Multiple post reply:
RE: "True of home, not RV dryers" yes, he was speaking of a home dryer outlet and so was I, I've done considerable work on one of the old dryers in my home. Replaced teh heat element more than once, assorted bearings and rollers, finally replaced the entire dryer.
Re: different phases, no, same phase. It is not multi phase, it is split phase. both legs are totaly in phase so if you label them
A(120v)B(120v)C and you measure A to B, it's 120 volt, Measure B to C it's 120 volt, Measure A to C it's 240 volt, but the phase is the same (as cited above) if you measure A to B and C to B however then yes, the phase is backwards.
but to add they must be in phase. Hence the label "Split phase" because a single phase is split between the two legs. The transformer is center tapped.
And finally re: hooking A & C up to a 30 amp outlet... Very bad idea (As that one person found out) the 30 amp outlet in my back yard is a proper 120V line
Interesting fact: The generator on my RV is 120 volt only, it can not power 240 volt gear w/o a transformer. Why they did this I do not know unless it has a single 120 Volt winding (it has 2 30 amp breakers)