Upgrading 30 amp to 50 amp for RV service

I was wanting to know it it would be safe to replace a 30 amp double pole breaker with a 50 amp double pole breaker. The 30 amp currently feed a well pump and a barn. The barn and the pump piggy back off the 30 amp breaker. I want to abandon the barn feed and run 300 ft of 6/3 to my RV service panel and piggy back the pump off of that 50 amp double pole breaker. Can I do this?

• I made some edits which I hope make the question more clear. If not, please roll back – mmathis Jul 17 '17 at 17:10
• You can't piggyback like that without a proper subpanel. Plus that long run will kill you on voltage drop. Since you'll be adding the 6/3 anyway, why not continue the barn run in service, and add the 6/3 as second circuit? Make sure it goes to a different place, can't parallel two circuits of the same voltage outdoors. Separately, there's a way to carry all the power you want on the cable you already have, that is probably cheaper than trenching a pull of 6/3... but it requires wizard tier intelligence. – Harper Jul 17 '17 at 18:44
• Can you post the nameplate of the motor load? Also, how much load is the RV, and what is the make and model of this "RV service panel" you have? – ThreePhaseEel Jul 17 '17 at 22:06

What @Harper said. The problem we have have with a question like yours is that we could say "yes you could update it" but we really don't know is what kind of loads you are applying at the end of a circuit. We are guessing that it is greater than 30A because you want to upgrade. Also you give us a distance of 300' which is a substantial distance so voltage drop will surely come into play.

For example if your load is 40A at 240V which would be 9.2KVA then at a 3% Voltage Drop. Then you could run 333' with a #4. A #6 would only be good for 210'. If you load were 45A or 10.35KVA the distance with a #6 would be no longer than 186', A #4 would get you 296' so technically you would need a #3. Buy the way this is all in copper.

So you need to get distances and loads for the pump either in HP or KVA and voltage requirements and a demand load for the rv either in Amps or KVA and operating voltage. Then there could be a more complete and informed answer.