With 117v in and terminals 21 & 5 connected I should see 293v ac across terminals 20 & 10. The current rating of one winding is .320A the other is .500A. By connecting these windings in series is the current rating .320A?
Yes, that must be right. 0.320A. The loading limit is often decided by when the winding resistance generates so much heat that it starts being a problem for the longer-term transformer reliability. The weakest link sets the limit.
