30 AMP to 50 AMP Adaptor

[Foldbak]

We camp at Coloma Resort on the American river often. Not all the river front sites have 50 amps. Half of them have two 30 amp outlets on their own breakers. Has anyone used on of these?

[BB_TX]

I haven't, but being both are 30 amp connectors there should be no problem. It is the ones with one 15/20 amp being the problem as the 15/20 is typically a GFCI outlet that will trip.

But one caveat. If both 30 amp outlets are on the same hot phase, it is possible that if both 30 legs are used near their maximum current that you could exceed the 50 amp rating of the neutral wire. You would probably not normally be pulling a total of over 50 amps combined from the two, but it is possible. If the two 30 amp outlets are on different phases, then there is no concern as the neutral could never exceed 30 amps.

The two hot legs on the same phase are additive on the neutral wire. Meaning the neutral carries the total current of both hot legs. On standard 50 amp split phase, the neutral current is reduced by the difference between the two hot legs and never exceeds the 50 amp rating of each leg.

[RMcNeal]

I use one quite often at SC parks we frequent. All of their sites tend to have 2-30amp breakers but no 50amp. I haven't noticed any issues running everything off AC. I even run the water heater off AC and not propane without any problems.
I also do not have washer and dryer yet, so that may make a difference. The air conditioners are typically our largest draw and both of them will run on 30amp with little else running.

[Daryles]

I would wonder how they have two 30A receptacles wired.
Are they BOTH on the same circuit?
Are they wired separately one on L1 hot and the other on L2 hot?
Pay attention to what BB-Tx said in his 2nd paragraph. Having L1 and L2 on a 50A receptacle the opposite phase cancels out on the neutral wire so it doesn't carry too much current.
Picture is how 50A pedistal is wired.

[Foldbak]

One has to assume that if they have two 30 amp and one 20 amp outlets each with their own breakers that it would be wired to handle 80 amps?

[BB_TX]

Originally Posted by Foldbak

One has to assume that if they have two 30 amp and one 20 amp outlets each with their own breakers that it would be wired to handle 80 amps?

Yeah, I agree they should. But even if they are wired to handle 80 amps, the potential issue is with your trailer wiring and power cord. That wire is sized for 50 amps. And even though there are two hot legs of 50 amps each there is only one neutral wire. But due to the nature of how split phase 50 amps works, the neutral wire will never carry more than 50 amps. And normally much less. Split phase means the two hots always have neutral current flowing in opposite directions. So self canceling on the single neutral wire. If, for example, hot 1 was carrying 40 amps and hot 2 was carrying 30 amps, the neutral wire would only be carrying 10 amps. The 10 amps being the difference between the two. Pretty easy to see how that works with an electrical schematic but a little harder to clearly put it into words.

If the two 30 amp outlets were on the same phase, then both hots would always have neutral current flowing in the same direction and the neutral current would be the total of the two. For example, if both hots were carrying 25 amps the neutral would be carrying 50 amps. So with 30 amp outlets it would be possible to exceed the 50 amp wire sizing.

[Foldbak]

Originally Posted by BB_TX

Yeah, I agree they should. But even if they are wired to handle 80 amps, the potential issue is with your trailer wiring and power cord. That wire is sized for 50 amps. And even though there are two hot legs of 50 amps each there is only one neutral wire. But due to the nature of how split phase 50 amps works, the neutral wire will never carry more than 50 amps. And normally much less. Split phase means the two hots always have neutral current flowing in opposite directions. So self canceling on the single neutral wire. If, for example, hot 1 was carrying 40 amps and hot 2 was carrying 30 amps, the neutral wire would only be carrying 10 amps. The 10 amps being the difference between the two. Pretty easy to see how that works with an electrical schematic but a little harder to clearly put it into words.

If the two 30 amp outlets were on the same phase, then both hots would always have neutral current flowing in the same direction and the neutral current would be the total of the two. For example, if both hots were carrying 25 amps the neutral would be carrying 50 amps. So with 30 amp outlets it would be possible to exceed the 50 amp wire sizing.

Thanks Bill. I think I understand what you're saying. So as long as I don't pish it I should be ok? Meaning if I'm running both AC's and a TV. Don't turn on the microwave?

[mhs4771]

Using that type of adapter you're limited to only 30 amps per leg vs a true 50 outlet that gives you 50 amps per leg.
So if Keystone screwed up (Heaven forbid) and put both ACs on the same leg you would stand a good chance of tripping one of those 30 amp breakers if running both ACs.

[BB_TX]

If your circuit breakers are clearly marked as to what they power you can make a reasonable estimate of what each leg will be carrying with those items on. Then you can determine what you can run and stay below 25 amps on each leg.

Some day I am going to sit down and draw some schematics of the 120/240 VAC power system and turn them into pictures I can post to help explain what I am trying to put in words.

[Foldbak]

Originally Posted by BB_TX

If your circuit breakers are clearly marked as to what they power you can make a reasonable estimate of what each leg will be carrying with those items on. Then you can determine what you can run and stay below 25 amps on each leg.

Some day I am going to sit down and draw some schematics of the 120/240 VAC power system and turn them into pictures I can post to help explain what I am trying to put in words.

Thanks Bill. I got a clear picture in a foggy head

[Lee-CI]

Only one sip of coffee before reading this thread and pretty sure y'all broke my head this morning! I followed it okay, but should have saved this one to read later on in the day

[BB_TX]

[rames14]

I felt a disturbance in the Force.

[bshgto]

Originally Posted by Foldbak

Thanks Bill. I think I understand what you're saying. So as long as I don't pish it I should be ok? Meaning if I'm running both AC's and a TV. Don't turn on the microwave?

Way to much thought in monitoring the use of power and potential for mistakes before your first cup of coffee, "wait can I turn on the coffee maker"? "Is that the wife using her hair drier"? Let me check and see if both a/c`s are on. Just go to Home Depot and buy an inexpensive voltage tester capable of testing for 220 volts. Then when you get to the campground test the 2 30 amp plugs for split phase circuitry it will tell you what you have to work with. $19 on Ebay, Home Depot

[Razahoryin]

Note.
If the second outlet is only a 15 amp GCFI
The gcfi will trip and is not compatible with the adapter

[c2itcliff]

Yes. Works like a charm. Even carry a 30' 30 amp extension cord to reach the neighboring site (if not occupied).

[Jake101]

We run a Hughs Watchdog in our power lines that would tell you what is going on with that setup. if there is a problem, it will tell you.

[c2itcliff]

Yup...have that too��

[GreG L.]

I use that adapter from time to time, I have one that has a 20A and 30A, used it a few times also. One of the times I used the 30/30Y I plunged in one 30A and made a list of everything that worked then swapped them out and made a second list, nice to know what's on each leg.

[scottz]

Originally Posted by BB_TX

Yeah, I agree they should. But even if they are wired to handle 80 amps, the potential issue is with your trailer wiring and power cord. That wire is sized for 50 amps. And even though there are two hot legs of 50 amps each there is only one neutral wire. But due to the nature of how split phase 50 amps works, the neutral wire will never carry more than 50 amps. And normally much less. Split phase means the two hots always have neutral current flowing in opposite directions. So self canceling on the single neutral wire. If, for example, hot 1 was carrying 40 amps and hot 2 was carrying 30 amps, the neutral wire would only be carrying 10 amps. The 10 amps being the difference between the two. Pretty easy to see how that works with an electrical schematic but a little harder to clearly put it into words.

If the two 30 amp outlets were on the same phase, then both hots would always have neutral current flowing in the same direction and the neutral current would be the total of the two. For example, if both hots were carrying 25 amps the neutral would be carrying 50 amps. So with 30 amp outlets it would be possible to exceed the 50 amp wire sizing.

It's nice to have experts to think about this stuff. Showing an oscilloscope on the two legs, in-phase then out-of-phase, might make it clear.