Just asking for clarity but with the multi tap ballast trick I disconnect everything from the secondary, connect the common from the wall to the common on the ballast and use it as the common for the output. Connect 120v mains to the 120v tap and use the 277v tap as an output. But do I, need to connect the common to the ballast in this setup? I'd assume so.
Here is a drawing I just made on how to do it:
Hope this helps!
