a common neutral to a duel 50w plug to the rv. Is this correct? All other options would provide the dryer 50w/250v direct wire, which is what would burn up my rv electrical.

  11. Robert – I’m going to do a little more research on this most very interesting question and see if I can get a true schematic that the RV mfg work from.

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