In my hometown (Oradell NJ) there's a few 50's era high end houses that are fed 3 phase power. Looks to be open deltas with a wild leg (240V center tapped grounded, and 208 to the wild leg). Yhese high end houses must have had central air built in as new, and back then the units must have required 3 phase power. Once went to a garage sale at one of these houses, and I saw a main panel, and what probably was a subpanel for the rest of the house (non air conditioning 120V loads). I suppose one could connect an electric dryer using the wild leg, if you're careful to make sure the 120V motor does in fact get the 120V line and the other end of the 240V heater element gets the wild leg. Probably not code, though...