On 4/14/2011 5:28 PM, wrote:
On Thu, 14 Apr 2011 14:41:03 -0400, Jeff
wrote:

I'm assuming you mean HUMIDIFIER - and if so, you really SHOULD change
that.



No need, you did it for me.

No, I mean the humidifier should have it's OWN transformer, not
piggyback off the control transformer.

Hmmm, I thought I read somewhere that they sometimes did run off the
same transformer. I thought that was odd, but what do I know?

Ah, here it is:

http://www.doityourself.com/forum/hu...hallenges.html

Knowing nothing about this, it would sure seem even to me, better to
have separates. Particularly in the OPs case.

Jeff

Anything I post after 3AM is subject to some errors.

On 4/14/2011 12:08 AM Jeff Thies spake thus:

On 4/13/2011 8:02 PM, Stormin Mormon wrote:

I figure we'll hear back in a day or two. The fellow will have
found something wrong, put a transformer in, and everything is
good.

Amazing, haw yau change one litter, and the entier meening of the
ward changes.

Not bad Stormy. ;-)

And hey, you "fixed" your newsreader, what's with that?

No, he didn't; still as brain-damaged as ever (previously-quoted message
gets put below the sig, therefore thrown away upon replying to *his*
replies.) What made you say it was fixed?


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On Thu, 14 Apr 2011 21:12:56 -0400, Jeff Thies
wrote:

On 4/14/2011 5:28 PM, wrote:
On Thu, 14 Apr 2011 14:41:03 -0400, Jeff
wrote:

I'm assuming you mean HUMIDIFIER - and if so, you really SHOULD change
that.



No need, you did it for me.

No, I mean the humidifier should have it's OWN transformer, not
piggyback off the control transformer.

Hmmm, I thought I read somewhere that they sometimes did run off the
same transformer. I thought that was odd, but what do I know?

Ah, here it is:

http://www.doityourself.com/forum/hu...hallenges.html

Knowing nothing about this, it would sure seem even to me, better to
have separates. Particularly in the OPs case.

Jeff

Anything I post after 3AM is subject to some errors.


The control transformer is USUALLY sized pretty close to the required
size - adding a humidifier load would be adding an extra load that it
was not designed for - and if the drum sticks and the motor current
goes up???? Anybody's guess.

Now, another angle has just been thrown at us. The last 2
transformewrs blew while the AC was running - cool, not heat.

The AC will UNDOUBTABLY be a 220 volt unit. COULD be a loose neutral
situation after all - or a connection problem - depending how the
thing is wired. I HOPE the 220 for the AC is a totally different
circuit than the furnace - - - .

We REALLY do not know enough to make a definitive diagnosis.

John Robertson wrote:
Steve Turner wrote:
On 4/14/2011 2:54 PM, wrote:
On Apr 14, 2:37 pm, Steve
wrote:
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?- Hide quoted text -

- Show quoted text -

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Yep, I'll do that. It's only in cooling mode that the transformers
have failed, but I'm in Texas and we're long past the point where
we'll be needing the heater for a while, so it's hard to say whether
or not running the heat would also trigger the problem.


Steve, As said before the best thing to do is to fuse both the primary
and secondary windings.

If you have the recommended (original) transformer ratings handy that
should make it easy to figure out. For example, if the secondary (24VAC
as I recall) is rated at 1A, then the primary fuse is 1/5 of that
(24:120 - plus a fudge factor) suggesting that a 0.25A slo-blo should
last fairly well, and a 1A slo-blo on the secondary winding. If the
secondary is rated at 2A, then I'd go with a 0.5A slo-blo on the
primary, along with a 2A slo-blo on the secondary.

Two fuse holders should be fine - one for the 120VAC side and one for
the 24VAC side.

Hope this helps - at least it will reduce the cost of replacing
transformers!

John :-#)#

Hi,
Giving up for real solution? Just band aid fix? VChanging blown x-former
to blown fuse? If I am having problem like that I'd fix it for sure
dragging out all the tools I need. O'scope, clamp ammeter, DVM, etc.
Maybe it is asked already but is happening all of sudden or been like
that since the system got installed? Every symptom has cause.

On 4/14/2011 9:43 PM, wrote:
On Thu, 14 Apr 2011 21:12:56 -0400, Jeff
wrote:

On 4/14/2011 5:28 PM, wrote:
On Thu, 14 Apr 2011 14:41:03 -0400, Jeff
wrote:

I'm assuming you mean HUMIDIFIER - and if so, you really SHOULD change
that.



No need, you did it for me.

No, I mean the humidifier should have it's OWN transformer, not
piggyback off the control transformer.

Hmmm, I thought I read somewhere that they sometimes did run off the
same transformer. I thought that was odd, but what do I know?

Ah, here it is:

http://www.doityourself.com/forum/hu...hallenges.html

Knowing nothing about this, it would sure seem even to me, better to
have separates. Particularly in the OPs case.

Jeff

Anything I post after 3AM is subject to some errors.


The control transformer is USUALLY sized pretty close to the required
size - adding a humidifier load would be adding an extra load that it
was not designed for - and if the drum sticks and the motor current
goes up???? Anybody's guess.

But it wouldn't be running in AC season anyways.

Now, another angle has just been thrown at us. The last 2
transformewrs blew while the AC was running - cool, not heat.

The AC will UNDOUBTABLY be a 220 volt unit. COULD be a loose neutral
situation after all - or a connection problem - depending how the
thing is wired.

A round of tightening anything screwed down (and giving it a tug to
check), including the breaker is never a bad idea. This plausibly could
cause a big bam boom.


I HOPE the 220 for the AC is a totally different
circuit than the furnace - - - .

We REALLY do not know enough to make a definitive diagnosis.

I agree.

If the OP could unwind the transformer a bit it would help tell. Cut
out the "wrapper" and copper band and see what lies below.

Jeff

On Thu, 14 Apr 2011 19:52:52 -0600, Tony Hwang
wrote:



John Robertson wrote:
Steve Turner wrote:
On 4/14/2011 2:54 PM, wrote:
On Apr 14, 2:37 pm, Steve
wrote:
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?- Hide quoted text -

- Show quoted text -

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Yep, I'll do that. It's only in cooling mode that the transformers
have failed, but I'm in Texas and we're long past the point where
we'll be needing the heater for a while, so it's hard to say whether
or not running the heat would also trigger the problem.


Steve, As said before the best thing to do is to fuse both the primary
and secondary windings.

If you have the recommended (original) transformer ratings handy that
should make it easy to figure out. For example, if the secondary (24VAC
as I recall) is rated at 1A, then the primary fuse is 1/5 of that
(24:120 - plus a fudge factor) suggesting that a 0.25A slo-blo should
last fairly well, and a 1A slo-blo on the secondary winding. If the
secondary is rated at 2A, then I'd go with a 0.5A slo-blo on the
primary, along with a 2A slo-blo on the secondary.

Two fuse holders should be fine - one for the 120VAC side and one for
the 24VAC side.

Hope this helps - at least it will reduce the cost of replacing
transformers!

John :-#)#

Hi,
Giving up for real solution? Just band aid fix? VChanging blown x-former
to blown fuse? If I am having problem like that I'd fix it for sure
dragging out all the tools I need. O'scope, clamp ammeter, DVM, etc.
Maybe it is asked already but is happening all of sudden or been like
that since the system got installed? Every symptom has cause.
The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.

First transformer apparently lasted several years - 6 I think from
what I remember of the post. - so no, it was not a problem from the
first install.

On Thu, 14 Apr 2011 21:57:39 -0400, Jeff Thies
wrote:

On 4/14/2011 9:43 PM, wrote:
On Thu, 14 Apr 2011 21:12:56 -0400, Jeff
wrote:

On 4/14/2011 5:28 PM, wrote:
On Thu, 14 Apr 2011 14:41:03 -0400, Jeff
wrote:

I'm assuming you mean HUMIDIFIER - and if so, you really SHOULD change
that.



No need, you did it for me.

No, I mean the humidifier should have it's OWN transformer, not
piggyback off the control transformer.

Hmmm, I thought I read somewhere that they sometimes did run off the
same transformer. I thought that was odd, but what do I know?

Ah, here it is:

http://www.doityourself.com/forum/hu...hallenges.html

Knowing nothing about this, it would sure seem even to me, better to
have separates. Particularly in the OPs case.

Jeff

Anything I post after 3AM is subject to some errors.


The control transformer is USUALLY sized pretty close to the required
size - adding a humidifier load would be adding an extra load that it
was not designed for - and if the drum sticks and the motor current
goes up???? Anybody's guess.

But it wouldn't be running in AC season anyways.

Now, another angle has just been thrown at us. The last 2
transformewrs blew while the AC was running - cool, not heat.

The AC will UNDOUBTABLY be a 220 volt unit. COULD be a loose neutral
situation after all - or a connection problem - depending how the
thing is wired.

A round of tightening anything screwed down (and giving it a tug to
check), including the breaker is never a bad idea. This plausibly could
cause a big bam boom.


I HOPE the 220 for the AC is a totally different
circuit than the furnace - - - .

We REALLY do not know enough to make a definitive diagnosis.

I agree.

If the OP could unwind the transformer a bit it would help tell. Cut
out the "wrapper" and copper band and see what lies below.

Jeff
Like, any sign of overheating of the actual primary coil? and how
about the secondary??

On 4/14/2011 10:21 PM, wrote:
On Thu, 14 Apr 2011 21:57:39 -0400, Jeff
wrote:

On 4/14/2011 9:43 PM, wrote:
On Thu, 14 Apr 2011 21:12:56 -0400, Jeff
wrote:

On 4/14/2011 5:28 PM, wrote:
On Thu, 14 Apr 2011 14:41:03 -0400, Jeff
wrote:

I'm assuming you mean HUMIDIFIER - and if so, you really SHOULD change
that.



No need, you did it for me.

No, I mean the humidifier should have it's OWN transformer, not
piggyback off the control transformer.

Hmmm, I thought I read somewhere that they sometimes did run off the
same transformer. I thought that was odd, but what do I know?

Ah, here it is:

http://www.doityourself.com/forum/hu...hallenges.html

Knowing nothing about this, it would sure seem even to me, better to
have separates. Particularly in the OPs case.

Jeff

Anything I post after 3AM is subject to some errors.


The control transformer is USUALLY sized pretty close to the required
size - adding a humidifier load would be adding an extra load that it
was not designed for - and if the drum sticks and the motor current
goes up???? Anybody's guess.

But it wouldn't be running in AC season anyways.

Now, another angle has just been thrown at us. The last 2
transformewrs blew while the AC was running - cool, not heat.

The AC will UNDOUBTABLY be a 220 volt unit. COULD be a loose neutral
situation after all - or a connection problem - depending how the
thing is wired.

A round of tightening anything screwed down (and giving it a tug to
check), including the breaker is never a bad idea. This plausibly could
cause a big bam boom.


I HOPE the 220 for the AC is a totally different
circuit than the furnace - - - .

We REALLY do not know enough to make a definitive diagnosis.

I agree.

If the OP could unwind the transformer a bit it would help tell. Cut
out the "wrapper" and copper band and see what lies below.

Jeff
Like, any sign of overheating of the actual primary coil? and how
about the secondary??

Absolutely.

It's so nice and peaceful here without the SER crossposts. Ahhhh.

Jeff

On 4/14/2011 8:43 PM, wrote:
On Thu, 14 Apr 2011 21:12:56 -0400, Jeff
wrote:

On 4/14/2011 5:28 PM, wrote:
On Thu, 14 Apr 2011 14:41:03 -0400, Jeff
wrote:

I'm assuming you mean HUMIDIFIER - and if so, you really SHOULD change
that.



No need, you did it for me.

No, I mean the humidifier should have it's OWN transformer, not
piggyback off the control transformer.

Hmmm, I thought I read somewhere that they sometimes did run off the
same transformer. I thought that was odd, but what do I know?

Ah, here it is:

http://www.doityourself.com/forum/hu...hallenges.html

Knowing nothing about this, it would sure seem even to me, better to
have separates. Particularly in the OPs case.

Jeff

Anything I post after 3AM is subject to some errors.


The control transformer is USUALLY sized pretty close to the required
size - adding a humidifier load would be adding an extra load that it
was not designed for - and if the drum sticks and the motor current
goes up???? Anybody's guess.

Now, another angle has just been thrown at us. The last 2
transformewrs blew while the AC was running - cool, not heat.

The AC will UNDOUBTABLY be a 220 volt unit. COULD be a loose neutral
situation after all - or a connection problem - depending how the
thing is wired. I HOPE the 220 for the AC is a totally different
circuit than the furnace - - - .

We REALLY do not know enough to make a definitive diagnosis.

I just had a thought based on all the weird problems I've come
across over several decades. What if there is a short to one
of the control wires going to the contactor in the condensing
unit? One of the low voltage control wires could be touching
one of the legs of the 240vac line due to vibration when the
condensing unit comes on. It's just a thought. :-)

TDD

The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.


** The fuse will actually help you diagnose the problem.

If the fuse opens soon as AC power is applied - the tranny is being
overloaded.

If the fuse opens after some time because insulation in the primary side has
failed, replacement fuses will open immediately despite the secondary being
disconnected.



....Phil

Phil Allison wrote:


The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.


** The fuse will actually help you diagnose the problem.

If the fuse opens soon as AC power is applied - the tranny is being
overloaded.

If the fuse opens after some time because insulation in the primary side has
failed, replacement fuses will open immediately despite the secondary being
disconnected.



...Phil


Hmm,
This isunthinkab;e crazy idea but is the x-former being put in backward?
Rgwew i a such thing as current limiting x-formers. One thig I'd try
then I'd put in proper Wattage low value resister to lower the primary
voltage.

Phil Allison wrote:


The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.


** The fuse will actually help you diagnose the problem.

If the fuse opens soon as AC power is applied - the tranny is being
overloaded.

If the fuse opens after some time because insulation in the primary side has
failed, replacement fuses will open immediately despite the secondary being
disconnected.



...Phil



Hi,
Another question, does he keep buying same x-former over and over or
something different little havier one? Along with fuse I'd put in series
a low value proper Wattage resistor to lower the primmary voltage little
bit. Crazy thinking but hope the x-former is not put in backward.

"Tony Hwang"


This isunthinkab;e crazy idea but is the x-former being put in backward?

** You must be totally schizo.

In ,
wrote:

SNIP stuff previously said

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Measure both AC and DC current through the secondary of the transformer.
If putting a multimeter into DC current mode gets a reading around or over
50 milliamps (,05 amp), then something is wrong with the load.
If DC secondary current is near or over 200 milliamps, then,
"Houston, we have a problem"! Probably with one of the recently-mentioned
discrete diodes in a board's bridge rectifier.

Ideally, DC current through transformer windings should be zero. With
exception to specialty cases, typically involving special transformers
that use DC-handling means such as gapped cores.

If this tranny is running into problems related to DC, look for DC
through the secondary. If that turns up substantially, then the
already-mentioned 4-discrete-diode bridge rectifier on the board is
likely to be the culprit. Look for solder joints there that need touching
up, or else replace the bad diode if one is found to be bad (or all 4 of
them), or the whole board.

Depending on ability and willingness to use a soldering iron and to
troubleshoot and repair a board to component level, even with pointers
to a suspect identified set of components on the board...
It may be more practical to get a replacement board if the existing one
causes substantial DC to flow through the secondary of the transformer
that is prone to failing.

--
- Don Klipstein )

"Don Klipstein is Full of Bull "


Measure both AC and DC current through the secondary of the transformer.
If putting a multimeter into DC current mode gets a reading around or over
50 milliamps (,05 amp), then something is wrong with the load.
If DC secondary current is near or over 200 milliamps, then,
"Houston, we have a problem"!


** Simply fitting that DAMN 1/4 amp s-b fuse will tell you immediately if
any such problem exists.

Significant DC in the secondary will causes high current to flow in the
primary ( due to core saturation) and BLOW the fuse !!!

If the 1/4 amp fuse holds and the tranny does not get stinking hot - all is
OK.



..... Phil

In article ,
Jeff Thies wrote:

It's so nice and peaceful here without the SER crossposts. Ahhhh.

..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..


****wit.

Measure both AC and DC current through the secondary of the
transformer.
If putting a multimeter into DC current mode gets a reading
around or over
50 milliamps (,05 amp), then something is wrong with the load.
If DC secondary current is near or over 200 milliamps, then,
"Houston, we have a problem"!

I have been (sort of) following this conversation. I assume this
transformer also drives the contactor for the AC compressor.
Maybe there is a short in that circuit and the transformer
secondary gets shorted when the thermostat calls for cooling.

David

On Fri, 15 Apr 2011 14:04:11 +1000, Phil Allison wrote:


"Tony Hwang"


This isunthinkab;e crazy idea but is the x-former being put in
backward?

** You must be totally schizo.

Ironic statement of the year candidate!



--
Live Fast Die Young, Leave A Pretty Corpse

On 4/14/2011 10:21 PM, wrote:
On Thu, 14 Apr 2011 21:57:39 -0400, Jeff
wrote:

On 4/14/2011 9:43 PM, wrote:
On Thu, 14 Apr 2011 21:12:56 -0400, Jeff
wrote:

On 4/14/2011 5:28 PM, wrote:
On Thu, 14 Apr 2011 14:41:03 -0400, Jeff
wrote:

I'm assuming you mean HUMIDIFIER - and if so, you really SHOULD change
that.



No need, you did it for me.

No, I mean the humidifier should have it's OWN transformer, not
piggyback off the control transformer.

Hmmm, I thought I read somewhere that they sometimes did run off the
same transformer. I thought that was odd, but what do I know?

Ah, here it is:

http://www.doityourself.com/forum/hu...hallenges.html

Knowing nothing about this, it would sure seem even to me, better to
have separates. Particularly in the OPs case.

Jeff

Anything I post after 3AM is subject to some errors.


The control transformer is USUALLY sized pretty close to the required
size - adding a humidifier load would be adding an extra load that it
was not designed for - and if the drum sticks and the motor current
goes up???? Anybody's guess.

But it wouldn't be running in AC season anyways.

Now, another angle has just been thrown at us. The last 2
transformewrs blew while the AC was running - cool, not heat.

The AC will UNDOUBTABLY be a 220 volt unit. COULD be a loose neutral
situation after all - or a connection problem - depending how the
thing is wired.

A round of tightening anything screwed down (and giving it a tug to
check), including the breaker is never a bad idea. This plausibly could
cause a big bam boom.


I HOPE the 220 for the AC is a totally different
circuit than the furnace - - - .

We REALLY do not know enough to make a definitive diagnosis.

I agree.

If the OP could unwind the transformer a bit it would help tell. Cut
out the "wrapper" and copper band and see what lies below.

Jeff
Like, any sign of overheating of the actual primary coil? and how
about the secondary??

Seems like a week ago I said from the picture he posted it sure looks
like no overheating of the secondary. I've seen my share of
transformers good and bad and it still looks like an overvoltage problem
on the primary.

On 4/14/2011 9:52 PM, Tony Hwang wrote:


John Robertson wrote:
Steve Turner wrote:
On 4/14/2011 2:54 PM, wrote:
On Apr 14, 2:37 pm, Steve
wrote:
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?- Hide quoted text -

- Show quoted text -

After you put it in, measure the current and voltages in both
the primary and secondary. I'd measure them both with the
AC running and with it not running.

Also, not sure if anyone ever covered this, but when the transformers
have failed have they all been in cooling mode, heating, or both?

Yep, I'll do that. It's only in cooling mode that the transformers
have failed, but I'm in Texas and we're long past the point where
we'll be needing the heater for a while, so it's hard to say whether
or not running the heat would also trigger the problem.


Steve, As said before the best thing to do is to fuse both the primary
and secondary windings.

If you have the recommended (original) transformer ratings handy that
should make it easy to figure out. For example, if the secondary (24VAC
as I recall) is rated at 1A, then the primary fuse is 1/5 of that
(24:120 - plus a fudge factor) suggesting that a 0.25A slo-blo should
last fairly well, and a 1A slo-blo on the secondary winding. If the
secondary is rated at 2A, then I'd go with a 0.5A slo-blo on the
primary, along with a 2A slo-blo on the secondary.

Two fuse holders should be fine - one for the 120VAC side and one for
the 24VAC side.

Hope this helps - at least it will reduce the cost of replacing
transformers!

John :-#)#

Hi,
Giving up for real solution? Just band aid fix? VChanging blown x-former
to blown fuse? If I am having problem like that I'd fix it for sure
dragging out all the tools I need. O'scope, clamp ammeter, DVM, etc.
Maybe it is asked already but is happening all of sudden or been like
that since the system got installed? Every symptom has cause.

It's the first step in determining if the problem is on the primary or
secondary. Ever hear of "divide and conquer"? Fuses will hopefully cut
the troubleshooting in half. That's the first step since he can't
monitor voltage and current for hours or days at a time.

On 4/14/2011 11:18 PM, Tony Hwang wrote:


Phil Allison wrote:


The fuse is not being put forward as a solution - just to avoid
blowing the transformer while finding the real problem.


** The fuse will actually help you diagnose the problem.

If the fuse opens soon as AC power is applied - the tranny is being
overloaded.

If the fuse opens after some time because insulation in the primary
side has
failed, replacement fuses will open immediately despite the secondary
being
disconnected.



...Phil


Hmm,
This isunthinkab;e crazy idea but is the x-former being put in backward?
Rgwew i a such thing as current limiting x-formers. One thig I'd try
then I'd put in proper Wattage low value resister to lower the primary
voltage.

My word, you need sleep or something. Backwards would, oh never mind
you just proved you have no electronics knowledge.

"Tony Miklos"

** FFS - learn to TRIM !!!!!!!!!!

OK ;-)

On 4/16/2011 8:18 AM, wrote:
I would think that if it were a surge that was initiating the
failures, it would have
to be a large one to breakdown the insulation on the transformer
primary.

In a little transformer like this, the primary is very small gauge wire,
a surge could easily do it.

Tony Miklos wrote:
OK ;-)

An example of excessive trimming...

John :-#)#
--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

Top posted, too!

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"John Robertson" wrote in message
...
Tony Miklos wrote:
OK ;-)

An example of excessive trimming...

John :-#)#
--
(Please post followups or tech enquiries to the
newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T
3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video
Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On 4/16/2011 12:20 PM, Tony Miklos wrote:
On 4/16/2011 8:18 AM, wrote:
I would think that if it were a surge that was initiating the
failures, it would have
to be a large one to breakdown the insulation on the transformer
primary.

In a little transformer like this, the primary is very small gauge wire,
a surge could easily do it.

I've never seen it. In fact in my past life as a tech I rarely rarely
replaced line driven transformers. Rewound quite a few switching
transformers though.

Jeff

FYI, for those following this thread (and perhaps thinking I've abandoned it):
The only thing I have to report is that I was expecting the replacement
transformer to arrive on 04/15 (Friday), but it never did. The last status on
the UPS website (at 7:35am on 04/15) was "Mechanical failure occurred.", then
30 minutes later "Arrival Scan". From the UPS website:

"Mechanical Failu This scan indicates that an exception has occurred due to
a mechanical issue, which may cause a delay in delivery. The mechanical failure
may have occurred within a UPS facility as a result of equipment breakdown, or
while your shipment was transported by a tractor-trailer, airplane, train, or
other vehicle."

Perhaps an air traffic controller fell asleep on the job.

On Apr 17, 10:02*pm, Steve Turner
wrote:
FYI, for those following this thread (and perhaps thinking I've abandoned it):
* The only thing I have to report is that I was expecting the replacement
transformer to arrive on 04/15 (Friday), but it never did. *The last status on
the UPS website (at 7:35am on 04/15) was "Mechanical failure occurred.", then
30 minutes later "Arrival Scan". *From the UPS website:

"Mechanical Failu This scan indicates that an exception has occurred due to
a mechanical issue, which may cause a delay in delivery. The mechanical failure
may have occurred within a UPS facility as a result of equipment breakdown, or
while your shipment was transported by a tractor-trailer, airplane, train, or
other vehicle."

Perhaps an air traffic controller fell asleep on the job.

More likely this transformer burned up the truck with it.

On 4/17/2011 9:24 PM, wrote:
On Apr 17, 10:02 pm, Steve
wrote:
FYI, for those following this thread (and perhaps thinking I've abandoned it):
The only thing I have to report is that I was expecting the replacement
transformer to arrive on 04/15 (Friday), but it never did. The last status on
the UPS website (at 7:35am on 04/15) was "Mechanical failure occurred.", then
30 minutes later "Arrival Scan". From the UPS website:

"Mechanical Failu This scan indicates that an exception has occurred due to
a mechanical issue, which may cause a delay in delivery. The mechanical failure
may have occurred within a UPS facility as a result of equipment breakdown, or
while your shipment was transported by a tractor-trailer, airplane, train, or
other vehicle."

Perhaps an air traffic controller fell asleep on the job.

More likely this transformer burned up the truck with it.

LOL!

Funniest I've seen in a while, thanks for the laugh.

Steve, how's the troubleshooting going? Find a
short circuit some where? Or, have you decided to
try buying better quality transformers? I've followed
the thread, but can't remember.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


wrote in message
...


Perhaps an air traffic controller fell asleep on the job.

More likely this transformer burned up the truck with it.

Ok, *finally* some news to report!

First, I'd already procured the fuse holders and various fuses, and whilst
waiting for the replacement transformer to arrive I decided to run some
innocuous experiments on my other *working* A/C unit. Several days ago I
installed (as recommended by several) a 1/4-amp fast-acting fuse on the 115V
input side of the transformer, and the unit has been running fine ever since.
So I know that a 1/4-amp fuse will carry the load on a properly working system;
what I didn't know for *sure* was if that fuse was rated too high to protect a
transformer in the failing system...

The replacement transformer arrived this evening, so I got to work installing
connectors and testing the two circuits for continuity. I installed a 1/4-amp
fuse in the 115V primary side and (once again, as recommended) a 1.5-amp fuse
(both fast acting) on the 24V secondary side. I also hooked my meter up in
series on the secondary side to measure the current draw (I taught myself how
to do this earlier using my little Dremel tool; it draws about 1/2 amp when
spinning freely). All set, I closed the cover interlock switch to apply 115V
to the system... The red LED on the circuit board lights up momentarily, then
"piff"; the 1/4 fuse blows. Didn't get any chance to measure the current on
the meter.

Some people mentioned possible shorts in the wiring leading to the thermostat,
so my next move was to to eliminate that as a possibility. Once again, the
wiring diagrams can be found he

http://www.trane.com/webcache/un/fur...7_04012009.pdf

I removed all wires from the thermostat ("YWRGC") connector block on the
circuit board. The wiring diagram doesn't show it (at least it's not obvious
to me), but the wires that lead to the external A/C unit also connect to this
block; I removed them all (after I marked them :-) ). I also disconnected the
meter from the secondary circuit just to remove that from the equation. Once
again, I closed the cover interlock switch, and once again the 1/4-amp fuse on
the primary side opens up.

At this point, I'm 95% sure there's something wrong with the logic board, and
in anticipation of this I already had one on order; it's scheduled to arrive
tomorrow. I've toyed with the idea of swapping logic boards between the two
blower units to see if the problem follows the board (I used this approach to
isolate a similar problem on a Trane unit at my previous residence about 10
years ago; it helped, one of the boards was bad), but at this point I'm calling
it a night and will pick it up again tomorrow.

Your comments are welcome, and hopefully by tomorrow evening I'll be back in
business!

On Apr 18, 10:41*pm, Steve Turner
wrote:
Ok, *finally* some news to report!

First, I'd already procured the fuse holders and various fuses, and whilst
waiting for the replacement transformer to arrive I decided to run some
innocuous experiments on my other *working* A/C unit. *Several days ago I
installed (as recommended by several) a 1/4-amp fast-acting fuse on the 115V
input side of the transformer, and the unit has been running fine ever since.
So I know that a 1/4-amp fuse will carry the load on a properly working system;
what I didn't know for *sure* was if that fuse was rated too high to protect a
transformer in the failing system...

The replacement transformer arrived this evening, so I got to work installing
connectors and testing the two circuits for continuity. *I installed a 1/4-amp
fuse in the 115V primary side and (once again, as recommended) a 1.5-amp fuse
(both fast acting) on the 24V secondary side. *I also hooked my meter up in
series on the secondary side to measure the current draw (I taught myself how
to do this earlier using my little Dremel tool; it draws about 1/2 amp when
spinning freely). *All set, I closed the cover interlock switch to apply 115V
to the system... *The red LED on the circuit board lights up momentarily, then
"piff"; the 1/4 fuse blows. *Didn't get any chance to measure the current on
the meter.

Some people mentioned possible shorts in the wiring leading to the thermostat,
so my next move was to to eliminate that as a possibility. *Once again, the
wiring diagrams can be found he

http://www.trane.com/webcache/un/fur...product/22-166...

I removed all wires from the thermostat ("YWRGC") connector block on the
circuit board. *The wiring diagram doesn't show it (at least it's not obvious
to me), but the wires that lead to the external A/C unit also connect to this
block; I removed them all (after I marked them :-) ). *I also disconnected the
meter from the secondary circuit just to remove that from the equation. *Once
again, I closed the cover interlock switch, and once again the 1/4-amp fuse on
the primary side opens up.

At this point, I'm 95% sure there's something wrong with the logic board, and
in anticipation of this I already had one on order; it's scheduled to arrive
tomorrow. *I've toyed with the idea of swapping logic boards between the two
blower units to see if the problem follows the board (I used this approach to
isolate a similar problem on a Trane unit at my previous residence about 10
years ago; it helped, one of the boards was bad), but at this point I'm calling
it a night and will pick it up again tomorrow.

Your comments are welcome, and hopefully by tomorrow evening I'll be back in
business!

Sounds like it was many of us thought, ie that something was drawing
too
much current. I assume you didn't have the system turned on, so the
theory that it could be caused by a surge on the AC line from the
blower
motor is gone. So is the possibility of the AC contactor, as you say
you
had that disconnected too.

Did you look around the controller board and see if there is anything
that
looks like it's been running hot? Sometimes the AC to DC power
section uses parts, like a full wave rectifier, that are easily
identifiable
and can be checked. If it were something like that it might be
possible
to repair it using a part from Radio Shack. On the other hand, if the
new board is reasonable price, that will most likely solve it.

Sounds like quite a learning experience. Now, you can buy a
soldering iron station, and some resin core solder, and
search for cold solder joints and solder bridges on your
circuit board?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Steve Turner" wrote in
message ...
Ok, *finally* some news to report!

First, I'd already procured the fuse holders and various
fuses, and whilst
waiting for the replacement transformer to arrive I decided
to run some
innocuous experiments on my other *working* A/C unit.
Several days ago I
installed (as recommended by several) a 1/4-amp fast-acting
fuse on the 115V
input side of the transformer, and the unit has been running
fine ever since.
So I know that a 1/4-amp fuse will carry the load on a
properly working system;
what I didn't know for *sure* was if that fuse was rated too
high to protect a
transformer in the failing system...

The replacement transformer arrived this evening, so I got
to work installing
connectors and testing the two circuits for continuity. I
installed a 1/4-amp
fuse in the 115V primary side and (once again, as
recommended) a 1.5-amp fuse
(both fast acting) on the 24V secondary side. I also hooked
my meter up in
series on the secondary side to measure the current draw (I
taught myself how
to do this earlier using my little Dremel tool; it draws
about 1/2 amp when
spinning freely). All set, I closed the cover interlock
switch to apply 115V
to the system... The red LED on the circuit board lights up
momentarily, then
"piff"; the 1/4 fuse blows. Didn't get any chance to
measure the current on
the meter.

Some people mentioned possible shorts in the wiring leading
to the thermostat,
so my next move was to to eliminate that as a possibility.
Once again, the
wiring diagrams can be found he

http://www.trane.com/webcache/un/fur...7_04012009.pdf

I removed all wires from the thermostat ("YWRGC") connector
block on the
circuit board. The wiring diagram doesn't show it (at least
it's not obvious
to me), but the wires that lead to the external A/C unit
also connect to this
block; I removed them all (after I marked them :-) ). I
also disconnected the
meter from the secondary circuit just to remove that from
the equation. Once
again, I closed the cover interlock switch, and once again
the 1/4-amp fuse on
the primary side opens up.

At this point, I'm 95% sure there's something wrong with the
logic board, and
in anticipation of this I already had one on order; it's
scheduled to arrive
tomorrow. I've toyed with the idea of swapping logic boards
between the two
blower units to see if the problem follows the board (I used
this approach to
isolate a similar problem on a Trane unit at my previous
residence about 10
years ago; it helped, one of the boards was bad), but at
this point I'm calling
it a night and will pick it up again tomorrow.

Your comments are welcome, and hopefully by tomorrow evening
I'll be back in
business!

My impression of Trane parts (like Sears parts) is that they
are never reasonably priced.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


wrote in message
...


Your comments are welcome, and hopefully by tomorrow
evening I'll be back in
business!

Sounds like it was many of us thought, ie that
something was drawing too much current. I
assume you didn't have the system turned on,
so the theory that it could be caused by a surge
on the AC line from the blower motor is gone.
So is the possibility of the AC contactor, as
you say you had that disconnected too.

Did you look around the controller board and
see if there is anything that looks like it's been
running hot? Sometimes the AC to DC power
section uses parts, like a full wave rectifier, that
are easily identifiable and can be checked. If it
were something like that it might be possible
to repair it using a part from Radio Shack.

On the other hand, if the new board is reasonable
price, that will most likely solve it.

On 4/18/2011 9:41 PM, Steve Turner wrote:
Ok, *finally* some news to report!

First, I'd already procured the fuse holders and various fuses, and whilst
waiting for the replacement transformer to arrive I decided to run some
innocuous experiments on my other *working* A/C unit. Several days ago I
installed (as recommended by several) a 1/4-amp fast-acting fuse on the 115V
input side of the transformer, and the unit has been running fine ever since.
So I know that a 1/4-amp fuse will carry the load on a properly working system;
what I didn't know for *sure* was if that fuse was rated too high to protect a
transformer in the failing system...

The replacement transformer arrived this evening, so I got to work installing
connectors and testing the two circuits for continuity. I installed a 1/4-amp
fuse in the 115V primary side and (once again, as recommended) a 1.5-amp fuse
(both fast acting) on the 24V secondary side. I also hooked my meter up in
series on the secondary side to measure the current draw (I taught myself how
to do this earlier using my little Dremel tool; it draws about 1/2 amp when
spinning freely). All set, I closed the cover interlock switch to apply 115V to
the system... The red LED on the circuit board lights up momentarily, then
"piff"; the 1/4 fuse blows. Didn't get any chance to measure the current on the
meter.

Some people mentioned possible shorts in the wiring leading to the thermostat,
so my next move was to to eliminate that as a possibility. Once again, the
wiring diagrams can be found he

http://www.trane.com/webcache/un/fur...7_04012009.pdf


I removed all wires from the thermostat ("YWRGC") connector block on the
circuit board. The wiring diagram doesn't show it (at least it's not obvious to
me), but the wires that lead to the external A/C unit also connect to this
block; I removed them all (after I marked them :-) ). I also disconnected the
meter from the secondary circuit just to remove that from the equation. Once
again, I closed the cover interlock switch, and once again the 1/4-amp fuse on
the primary side opens up.

At this point, I'm 95% sure there's something wrong with the logic board, and
in anticipation of this I already had one on order; it's scheduled to arrive
tomorrow. I've toyed with the idea of swapping logic boards between the two
blower units to see if the problem follows the board (I used this approach to
isolate a similar problem on a Trane unit at my previous residence about 10
years ago; it helped, one of the boards was bad), but at this point I'm calling
it a night and will pick it up again tomorrow.

Your comments are welcome, and hopefully by tomorrow evening I'll be back in
business!

Dammit, I missed a step! One thing I forgot to do was verify that I was
getting 24V on the output side of the transformer when 115V was applied to the
input side. I just came back from testing for that, and now I'm confused
again. I removed both wires from the output side and connected my meter to
check for voltage, closed the interlock switch, and "piff", the 1/4-amp fuse
(my last one) blew! Apart from the fact that the input voltage comes to the
transformer via output connectors on the logic board (which are just tied
directly to input connectors on the board as far as I can see), the fuse is
blowing and the logic board isn't even a part of the equation... What do you
make of that?

On Apr 19, 9:05*am, Steve Turner
wrote:
On 4/18/2011 9:41 PM, Steve Turner wrote:





Ok, *finally* some news to report!

First, I'd already procured the fuse holders and various fuses, and whilst
waiting for the replacement transformer to arrive I decided to run some
innocuous experiments on my other *working* A/C unit. Several days ago I
installed (as recommended by several) a 1/4-amp fast-acting fuse on the 115V
input side of the transformer, and the unit has been running fine ever since.
So I know that a 1/4-amp fuse will carry the load on a properly working system;
what I didn't know for *sure* was if that fuse was rated too high to protect a
transformer in the failing system...

The replacement transformer arrived this evening, so I got to work installing
connectors and testing the two circuits for continuity. I installed a 1/4-amp
fuse in the 115V primary side and (once again, as recommended) a 1.5-amp fuse
(both fast acting) on the 24V secondary side. I also hooked my meter up in
series on the secondary side to measure the current draw (I taught myself how
to do this earlier using my little Dremel tool; it draws about 1/2 amp when
spinning freely). All set, I closed the cover interlock switch to apply 115V to
the system... The red LED on the circuit board lights up momentarily, then
"piff"; the 1/4 fuse blows. Didn't get any chance to measure the current on the
meter.

Some people mentioned possible shorts in the wiring leading to the thermostat,
so my next move was to to eliminate that as a possibility. Once again, the
wiring diagrams can be found he

http://www.trane.com/webcache/un/fur...product/22-166...

I removed all wires from the thermostat ("YWRGC") connector block on the
circuit board. The wiring diagram doesn't show it (at least it's not obvious to
me), but the wires that lead to the external A/C unit also connect to this
block; I removed them all (after I marked them :-) ). I also disconnected the
meter from the secondary circuit just to remove that from the equation. Once
again, I closed the cover interlock switch, and once again the 1/4-amp fuse on
the primary side opens up.

At this point, I'm 95% sure there's something wrong with the logic board, and
in anticipation of this I already had one on order; it's scheduled to arrive
tomorrow. I've toyed with the idea of swapping logic boards between the two
blower units to see if the problem follows the board (I used this approach to
isolate a similar problem on a Trane unit at my previous residence about 10
years ago; it helped, one of the boards was bad), but at this point I'm calling
it a night and will pick it up again tomorrow.

Your comments are welcome, and hopefully by tomorrow evening I'll be back in
business!

Dammit, I missed a step! *One thing I forgot to do was verify that I was
getting 24V on the output side of the transformer when 115V was applied to the
input side. *I just came back from testing for that, and now I'm confused
again. *I removed both wires from the output side and connected my meter to
check for voltage, closed the interlock switch, and "piff", the 1/4-amp fuse
(my last one) blew! *Apart from the fact that the input voltage comes to the
transformer via output connectors on the logic board (which are just tied
directly to input connectors on the board as far as I can see), the fuse is
blowing and the logic board isn't even a part of the equation... *What do you
make of that?- Hide quoted text -

- Show quoted text -

The first thing I would do is replace the fast blowing fuses with slow
blowing ones. I thought all along using fast ones was a bad idea.
If its an overload that's causing the problem, the slow-blow will
still
fail long before the transformer. And if it's some mysterious
voltage
spike that causing it, which I doubt, even the fast acting fuse may
not
prevent damage. It's possible the fast acting ones are getting
creamed by the initial start-up current.

I'd also consider useing a fuse temporarily thats 1.5 or 2X the
current expected. The transformer should be able to handle that
for more than the minute it takes to get a current measurement.
And if you measure voltage on the secondary, if it's an overload,
I'd expect you'd see less than 24V, as the excessive load
pulls the voltage down.

On 4/19/2011 8:47 AM, wrote:
On Apr 19, 9:05 am, Steve
wrote:
On 4/18/2011 9:41 PM, Steve Turner wrote:





Ok, *finally* some news to report!

First, I'd already procured the fuse holders and various fuses, and whilst
waiting for the replacement transformer to arrive I decided to run some
innocuous experiments on my other *working* A/C unit. Several days ago I
installed (as recommended by several) a 1/4-amp fast-acting fuse on the 115V
input side of the transformer, and the unit has been running fine ever since.
So I know that a 1/4-amp fuse will carry the load on a properly working system;
what I didn't know for *sure* was if that fuse was rated too high to protect a
transformer in the failing system...

The replacement transformer arrived this evening, so I got to work installing
connectors and testing the two circuits for continuity. I installed a 1/4-amp
fuse in the 115V primary side and (once again, as recommended) a 1.5-amp fuse
(both fast acting) on the 24V secondary side. I also hooked my meter up in
series on the secondary side to measure the current draw (I taught myself how
to do this earlier using my little Dremel tool; it draws about 1/2 amp when
spinning freely). All set, I closed the cover interlock switch to apply 115V to
the system... The red LED on the circuit board lights up momentarily, then
"piff"; the 1/4 fuse blows. Didn't get any chance to measure the current on the
meter.

Some people mentioned possible shorts in the wiring leading to the thermostat,
so my next move was to to eliminate that as a possibility. Once again, the
wiring diagrams can be found he

http://www.trane.com/webcache/un/fur...product/22-166...

I removed all wires from the thermostat ("YWRGC") connector block on the
circuit board. The wiring diagram doesn't show it (at least it's not obvious to
me), but the wires that lead to the external A/C unit also connect to this
block; I removed them all (after I marked them :-) ). I also disconnected the
meter from the secondary circuit just to remove that from the equation. Once
again, I closed the cover interlock switch, and once again the 1/4-amp fuse on
the primary side opens up.

At this point, I'm 95% sure there's something wrong with the logic board, and
in anticipation of this I already had one on order; it's scheduled to arrive
tomorrow. I've toyed with the idea of swapping logic boards between the two
blower units to see if the problem follows the board (I used this approach to
isolate a similar problem on a Trane unit at my previous residence about 10
years ago; it helped, one of the boards was bad), but at this point I'm calling
it a night and will pick it up again tomorrow.

Your comments are welcome, and hopefully by tomorrow evening I'll be back in
business!

Dammit, I missed a step! One thing I forgot to do was verify that I was
getting 24V on the output side of the transformer when 115V was applied to the
input side. I just came back from testing for that, and now I'm confused
again. I removed both wires from the output side and connected my meter to
check for voltage, closed the interlock switch, and "piff", the 1/4-amp fuse
(my last one) blew! Apart from the fact that the input voltage comes to the
transformer via output connectors on the logic board (which are just tied
directly to input connectors on the board as far as I can see), the fuse is
blowing and the logic board isn't even a part of the equation... What do you
make of that?- Hide quoted text -

- Show quoted text -

The first thing I would do is replace the fast blowing fuses with slow
blowing ones. I thought all along using fast ones was a bad idea.
If its an overload that's causing the problem, the slow-blow will
still
fail long before the transformer. And if it's some mysterious
voltage
spike that causing it, which I doubt, even the fast acting fuse may
not
prevent damage. It's possible the fast acting ones are getting
creamed by the initial start-up current.

I'd also consider useing a fuse temporarily thats 1.5 or 2X the
current expected. The transformer should be able to handle that
for more than the minute it takes to get a current measurement.
And if you measure voltage on the secondary, if it's an overload,
I'd expect you'd see less than 24V, as the excessive load
pulls the voltage down.

Sure, I can try some different fuses (but I have to go make a run to buy some;
that might not happen until later today). But now with the connectors removed
from the 24V output side of the transformer, haven't I removed all the load?
Wouldn't that mean there is something wrong with the input side of the circuit?

On 4/19/2011 9:05 AM, Steve Turner wrote:
On 4/18/2011 9:41 PM, Steve Turner wrote:
Ok, *finally* some news to report!

First, I'd already procured the fuse holders and various fuses, and
whilst
waiting for the replacement transformer to arrive I decided to run some
innocuous experiments on my other *working* A/C unit. Several days ago I
installed (as recommended by several) a 1/4-amp fast-acting fuse on
the 115V
input side of the transformer, and the unit has been running fine
ever since.
So I know that a 1/4-amp fuse will carry the load on a properly
working system;
what I didn't know for *sure* was if that fuse was rated too high to
protect a
transformer in the failing system...

The replacement transformer arrived this evening, so I got to work
installing
connectors and testing the two circuits for continuity. I installed a
1/4-amp
fuse in the 115V primary side and (once again, as recommended) a
1.5-amp fuse
(both fast acting) on the 24V secondary side. I also hooked my meter
up in
series on the secondary side to measure the current draw (I taught
myself how
to do this earlier using my little Dremel tool; it draws about 1/2
amp when
spinning freely). All set, I closed the cover interlock switch to
apply 115V to
the system... The red LED on the circuit board lights up momentarily,
then
"piff"; the 1/4 fuse blows. Didn't get any chance to measure the
current on the
meter.

Some people mentioned possible shorts in the wiring leading to the
thermostat,
so my next move was to to eliminate that as a possibility. Once
again, the
wiring diagrams can be found he

http://www.trane.com/webcache/un/fur...7_04012009.pdf



I removed all wires from the thermostat ("YWRGC") connector block on the
circuit board. The wiring diagram doesn't show it (at least it's not
obvious to
me), but the wires that lead to the external A/C unit also connect to
this
block; I removed them all (after I marked them :-) ). I also
disconnected the
meter from the secondary circuit just to remove that from the
equation. Once
again, I closed the cover interlock switch, and once again the
1/4-amp fuse on
the primary side opens up.

At this point, I'm 95% sure there's something wrong with the logic
board, and
in anticipation of this I already had one on order; it's scheduled to
arrive
tomorrow. I've toyed with the idea of swapping logic boards between
the two
blower units to see if the problem follows the board (I used this
approach to
isolate a similar problem on a Trane unit at my previous residence
about 10
years ago; it helped, one of the boards was bad), but at this point
I'm calling
it a night and will pick it up again tomorrow.

Your comments are welcome, and hopefully by tomorrow evening I'll be
back in
business!

Dammit, I missed a step! One thing I forgot to do was verify that I
was getting 24V on the output side of the transformer when 115V was
applied to the input side. I just came back from testing for that,
and now I'm confused again. I removed both wires from the output side
and connected my meter to check for voltage, closed the interlock
switch, and "piff", the 1/4-amp fuse (my last one) blew! Apart from
the fact that the input voltage comes to the transformer via output
connectors on the logic board (which are just tied directly to input
connectors on the board as far as I can see), the fuse is blowing and
the logic board isn't even a part of the equation... What do you make
of that?
Steve,

I am (I think) the person who originally suggested getting the inline
fuse holder and fuses from Radio Shack, and am glad to see you are
pursuing this. Since you have a disconnected secondary, and a fused
primary, and the transformer blows the 1/4 amp fuse, it certainly sounds
like the primary supply voltage is wrong. Have you actually measured the
primary voltage and found it to be about 110 VAC? If so, then the
transformer, with no secondary load, must be defective if it immediately
blows a 1/4 amp fuse with no secondary load, unless for some reason your
logic board is providing some odd waveform other than purely alternating
60 Hz power. Perhaps, for example, some big DC voltage is also present?

It is very hard to believe that the several transformers you have tried
are ALL defective. I am way more suspicious of the supply voltage.

On 4/19/2011 9:51 AM, Smarty wrote:
On 4/19/2011 9:05 AM, Steve Turner wrote:
On 4/18/2011 9:41 PM, Steve Turner wrote:
Ok, *finally* some news to report!

First, I'd already procured the fuse holders and various fuses, and whilst
waiting for the replacement transformer to arrive I decided to run some
innocuous experiments on my other *working* A/C unit. Several days ago I
installed (as recommended by several) a 1/4-amp fast-acting fuse on the 115V
input side of the transformer, and the unit has been running fine ever since.
So I know that a 1/4-amp fuse will carry the load on a properly working system;
what I didn't know for *sure* was if that fuse was rated too high to protect a
transformer in the failing system...

The replacement transformer arrived this evening, so I got to work installing
connectors and testing the two circuits for continuity. I installed a 1/4-amp
fuse in the 115V primary side and (once again, as recommended) a 1.5-amp fuse
(both fast acting) on the 24V secondary side. I also hooked my meter up in
series on the secondary side to measure the current draw (I taught myself how
to do this earlier using my little Dremel tool; it draws about 1/2 amp when
spinning freely). All set, I closed the cover interlock switch to apply 115V to
the system... The red LED on the circuit board lights up momentarily, then
"piff"; the 1/4 fuse blows. Didn't get any chance to measure the current on the
meter.

Some people mentioned possible shorts in the wiring leading to the thermostat,
so my next move was to to eliminate that as a possibility. Once again, the
wiring diagrams can be found he

http://www.trane.com/webcache/un/fur...7_04012009.pdf



I removed all wires from the thermostat ("YWRGC") connector block on the
circuit board. The wiring diagram doesn't show it (at least it's not obvious to
me), but the wires that lead to the external A/C unit also connect to this
block; I removed them all (after I marked them :-) ). I also disconnected the
meter from the secondary circuit just to remove that from the equation. Once
again, I closed the cover interlock switch, and once again the 1/4-amp fuse on
the primary side opens up.

At this point, I'm 95% sure there's something wrong with the logic board, and
in anticipation of this I already had one on order; it's scheduled to arrive
tomorrow. I've toyed with the idea of swapping logic boards between the two
blower units to see if the problem follows the board (I used this approach to
isolate a similar problem on a Trane unit at my previous residence about 10
years ago; it helped, one of the boards was bad), but at this point I'm calling
it a night and will pick it up again tomorrow.

Your comments are welcome, and hopefully by tomorrow evening I'll be back in
business!

Dammit, I missed a step! One thing I forgot to do was verify that I was
getting 24V on the output side of the transformer when 115V was applied to
the input side. I just came back from testing for that, and now I'm confused
again. I removed both wires from the output side and connected my meter to
check for voltage, closed the interlock switch, and "piff", the 1/4-amp fuse
(my last one) blew! Apart from the fact that the input voltage comes to the
transformer via output connectors on the logic board (which are just tied
directly to input connectors on the board as far as I can see), the fuse is
blowing and the logic board isn't even a part of the equation... What do you
make of that?
Steve,

I am (I think) the person who originally suggested getting the inline fuse
holder and fuses from Radio Shack, and am glad to see you are pursuing this.
Since you have a disconnected secondary, and a fused primary, and the
transformer blows the 1/4 amp fuse, it certainly sounds like the primary supply
voltage is wrong. Have you actually measured the primary voltage and found it
to be about 110 VAC? If so, then the transformer, with no secondary load, must
be defective if it immediately blows a 1/4 amp fuse with no secondary load,
unless for some reason your logic board is providing some odd waveform other
than purely alternating 60 Hz power. Perhaps, for example, some big DC voltage
is also present?

It is very hard to believe that the several transformers you have tried are ALL
defective. I am way more suspicious of the supply voltage.

Yes, the supply voltage is correct (actually, it's 120V, which is what pretty
much every other "115V" circuit in the house is receiving). To be safe this
time, I ordered more than one replacement transformer (they were cheap) and I
just hooked another one to a completely different circuit (on my workbench)
with a 1/2-amp fast-acting fuse on the input side and no load on the secondary,
and the fuse held and I got a constant 26V on the output side. I will be going
to procure some more 1/4-amp fuses (both fast and slow blow) and I will remove
the exact transformer I intend to use from the blower unit (it has all the
right connectors attached to the wires) and attempt the same experiment on my
workbench using both 1/2-amp and 1/4-amp fuses just to be sure I can completely
rule out the transformer. If that works, I will take that same transformer
back to the blower unit and run the same test there, bypassing the circuit
board entirely. More to come...