50 amp down to 30 amp plug -- still 50 amp?

[ECones]

From the stupid questions department .....

A fellow told us last weekend that when we plug our 30 amp plug into a 50 amp plug through a 50 amp to 30 amp adapter we still get 50 amps. That doesn't seem reasonable somehow, but is that true?

thx ....

[babun]

Old-Biscuit wrote:

wnjj wrote:


True except the 50A has 2 phases to choose from and one may well be lighter loaded than the other. If you want the perfect setup, you'd have 2 dogbones to choose from with each one using a different 50A leg. 😛

Wish I saw that one before I bought my single dog leg!!
😞

[Old-Biscuit]

wnjj wrote:


True except the 50A has 2 phases to choose from and one may well be lighter loaded than the other. If you want the perfect setup, you'd have 2 dogbones to choose from with each one using a different 50A leg. 😛

[babun]

wnjj wrote:

DrewE wrote:

mkirsch wrote:
IMHO if you can plug into a 50A circuit, do it unless you know the campground has decent wiring. Often times campgrounds have less than adequate wiring and the heavier circuit will give you better power with less voltage drop.

If they're in the same pedestal, the wiring supplying both the 30A socket and (one leg of) the 50A socket is the same (with the exception of the few inches of wire between the breaker and the socket itself). The 30A socket itself may well be in poorer condition and make poorer contact than the 50A one, which is a different story and a reason in that case to prefer the 50A socket. At identical loads, however, the voltage drop from the campground wiring will be the same for either receptacle.

Put another way, a campground isn't going to have a separate distribution grid for the 30A socket and the 50A socket at the same campsite. If the voltage is low on one, it will also be low on the other.

True except the 50A has 2 phases to choose from and one may well be lighter loaded than the other. If you want the perfect setup, you'd have 2 dogbones to choose from with each one using a different 50A leg. 😛

I'm a retired electrical contractor new to RV'ing.
you have a great idea!!

Other than carrying my ohm meter into the store, is there a way to tell which 30/50 dogleg is wired to which phase {side of the 50 plug}
Do any manufacturers used a std layout, such as always one side all the time?

[wnjj]

DrewE wrote:

mkirsch wrote:
IMHO if you can plug into a 50A circuit, do it unless you know the campground has decent wiring. Often times campgrounds have less than adequate wiring and the heavier circuit will give you better power with less voltage drop.

If they're in the same pedestal, the wiring supplying both the 30A socket and (one leg of) the 50A socket is the same (with the exception of the few inches of wire between the breaker and the socket itself). The 30A socket itself may well be in poorer condition and make poorer contact than the 50A one, which is a different story and a reason in that case to prefer the 50A socket. At identical loads, however, the voltage drop from the campground wiring will be the same for either receptacle.

Put another way, a campground isn't going to have a separate distribution grid for the 30A socket and the 50A socket at the same campsite. If the voltage is low on one, it will also be low on the other.

True except the 50A has 2 phases to choose from and one may well be lighter loaded than the other. If you want the perfect setup, you'd have 2 dogbones to choose from with each one using a different 50A leg. 😛

[DrewE]

mkirsch wrote:
IMHO if you can plug into a 50A circuit, do it unless you know the campground has decent wiring. Often times campgrounds have less than adequate wiring and the heavier circuit will give you better power with less voltage drop.

If they're in the same pedestal, the wiring supplying both the 30A socket and (one leg of) the 50A socket is the same (with the exception of the few inches of wire between the breaker and the socket itself). The 30A socket itself may well be in poorer condition and make poorer contact than the 50A one, which is a different story and a reason in that case to prefer the 50A socket. At identical loads, however, the voltage drop from the campground wiring will be the same for either receptacle.

Put another way, a campground isn't going to have a separate distribution grid for the 30A socket and the 50A socket at the same campsite. If the voltage is low on one, it will also be low on the other.

[mkirsch]

When you attach to a 50A plug, that does not mean that suddenly 50A is being forced through your RV. Only the electricity that is demanded by appliances in your RV is going through your RV. For example, 10A for your air conditioner, 2A for your converter, another 1A to run the TV... 13A total, not 30A or 50A.

IMHO if you can plug into a 50A circuit, do it unless you know the campground has decent wiring. Often times campgrounds have less than adequate wiring and the heavier circuit will give you better power with less voltage drop.

[ECones]

As I understand it, it could also keep him from having to go outside in the rain to reset the 30 amp breaker on the pole if he manages to overload it. It would trip inside.

Maybe that's his goal.

[wnjj]

ECones wrote:
The fellow we talked to said he always plugs his 30 amp trailer into the 50 amp plug through an adapter so he'd have 50 amps available, and being that I'm no electrician I didn't argue. But I did understand that we're really only using half that plug (Roy's post above) so I seriously doubted it.

Luckily, I knew who to ask. 😉

Thanks for all the kind responses and, once again, nobody pointed out my mental deficiencies. 😉

Technically he does have 50A available at the other end of his cord. Using only half of the 50A service just means there is only 50A and not 100A available. As some others have stated, the current coming from the pedestal depends upon what is limiting it. With a 30A pedestal receptacle, the 30A breaker on the pedestal will limit you to 30A.

If you now use a dogbone to connect to the 50A receptacle, there is indeed 50A available. If the trailer does not have a 30A "main" breaker there is nothing stopping it from pulling up to 50A. The setup in the picture a couple of posts above without a main breaker could use (15+20) = 35A if plugged into a 50A dogbone.


This situation is no different than a light-duty extension cord plugged into a 20A receptacle at home. If you then plugged an electric heater into the extension cord, you could overload the cord without tripping the 20A breaker. In this case, just like the RV dogbone into 50A you can't just rely on the receptacle supply's breaker to limit the current if the device plugged into it isn't capable of the load.

Many RV's with 30A cords have 30A main breakers to prevent this.

The reality is his trailer is limited by the lower of his main or the pedestal breaker. By using the 50A service, his effectively now only limited only by his 30A main. This may result in slightly more power available for him if the pedestal 30A breaker would have tripped at something less than 30A.

[ECones]

The fellow we talked to said he always plugs his 30 amp trailer into the 50 amp plug through an adapter so he'd have 50 amps available, and being that I'm no electrician I didn't argue. But I did understand that we're really only using half that plug (Roy's post above) so I seriously doubted it.

Luckily, I knew who to ask. 😉

Thanks for all the kind responses and, once again, nobody pointed out my mental deficiencies. 😉

[wa8yxm]

Well. this may sound strange but...

YES: you can still GET 50 amps.. BUT.. You can only accept 30 of 'em.
(SO what happens to the other 20? They are simply left in the box as it were)

IF you try to draw more than 30 amps you still get the CLICK OF DARKNESS (Sound of a circuit breaker tripping) only it is INSIDE the RV, not out where you need to put your shoes on to reset it.

Some folks worry about the posibility of a short that draws say 45 amps and overheats the shore cord.. Possible in a lab,, Basically impossibly in real life.. So do not worry about it (You might do it if you use an extension cord adn the plug/outlet junction is in a puddle but only the extension cord would be at risk not your RV's cord)

[red31]

Main breaker? ya mean at the pedestal? :E

[RJsfishin]

Nothing to do w/ the question, but don't even try to figure out this 30/50 amp service stuff, because it is stupidly wrote wrong !

W/ a 30 amp service, you have a "total" of 30 amps available to your RV
A 50 amp service would lead a person to believe that you have 20 more "total" amps available to your RV, when in reality that is not true at all.
It is really 100 total amps available.

But no different than the guy that wrote the dictionary, he was an idiot too.

[MrWizard]

the potential for 50amps is there
it will take more than 50 amps to trip the breaker at the pedestal
BUT your RV 30 amp breaker means you can never use more than 30 amps
what has not been mentioned
is there will be less voltage drop, so when drawing 20+ amps the voltage will still be higher than what it would have been if you were plugged into the 30amp pedestal outlet, even at 30 amps the voltage should still be 115~120v to the RV

[Golden_HVAC]

If you have a 30 amp RV, it will have a 30 amp main breaker, limiting you to just 30 amps into the RV.

If I am using my voltage booster, it will use about 2 more amps than the RV consumes, and I will try to use a 50 to 30 amp adapter while using the booster. I would still be limited to just 30 amps into my RV power panel. ..

Good luck,

Fred.