Blew another damn transformer on my Trane XB80

[trader_4]

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6-07_04012009.pdf

ead of the stock 40W just in case it was underrated. I measured the operati ng output current during cool or heat and it maxes at .6 amps when 2.0 woul d be the limit. I cleaned up all the sloppy wiring from the installation an d so far no blown fuses but with such an intermittent problem you never fee l like you got it for sure. The only problem I could find was during heat c all the red light would blink for 3 times indicating a problem with the saf ety pressure switch (enough gas pressure?). I temporarily bypassed the swit ch then it would latch and the heat would work fine. The only thing I can f igure is that it the unit tries many times to turn on the heat and the pres sure switch never makes the board commits suicide and deliberately blows th e fuse so that you have to call a service man???? Sounds crazy but I wonder . I'll replace the pressure switch and see if the problem ever returns. For now I have a bunch of 2 amp (instead of 5A) fuses on hand to keep from blo wing the transformer again. From the many web posts this seems like a commo n problem.

blows the xformer.

alled a new xformer and added a PTC fuse device in series with the secondar y just in case. A regular fuse rated for an amp or so above the xformer ra ting is a good idea. Also tie wrapped all the loose wires so none were ru bbing on anything.

And other times, it's just that the supplier of the part is making crap and it just keeps failing. I had that experience with a Sears de-humidifier. The fan burned out, so I bought a replacement one. It lasted less than a year. Then foolishly I bought one more. That one burned out when it was first powered up. And yes, it was wired in right, it was just a simple AC two speed motor.

Finally I started googling and saw that so many other people were having exactly the same problem. But Sears just kept buying crap from whoever the supplier was. Posts complaining about it went back many years.

One choice might be to find a different Xformer supplier, even a slightly different one as long as it can be mounted and the specs are equal or better.

[TimR]

Wait a minute, you got several years out of a dehumidifier?

How the heck did you do that?

[Tekkie®]

TimR posted for all of us...

He turned it off and never turned it back on.

[Diesel]

It shouldn't have happened the instant the short occured. More likely, it damaged the insulation on the secondary/possibly the primary windings due to excessive heat build up from the short circuit condition.

The short won't blow the transformer right away...See above. You

*should* notice if the transformer was being shorted in such a scenario the unit as a whole wouldn't run properly due to some voltage loss caused by the bad wire(s). A transformer isn't a fuse and we're not talking about MV or HV transformers that can blow in a short period of time due to a short circuit condition. And the reason they go ahead and blow is because you're dealing with alot! more amps with alot more voltage present. So, the heat build up they experience during a short circuit is much much higher and occurs much faster.

It's a low voltage transformer, so, you shouldn't have experienced transformer failure the moment you shorted out the secondary. It had to have been an ongoing issue for sometime to cause enough internal damage to the transformer for it to have failed. And, as I wrote previously, it's due to insulation breakdown on the secondary and/or primary windings. Eventually leading up to popping the fuse (if the primary is severely damaged). But, by then, you've essentially already killed the transformer. So, the fuse is a final 'safety' to try and reduce the chances of an outright fire in the unit.

[trader_4]

Who said that it did? From what I see in this thread, people are having problems with them burning out, they put a new one in and it lasts for days or months, then it fails.

If it were me, I'd put an appropriate fuse temporarily on the low voltage side to find out if it's failing from overload or if it's just failing because it's Chinese crap.