30A breaker on 50A receptacle?

My recommendation is do exactly what you first suggested, then take black paint and write "30 amp only" on the box the outlet is in.

However, a better suggestion is to run heavy enough wire to carry the full 50 amps and install a 50 amp breaker. I am in favor of over-engineering for future growth. I don't know how long your run is so I can't judge if 6/3wG will do for 50 amp.

Here is a website that has a Wire Gauge Calculator that you can use to find just how heavy a wire you need for your specific run to use the full 50 amp rating. You put in voltage (you can use either 120v or 240v), use single phase, use 50 amps, use the length of wire you would have to run from the breaker box to the outlet box (one way only), use 3% loss and click calculate.

I have a 30 amp RV and put a 50/30/20 pedestal next to it. (Insurance in case I ever get a 50 amp unit). Someone suggested that I run heavy enough wire to use an 80 amp breaker at the house so I could use the 50 amp AND the 30 amp at the same time but that would have required 3g wire. I didn't want to go to wire THAT heavy, so I used 50 amp rated wire and 50 amp breakers.

dougrainer wrote:
Install the 30 amp breaker and install a 30 amp receptacle. Then use the 50 to 30 adapter. That way, Nobody else will ever think it is nothing more than a 30 amp receptacle. Leave the 50 to 30 connected to the receptacle and there will be no hassle when connecting your 50 amp cord. KISS is what is needed. Doug

It seems clear from the other thread about dogbones heating that 30 amp is not quite enough for my RV. But TWO 30 amp circuits on a '50amp' receptacle should be plenty. The circuits in the RV panel are pretty balanced.

I figure "why run the risk of overloading a dogbone?"

But what is the risk of "somebody" (it's only me) trying to draw too much out of my '50 amp' receptacle. Are you worried that the 30 amp breaker won't do its job?

I plan to put a label on the receptacle that says "30 amp max".

Install the 30 amp breaker and install a 30 amp receptacle. Then use the 50 to 30 adapter. That way, Nobody else will ever think it is nothing more than a 30 amp receptacle. Leave the 50 to 30 connected to the receptacle and there will be no hassle when connecting your 50 amp cord. KISS is what is needed. Doug

THe basic rule is the Circuit breaker should be no larger than whatever it protects (It protects the wires and outlet. what you plug in is not protected by the breaker)

SO if the wire is rated 50 amp, and the outlet is rated 50 amp, any circuit breaker smaller than 51 Amp is just fine (51 amp is too big).

IN fact.. I sometimes recommend that.. If you have a 30 amp RV and are having the thing installed professionally (The outlet) INstall a 50 amp Outlet, with 50 amp Wire (Six or heavier ga) and a pair of 30 amp breakers. then use a dogbone to 30.. That way upgrading to 50 amps (later if you choose) involves ONLY replacing the breakers, not new wire or outlets. Way cheaper

ALso,,,, on my 50 amp RV the Generatgor breakers are 30 amp so you should have FULL POWER or darn near full on 30 amps if you are well balanced.

I believe you need a 40 amp breaker to meet code. Not a safety issue using a smaller breaker but a NEMA 14-50 implies there is at least 40 amps available.

Done it, have it. Our electrician ran a 10/3 w gr. out to our carport, on to a potential rv parking. We could have a 30 a 240 v pedestal there. 30 A double pole Breakers installed at both ends.

yes its fine and its legal
you ARE protecting the wire
its ok with code to use a smaller breaker, to be over protective

it is only against code to use a breaker too large for the wire {won't trip before wire melts and burns}

You can always use a breaker rated lower than the outlet it is servicing. Just not the other way around.

It is fine to use a 30A breaker on 50A service. It is not ok to use a 50 amp breaker on wire rated for 30 amps