wrote:
On Tue, 17 Jun 2014 06:34:20 -0700 (PDT), wrote:

On Friday, April 8, 2011 5:52:06 PM UTC-7, Steve Turner wrote:
A continuation of the "Why does the 115V-24V transformer keep blowing on my Trane XB80?" discussion I started on 04/02/2011.Yep, My A/C unit blew another transformer. Pictures (and wiring diagram) he http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/Trane's manual for the unit is here (for perhaps better viewing of the wiring diagrams that I also copied to my above flickr site as jpg images):http://www.trane.com/webcache/un/fur...7_04012009.pdf As you can probably see in the pictures, there is visible charring of the 115V leads going into the transformer, and of course the 115V circuit is open (again). If you didn't see my first thread, this is the third transformer the unit has blown. In the previous discussion, it was discussed that perhaps the first one just blew because of old age (6 years), and the second blew because it wasn't a proper replacement (poor quality, made in China, etc.). This third unit is most certainly a proper

replacement, and it's most certainly indicative of a real problem I have somewhere else in the unit. I didn't see any such charring on the previous two units, at least not like this.I never got a real chance to test out the system after installing this third transformer. We had cool weather for several days, and I never tried to force the system to come on so I could monitor it; that was probably a mistake. Unfortunately, I was also absent from the premises during the extended times when the unit was most likely operational, so that didn't help either. However, my family tells me that it WAS working and cooling the house rather nicely, for at least a day, perhaps two. I'm getting 115V in all the right places, so it doesn't look like an over-voltage condition to me. Perhaps it's an overheating condition? It looks to me like the only real load on this circuit is the blower motor; could the motor be causing this? The blower spins freely when I turn it by hand. Start capacitor on the

motor maybe? Relay on the control board perhaps?

Hello, I am having the same exact problem and have replaced the transformer a third time with one of the correct rating as the manufacturer (70VA). The second time I replaced it with a 40VA because I assumed the one i replaced was the correct size. The Primary side keeps getting burned up. What causes that?
Use a 90va or better transformer and fuse the secondary. Buy a good
brand name transformer. Eiuther you are overloading the transformer or
the transformer is junk.

Hi,
There are a few listings at eBay for a brand name NOS x-formers at
around 90VA rating. Not Chinese El Cheapo ones. For ~25.00.