How does a Dogbone electrical adapter allow you to plug a 50 Amp RV into both a 20 Amp and 30 Amp outlet, and what implications does this have for the internal wiring?
Asked by Neel Vernekar 
4 months ago
Last Updated: May 10, 2024
Hey, check out this cool Dogbone electrical adapter for RVs! It lets you plug into both 20 Amp and 30 Amp outlets, which is perfect for your 50 Amp RV. Have you ever wondered how the wiring inside works with this adapter?
If the park pedestal complies with current code standards, the FCI on the 20A plug will trip.
Yeah, I can see where you’re coming from on that
Is neutral.
The absence of a FI is because it’s seen as a “sub” panel…
All 20 amp outdoor outlets need to have FCI protection, according to .
There’s nothing wrong with those things; if you’re complaining about them, the issue might be with you. There’s also a 30 amp option connected to a 50 amp plug in the single-phase 110 volt setup. Many RVs require adapters because not all RV parks have standard 50 amp or 30 amp plugs or even 110 volt receptacles. Before these were sold in stores, I had to make my own.
You could potentially draw 40 amps for a while before the 20 amp breaker trips; then the 30 amp breaker will follow suit. The load on each receptacle is likely evenly distributed. It’s probably not up to code, but this setup allows you to pull 40 amps through a 30 amp RV cord.
No it permits 30 on 1 line and 20 on the other using a 50 amp cord
Absolutely 👍
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So?
With one leg of the 50 amp plug receiving 30 amps and the other receiving 20 amps, it seems like the only way it would work. Otherwise, how can you be certain that the 20 amp and 30 amp outlets are on the same phase? It wouldn’t add up to 50 amps in that case. You’d essentially have a 50 amp panel in the RV with one leg at 30 amps and the other at 20 amps. It should function properly as long as you don’t run everything simultaneously.
Have you not seen the RV guy on YouTube claiming that the 50 amp receptacle actually produces 100 amps? 🤣🤣
Oh no I haven’t. Lol.
That was my initial thought too – what if the 30 and the 20 were on the same phase
Yeah, it seems like there must be more to it than just everything being connected. Perhaps fuses, regulators, or converters are involved. Connecting all legs with a tail would simply result in back feeding each other. If this setup is actually capable of delivering 50 amps, there has to be something additional at play
I have, and let me tell you, he is quite the character.
Someone should definitely purchase one and cut it open lol Or maybe just ohm it out
An RV 50 amp actually consists of two poles of 50 amps EACH, giving you a total of 100 amps because RVs only utilize single pole circuits. On the other hand, the next RV supply is a 30 amp single pole, which means only one 30 amp circuit compared to two 50 amp circuits. It can be quite confusing for those unfamiliar with RV electrical systems! 👍
I’m pretty sure I have, that’s how I know…
Sure thing! Just let me know if you need any changes made.
Just to let you know, was right when he said you can connect 100A of 120V loads.
Gives you 20A on one leg and 30A on the other.
I was under the impression that it was a 3 prong plug, but if it turns out to be a 4 prong 120/240 plug, then it all makes sense now. The RV owner needs to be aware that anything running on a 2 pole breaker will trip after 18 amps. Hopefully, they have the 20 and 30 amp breakers tied together so if one trips, they both do.
Do you know why thinks it might trip at 18A?
Has found that a breaker is only rated for 80% of its face value, and the thermal sensors in the breaker cause it to trip when it hits a certain temperature and the amp draw raises the temperature. Although breakers are designed to trip at 80%, they can sometimes handle higher loads before tripping as long as the thermal sensor indicates that it is not hot enough. The longer the amps are being used, the hotter the breaker will get, so it may take a while for it to trip. Ultimately, it all depends on the thermal sensor in that specific breaker, and they are not consistent across all breakers.
You’re mistaken 🤦🏻🤷🏽♂️
Here is a circuit breaker trip curve indicating that it can handle 100-125% of its rating.
Was hopping from one side of the 50-amp receptacle to the other and saying it could deliver 100 amps. He also insisted that there was no current if both L1 and L2 were utilized due to a “phase shift,” but somehow everything still worked.
Seriously, the breaker needs to be 100 percent rated. I just showed you the code. If it’s only rated for 80 percent and runs for more than 3 hours, you can’t do it according to code. I’m not sure what else to say.
Can you point out in the code where it mentions a breaker being rated for or tripping at 80%?
If there are any components inside that plug, it could cause a breaker to trip as they attempt to feed power back and forth.
Explains that only the neutral and ground are shared, while the hots are split. This setup prevents back feed or breaker trips.
They must intersect at some point. It’s absolutely necessary. Unless there is an internal splitter inside that adapter
The hots do not intersect; the 50 amp cord from the RV plugs into the adaptor, just like it would plug into a 50 amp receptacle if one were present. One hot feed comes through the adaptor from the 30 amp, while the other hot feed comes from the 20 amp. The two hot feeds never link to each other.
Then how does it receive the 50 amps? It should either be 30 or 20, not both. I understand that the 50 amp plugs in normally, but it still needs to draw power from somewhere.
One leg is from the 30 amp, while the other is from the 20 amp. It’s not a true 50 amps as you pointed out, but everything in the rig functions fine as long as they don’t activate too many loads simultaneously…
On one leg, you have 30 amps. On the other leg, you have 20 amps that lead to a 50 amp receptacle. You cannot reduce from 2 legs to one connection without them intersecting and linking somewhere.
The 50 amp plug consists of 3 poles and 4 wires – 2 hots, a neutral, and a ground. The hots are never interconnected, but the neutrals and grounds are connected in the adaptor…
Here’s the RV recept…
They’re likely 30A 120V and 20A 120V, while the 50A is 120/240V. That would make sense.
If that’s the case, you won’t actually get a true 50A, at least not like you would with the standard 50A RV outlet. This would provide you with 50A per leg, at 120/240V.
The way I understand it with this setup, you’re supplying your RV panel with one leg of 30A 120V and the other with 20A 120V. It’s convenient but still below what the 50A RV outlet can offer.
How did you conclude that the two hots touch?
Well when they come together, they touch.
Where exactly are you saying they intersect?
Alright, I understand where I went wrong. I mistakenly thought it was a three-prong 50 amp plug, but if it’s four prong then I see the possibility. So, one leg would be 30 amps to the RV and the other 20. ot it 🤦 but even with a 30 amp 240 volt AC in the RV, one leg will still trip after reaching 80% of the 20 amps
Perhaps it’s more common in this area
Fun fact: breakers actually don’t trip at 80% capacity 🤦🏻
It’s not guaranteed, but they are typically only rated for 80%. For example, if an appliance has a rating of 19 amps, you would need to upsize it (along with the wire size) to a 30 or 25. A 20 amp circuit wouldn’t be sufficient according to code.
I think 25 should do the trick.
In most RV parks, the ground receptacle and the 30 amp receptacle are on separate phases. Because of this, they usually utilize the two hot wires, resulting in a 30 amp leg and a 20 amp leg on the RV plug.
Hey, that’s not quite accurate. You should check out a breaker trip curve to see they can actually hold 100% or more of their rating.
I remember reading about that in 210.20(a). It seems like the specific breaker rating plays a big role. Some are only rated for 80%, while others can handle 100%. RV owners might not be aware of this, but if they run an air conditioner all night for more than 3 hours, it’s considered a continuous load. So, even if the breakers are rated for 80%, they could still trip around 16 amps
Nope, that’s not quite accurate. What I meant was that circuits must be sized for continuous loads at 125%. For non-continuous loads, you can go up to 100% of the breaker’s capacity.
If the breaker is rated for 100% at continuous load, then you don’t have to size the circuit at 125% for continuous loads
Well, not all of them are. In my case, I have a 50 amp trailer with one hot and one neutral wire
Why would someone even think the hot wires would connect in that area? If you honestly believe that, maybe steer clear of electrical work in the future
As long as the phases are in the right order, it should work out fine
Typically, they run the hot feeder from one side of the 50 amp plug to the 30 amp, and the other side to the 20 amp. That way, the adapter can access both hot sides
In my experience, all the RVs I’ve dealt with that have 50 amp service were connected to 240v, even though the campers themselves don’t need 240v. If both feeds are on the same leg of single phase, it might be a bit worrisome for the cord neutral
Looks like you’re the weakest link 😂
That’s silly.
Let’s take a look at the plug setup and the device you’re connecting directly before jumping to conclusions. Can you provide more details?
Honestly, I wouldn’t spend any money on that device. It seems like a waste to me.
What would you do if your camper needed a 50A receptacle but the campground only had a 30A or a 20A available?
I totally get what you mean. I’ve been to a few camps that had only 30 amps and then a FIC 20. Just curious how they were set up.
I mean, you won’t be able to achieve 50 amps, but it might function. Not something I’d risk doing.
No content
In RVs, 50 amp outlets are rated for 240 volts, 30 amp outlets are rated for 125 volts, and 20 amp outlets are rated for 120 volts. I would need to see the plug ends and panel plugs to have a better idea of the situation. Something seems off here.
Nothing suspicious at all. The 30A powers one leg and the 20A powers the other leg.
If you use more than 20 amps at 240 volts, you’ll trip the 20 amp 120 volt breaker. Unless both outlets are on the same side, you’ll only get 20 amps at 120 volts.
It’s pretty uncommon to find any 240V loads in a camper, dude.
If the 20 amp breaker is a FCI, as it should be by code, it will trip the FCI. In that case, it’s probably not worth spending money on.
A 50 amp RV plug is designed for 50 amps at 240 volts, while the 20 amp and 30 amp plugs are for 120 volts. The system provides a 20 amp and a 30 amp option, possibly with 240V/120V capabilities, but be cautious as it could overload the neutral wire.
Just test the resistance!
It’s not difficult to understand
My camper van has a 240v 50 amp plug. But there are no appliances onboard that need 240v. What happens is that one side of the RV panel uses leg 1, while the other uses leg 2, and the neutral connects both. Interestingly, one of my AC units is connected to one leg, and the second AC is connected to the other. Many RV parks do not offer a 240v 50 amp service. Instead, they provide a 120v 30 amp service. So, the adapter that connects the RV plug to the receptacle combines leg 1 and leg 2 from the RV into a single hot from the park’s service pedestal. It works fine, but it’s essential to remember that only a 30 amp breaker is powering the RV. Running both AC units simultaneously will trip the breaker. Certain adapters, like the one depicted, provide a workaround for this limitation. They supply each leg on the RV from a separate breaker. This is where issues can arise if one is not attentive. One of my adapters features two 30 amp plugs. If the neighboring space is available, I could utilize both their pedestal and mine, powering each leg in my RV from the two breakers. This setup works well on the hot side since I am only using 30 amps on wiring designed for 50 amps. However, if the two outlets I am using share the same leg, my neutral may end up carrying up to 60 amps, exceeding the specifications. The adapter shown in the photo is designed to solve this by limiting one leg of the RV to 30 amps and the other to 20. This prevents overloading the neutral. Despite all this, the setup may not offer significant benefits, as you are still limited to using a single AC unit unless you are aware of which leg each appliance is on. Most RV owners may not be familiar with their circuit layout in such detail. Apologies for the lengthy and technical explanation, but I found it quite intriguing when we acquired our motorhome.
When you look at the switch box inside an RV, the main breaker is positioned at the center of the panel, with one leg feeding 120 volts to the port and the other to the starboard. This setup is pretty standard for RVs.
Make sure that RV connection is equipped for 220 volts
30 amps at 120 volts on phase A
20 amps at 120 volts on phase B
Obtaining 50 amps from this device is impossible; I honestly don’t understand why someone would create such a dangerous gadget.
These adapters only function if the 120 volt plug does not have FI protection. If it does, the FI will trip.
It’s astonishing how many uninformed individuals confidently share their incorrect beliefs here, demonstrating a total lack of knowledge in electrical theory.
It only functions properly if the hot wires are not in sync with each other