You guys are incorrect. If you connect two 12v transformer secondaries together via one end of each, and do not care about getting 24 volts, polarity does not matter.
As for the primaries, they could either share a single circuit or be fed from a multi-wire (120/240) circuit, and again, since there's no interest in 24v, phase doesn't matter.
In other words, you can use any standard transformers of adequate capacity.
[This message has been edited by Larry Fine (edited 09-14-2006).]
