50 AMP and 30 AMP: What’s the difference?

In Motorhomes, there are 3 kinds of AMP services: the 50 amp, 30 amp and 20 amp. But let us just focus on the 50 and 30 amp as they are the most common ones. Traditional motorhomes where designed having the 30amp service while modern-day RVs generally have 50 amps which are more preferable as they can accommodate more loads than the 30 amp.

So which is better the 50 amp or the 30 amp?

Learn more from  RVgeeks

Here is what Utility Supply Group has to say.

Do you have any tips for new RVers on using 50 amp or 30 amps?

34 COMMENTS

  1. 20 amp plug as shown is actually a 15amp plug.
    A true 20 amp plug has one prong running up/down, and the other running sideways.
    A 15 amp cord can be used in most 20amp sockets, but a true 20amp cord can only be used in a 20 amp socket!

  2. 50 AMP service is actually 240 volt service on a 50 Amp breaker. It gets divided into two 120 vold circuits inside the RV producing the 12,000 watt capacity as long as the draw on the tow sides is balanced. Amps x Volts = Watts.

    • That is incorrect! If this were true you could plug into a drier or welder socket. 50amp RV circuit is 2x120volt from the panel.

      • The other thing I would disagree with is 50 amp is more efficient. Since you are running anything on 240 volt, it doesn’t change the efficiency. What it does is give you more capacity. My understanding is the other 120 volt side is pretty much just for the additional AC unit and washer and dryer hookup. The rest of the coach is on the main 120 volt leg. That way if you are on a 30 amp 120 volt receptacle, you don’t lose any lighting, heating, or refrigeration circuits.

        • When a 240-volt service is divided into two 120-volt circuits then Ken Hill is correct, that all it does is provide additional capacity. However, a one-horsepower electric motor wired to run on 240-volts will be more efficient than a one-horsepower motor wired to run on 120-volts because doubling the voltage reduces the motor’s current draw. That does not of course apply to RVs; none of which to my knowledge utilize any 240-volt devices. Except for the largest all-electric diesel pushers, most motorhomes will never need or use more than about half the capacity of a 50-amp connection.

      • It is correct, a welder is 240 volt only, no neutral. Newer dryers are 120/240 volt but only 30 amp. The advantage of a 50 amp is more available usage in the rig. 2 ac’s can be used along with many more devices at the same time. 50 amp rv’s are the way to go. The rv user can always adapt down in amperage but must be mindful of usage in the rig.

      • Regarding Mike LeBlanc’s comment, the 50-amp connections at RV parks do, indeed, provide 240 volts with a center-tapped neutral conductor. That voltage is then divided by the RV into two 120 volt circuits. With a correctly-wired plug adapter a 50-amp RV plug can be safely plugged into an electric dryer socket but only 30-amps per side would be available. That is more than enough to fully power my 35-foot long Itasca Sunova motorhome with two rooftop air conditioners. If the campground power post supplied 2X 120 volts instead of the usual center-tapped 240 volts, the neutral wire could be severely overloaded.

    • it is 240 volts, and with the right adapter any 240 volt single phase appliance would work. there is 2- 120 volt circuits, a neutral ,and a ground. where people get in trouble is in the breaker panel they tie the 2 120 volt bars together which would work on a 30 amp circuit but if they plug into a 50 amp plug they shove 240 volts to appliance and smoke appears!

      • You cannot tie two 120v legs together in a panel, because they are out of phase. This would just be a shorted 240 circuit.

    • Our motor home has a 7000 watt Onan generator to use to power all of our onboard devices.
      2a/c , Res refrig, 3 rv’s, sattelite dome, etc. 50 amps service.

      • 50Amp shore power actually provides 100 amps of usability. You can use 50 amps off leg 1 and 50 amps more off leg 2. Whichever leg provides power at each outlet, air conditioner, TV, microwave, refridgerator, etc. etc. is determined by what you wire it too. In my rig, the 2 circuit breakers on the generator limit service to 35 amps on each leg when taking power from the generator. A 50 to 30 amp adaptor plugged into a 30amp power pedestal only gives you 30 amps total. That is to say, leg 1 and 2 when added together cannot exceed 30 amps. And yes there are adaptors that plug into both a 20amp outlet and a 30 amp outlet, I do not recommend them, they will provide 30amp service on leg 1 and an additional 20amp service on leg 2 — which gives you 50amp total service available. That is only half the power available with what you get on a true (double) 50 amp circuit breaker from shore power.

        • Question for you. If you measure AC voltage across those two 120v legs, do you see 240v or zero volts?

        • Not quite correct. A 50 amp service is limited to 50 amps. Any continuous use device is limited to 80% of the circuit ampacity by the National Electrical Code. A 50 amp rv could conceivably use 2 ea 120 volt 40 amp circuits inside the rig. A 50 amp rv circuit consists of a ground,neutral and 2 hots. Hot to neutral is 120 volt and hot to hot is 240 volts. The 20 and 30 amp receptacles are 120 volt only. Most rv circuits are limited to 120 volts as 240 volts will not be available on a 20 or 30 amp circuit if an adapter is needed. You will see a 15 amp duplex outlet on a 20 amp 120 volt breaker in most pedestals. This is allowed by the NEC, if it were a single outlet it would have to be a 20 amp outlet. The breaker or fuse inside the rv limits current draw no matter what ampacity receptacle the rv is plugged in to.

  3. I have a motorhome that requires 30amp, 120 volt service. In that 50amp service is 240volt what happens when I use a 50amp to 30amp adapter when 50amp service is the only option? Does the adapter pick up only one leg of the 50amp service? Obviously I don’t want to over energize my circuits.

    • Don Williams I did that with an adapter. The 30 amp wire overheats as it is not gauged for 50 amps. Prolonged use will melt the insulation on the wire creating shorts and worst. I was fortunate to just get shorted out. Cost me nearly $400. It was in the middle of summer both a/c’s were running. Blew transformer melted wires. A real mess.

  4. What a disparate collection of responses! Older RVs did not have the power consuming devices that more modern ones do and 30A was satisfactory for all needs. Many machines now have 50A plugs and if you use a 30A source with an adaptor you are likely to find that some things in the RV will not work. In such a machine the 240 volt power source is kept separate, delivering two 120 volt circuits which go to different things in the RV. Typically, the air conditioners are separated and operate individually from the two supply circuits. With 50 amp service you are actually getting two separate 120V power sources delivered to your RV. I installed a 30A outlet on the side of my house and used an adaptor to supply my 50A machine and all was well. I bought a new RV and discovered that 30A simply did not meet its needs. I installed a 50A outlet and all is well now. The question was “which is best?” and there is no “best.” Use what is appropriate for the circumstance.

  5. 30 or 50 amp refers to the maximum load that can be supplied. People need to think of it as 2 x 120 volt circuits. One breskered at 30 amp and one breakered at 20 amp. yes. There is 240 volts between the legs but most campers or motor homes only use 120 volt appliances. Most everything in a camper or motor home is wired off the 30 Amp side. The 20 amp side is usually used by a second air conditioner or heater. Neither is better. It’s all about what can be supplied. Adaptors that split the 30 amp side into Two so it can feed a 50 Amp camper or motor home can only supply the whole coach with 30 Amps. This can cause melting of plugs or wiring, damage motors or trip breakers of the load is not kept below 30 Amps. If you plug a 50 amp camper into a 30 amp only pedestal, you better not plan to run that second air conditioner. Most draw 12 Amps.
    (12 x 2 = 24) This only leaves 6 to power the 12 Volt converter. The minute you use the microwave or the electric water heater turns on. Pop goes the breaker

  6. Seems to be a lot of misinformation flying around here !
    Each leg of a 50 amp service will allow 50 amps at 120 volts, 120 volts between either hot and the neutral or 240 volts between the 2 hots, all this is controlled by the 2 pole 50 amp breaker in the power pedestal.
    50 amp services offer a great deal more capacity because there are so many appliances and toys in rv’s today, but still the most common rv’s service by far is the 120 volt, 30 amp system .
    50 amp services can be connected to 30 amp system simply by using the proper adapter that combines the 2 hot legs into 1, but this greatly reduces the amount of appliances that can be used at any one time.

  7. The misinformation is the reason that this site – RV’er should stop asking this. Let the manufacture of the rig tell you what and when to use it.

  8. Some of you guys are dangerous. 50 Amp service adapter to 30 Amp TT only uses one leg of 220 volt cord. 30 amp service adapter to 50 Amp TT ties ONE 30 Amp 120 volt to both 120 volt TT Circuits.

    Some big diesel pusher utilize a true 220 volt service. Electric dryers and ranges.

  9. Oh how I loath and despise when critical electrical and safety issues are minimized to ‘better’ or just simply inadequate non-technical yadda.

    This suggests that owners of RVs designed and built for a specific capability are “better served” by higher-‘ampacity’ service connections. That is specifically NOT true.

    If the pedestal provides 50A capacity, it does have more robust wiring, but that may only mean a 20 or 30 amp ‘rig’ may suffer less voltage loss to the pedestal – NOT somehow ‘better’ otherwise.

    I have a “30A Airstream”. I have adapters for both exclusive 50A and 20A pedestals – but I know that I will NOT be able to run my A/C by down-adapting to a 20A outlet – I might only get to run the charger and the microwave. I know I should be able to run all of my “30 amp” services in the rig from an adapted 50A service.

    I cannot draw 50A within my 30A RV system because I plugged into a 50A socket – the main breaker in the rig will prevent >30A over-loading.

    None of this accounts for what most won’t be able to determine – the underlying quality of the wiring to the pedestal, how many times one of the pedestal breakers had been tripped previously potentially weakening them to trip at lower load levels.

    If the camp facility has old or bad service, abused sockets or breakers – there is little most will know or be able to do about it.

  10. The correct designation is 50A, 120/240V, single phase.
    You have 120V available from leg 1 to neutral and 120V from leg 2 to neutral and 240V from leg 1 to leg 2. The neutral and the ground should be bonded together at the source (distribution fenter or panelboard). The 50A capacity is the capacity of the feeder. If you have a 50A, 2 pole main circuit breaker in your RV panelboard or at the distribution center feeding the power pedestal you are ugged into, and you exceed a 50A draw on EITHER leg or both legs simultaneously, you will trip the overcurrent protective device.
    It is wise to not load a main overcurrent protective device in ex ess of 80% nameplate rating. That means for a sttaight resistive load (no inductive loads, e.g., motors) you shouldn’t exceed a total load of 80% x 240V x 50A = 9600VA (9600 watts at 1.0 PF). The game changes if you have inductive loads (e.g., motors) and then you need to worry about inrush current LRA (locked rotor amperage) and overcurrent time delay protection vs. straight overcurrent trip protection.

  11. I have 30A service in my RV and I am adding a second AC unit. My dealer said they change the 30A cable to a 50A. One leg hooks to existing curcuit like original and the other leg gets it own curcuit breaker and the new AC is wired to it. Does this work? Sounds solid and safe to me.

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