On 4/14/2011 12:06 PM, Smitty Two wrote:
In ,
Steve wrote:

On 4/14/2011 12:41 AM, Smitty Two wrote:
In ,
Steve wrote:

Just mentioned elsewhere that I have a new transformer on order and I
can't
really do anything until that arrives.

Sure you could. You could open up those other two transformers and check
for an open thermal fuse. As I recall, you said neither of them failed
in the same manner as the third. I still say you could have 3 distinct,
unrelated failures.

The design of the first transformer makes it virtually impossible to open it
up
(remove the tape) without destroying the windings, (which I did) so there is
no
possibility of "repairing" it by installing a thermal fuse (as some
suggested).
There is evidence of burning at the input contactors just like there is on
the third transformer (the one I took pictures of), but not quite as bad. I
wouldn't call it an "explosion". There is no evidence of a thermal fuse.

On the second transformer (a completely different brand and style) there was
no
evidence of burning. Again, it too was virtually impossible to open up with
destroying it, so I didn't bother. However, because everyone has been so
curious, I just did open it up (destroying it in the process) and there IS a
thermal fuse on the input side; it is open, which explains why there is no
burning.

The third transformer is similar to the first in design (except for the extra
208 and 240 legs, which, per the instructions, I taped off and ignored). It
is
also virtually impossible to remove the tape to gain access to the primary
windings without breaking through the wires, but I did, and again there is no
evidence of a thermal fuse.

I see no reason to conclude there are "3 distinct, unrelated failures".

Just because you can't fix something, it doesn't mean that failure
analysis is moot. I'd be doing serious exploratory surgery on all 3 of
those transformers to try to understand what the hell happened.

I'm not "concluding" that there are 3 distinct unrelated failures, I'm
suggesting it as a possibility.

The first, OEM transformer lasted 6 years. The second transformer lasted
a few days, and by your own admission was a cheap knockoff that may not
have been suited for your application at all.

Others sorta concluded that for me. It was "Made in China" and has a bit of a
different form factor, but that's the only evidence I have so say it might not
have been "suitable". The transformer was similarly rated, and internally it
doesn't look much different from the others, so I still have no real reason to
believe it shouldn't have worked.

And the 3rd transformer may well have failed due to improper wiring, or
a loose connection leading to excessive current leading to insulation
breakdown and a hard short, or as has been suggested repeatedly, a fault
somewhere on the secondary side.

You've also agreed that there are wire color discrepancies and several
respondents have opined that both halves of the primary should, perhaps,
have been wired in parallel to accommodate the current requirements.

I brought the old transformer to a local HVAC supply house, and the sales
person (whom I perceived to be at least somewhat of an expert), gave me the
third transformer as a suitable replacment. I chose to connect the transformer
according to the instructions, and not according to any speculation "opined" in
this group.

So, I too am curious, have you acquired some appropriate fuses, figured
out how to monitor the current, and been able to schedule some time off
from your other responsibilities so that you can actually work through
this puzzle once the new xformer arrives? Are you equipped to bench test
the new transformer to verify wiring color scheme before you install it?
Do you know how to test that bridge rectifier? Seems like you have a
*lot* you could be doing while waiting for the UPS guy.

I'm sorry you feel that I'm not "doing" anything or that I'm leaving you
hanging, but I'll be making the repairs on my own schedule, as time permits.
My own place of employ has me working 12 and 16 hour days, so I can't be
everywhere at once. Plus, the weather here is pleasant and there's been no
real need to run the air conditioner, and the house has two A/C units anyway so
I'm in no hurry. I don't have the fuses or fuse holders yet, but the
transformer isn't going in without them, so it will be taken care of. My
common sense tells me that I really shouldn't *have* to test and verify the
living daylights out of a new transformer, but I will most certainly get
bitched out here if I don't, so yes, that will be done. I don't really recall
the discussion about the bridge rectifier, but I'll look for it. I will be
reviewing the entire discussion and make a checklist of all the steps I need to
perform.

Anything else?