Originally Posted by Zephod_beeblebrox2
That all has me thinking...
If I use two 15a sockets then I can use regular 15A cable. One cable for a 15A supply and two cables plus a 30A plug to two 15A connectors Y adaptor.
If you run two 15-amp shorelines to a home made Y-adapter plugged into the 30-amp socket at a campground pedestal, then the 30-amp breaker for the pedestal would not protect the cables from overloading with more than 15 amps on one side.
If each of the two shorelines had its own 15-amp overcurrent protection powering separate circuits on the bus end, then using the Y-adapter would be no more dangerous than plugging a #16 lamp cord into a 20-amp outlet at home.
But the photo of your breaker box submitted on the other thread shows your breakers fed from a single feed to both common bus bars. If you tie both of the split 15-amp shorelines to feed these bars, you have lost all protection for those cords.
What you need is #10 wire. Lowes has a #10 fifty-foot cord in safety yellow for $99.97 (#68598 ). They call it "20 amp" and put 15-amp connectors on it, but you would have to buy the 30-amp RV plug to make your pigtail anyway. This is only $24 more than your two 15-amp cords.
But as CaptainInsaneo has said, you can get the cords with the 30-amp plug molded on already for less at Camping World. The 25-foot length in his link (#78919) is on sale for $36.98, and the 50-foot length (#69601) is on sale for $74.97, three cents less than your wire cost alone without the connectors. It would actually cost you more to do it wrong.