On 4/8/2011 8:22 PM Steve Turner spake thus:

On 4/8/2011 7:58 PM, David Nebenzahl wrote:

On 4/8/2011 5:52 PM Steve Turner spake thus:

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.

How 'bout installing an in-line fuse next time you replace the
xfmr? I'd put it on the secondary side. That way, if there is an
overload, the fuse will blow instead.

Thinking maybe I should spring for a transformer with a manual reset, like this
one:

http://www.pexsupply.com/White-Rodge...unt-14937000-p

Would that protect me from having to replace the damn transformer every time?
It looks like the circuit breaker is on the 24V output side; I'm a little fuzzy
on how that would protect the input side of the transformer...?

Why in the world would you think you need to protect the primary side?

Unless you've got a *really* weird problem--namely, severe overvoltage
spikes--there's no way the damage is coming from that side. It's got to
be because of overcurrent on the secondary side.

Unless there's something really messed up with your house's wiring ...


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