As a student and always trying to learn I have a question for you guys.
I was working on a Trane furnace TUD080R, and upon arrival I found a bad XFMR with an open primary side. I inspected furnace and could not find any problems with the wiring so installed another transformer. Reset power called for A/C and the smoke came out of that transformer as well(I really hate when that happens, as I have never figured out how to get the smoke back in). So I started doing some digging and found out that the two wire feeding the condensing unit was shorted together. The weird part is that it never popped the 5amp fuse on the board, nor did it short out the secondary side. Can somebody please explain????