@Dennis Rosenthal Agreed with all who've said so previously, if there's no interconnection at all between the two different transformers, then phasing them is not really necessary. But, if you do want to share connections between them, correctly phasing to each other will help avoid unintended higher voltages and currents.
Here's a link to an excellent How To Guide from @MartyE about phasing.
http://www.martye.com/TipsandTricks/TipsandTrick2.htm
@Richie C. and @Craftech John's first posts above should also be considered regarding the differences between the KW and LW and which terminals are Common/outside rail.