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/bbqboye...7626457562742/

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?
Hi,
Is the x-former gets hot when in use? Unless it is under rated for the
application, it should npot blow so often. It is just 120-24V AC step
down tranny. Buy one of hevier one(bigger size and really heavier in
weight than stock) If it blows again, something on the load side is wrong.