On 4/9/2011 10:29 AM, The Daring Dufas wrote:
On 4/9/2011 8:30 AM, Tony Miklos wrote:
On 4/9/2011 12:38 AM, David Nebenzahl wrote:
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?
Look at the picture. The primary side has been overheated, the secondary
side looks fine. Looks like an over voltage problem to me.
I wonder if our intrepid OP has done the basics involved in troubleshooting
instead of flitting around from place to place?
In the case of a power problem, you always start at the source by
measuring voltage and current. It could be a very simple problem
like a bit of insulation skinned off a thermostat wire that only
shorts out when everything is buttoned up and vibration from the
running unit causes the short circuit. If you ever watched the TV
program MASH, you would see the surgeons run the intestines looking
for a nick in the wall of the organ. Wiring is the same way sometimes.
I'll inspect the wiring and often find a small cut or tiny area where
insulation is missing and sometimes the wire is bent over a sharp edge
of the cabinet where it's fine until you close things up. I wonder if
the supply voltage to the transformer is what it's supposed to be? Most
domestic household air handler/furnaces are powered by 120vac but some
may require 240vac if there are electric heat strips. I would check the
voltage feeding the transformer first.
TDD
Yes, I've done all those things. The supply voltage is fine. I've inspected
the wiring at great length and can find no evidence of problems; it all looks
pristine. It's a gas furnace, and there are no 220 circuits running anywhere
near that area of the house.
Thanks.