RV Electrical; Home Receptacle Quandry

We are building a new home and the home builder refuses to put in a 30-amp connection; they will only put in a 20-amp or a 50-amp. I am having the 50-amp plug installed in my garage. On your website you mention the 50-amps at the park pedestal are two, 110-volt lines, (not 220-volts). I am not sure if my plug for my new home is 110 or 220-volts. Would I be able to still use the 50-amp plug, (I will need a 50-30 amp adapter), on my motorhome? I have a 35-foot Challenger motorhome. It has a 30-amp plug attached to the unit. Steve R. (no city/state)

Steve, I’m not sure why your contractor can’t install a dedicated 30-amp RV receptacle, (NEMA TT-30R), for your coach. Perhaps he's not aware of the RV 30-amp configuration? It's only used in the RV industry. A 50-amp motorhome will have two legs of 120-volts AC each; the coach circuits will be split between these two hot poles. Nothing in the RV (typically), is powered by 240-volts AC. The service is simply two separate circuits of 50-amps each, along with a shared neutral conductor and a ground wire. But if you take a voltage reading between the two hot poles, it will measure 240-volts AC.

If your guy can’t install a simple three-wire, 30-amp circuit, I’d be hesitant to have him install a four-wire, 50-amp circuit! It’s probably best to contact a local, licensed electrician who also understands recreation vehicles. 

Personally, I’d opt for a dedicated, 50-amp receptacle, (NEMA 14-50R), and like you suggested, use an adapter for your current motorhome. Better to be equipped for the higher current/larger conductors in case you were to ever upgrade your RV to one with 50-amp service. If you install only a 30-amp receptacle and then buy a new coach with 50-amp circuits, when you adapt the other way (30-50), through the adapter, you'll lose all the circuits on one of the hot legs inside the coach. Better to have the higher amperage receptacle and be set.