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How would it be acting if faulty?
Just a thought,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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-1666-07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?
a bad start cap would not affect the 24v control transformer,that just"Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-1666-
07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?
a line voltage monitor may be needed to see if there's some short-termJust a thought,
When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?
The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.
robb
"robb" <some@where.on.net> wrote in
news:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
"Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-1666-
07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?
a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.
Transient overvoltages of less than 20% or there-abouts are unlikelyJust a thought,
When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?
The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.
robb
a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets converted
to heat,not output voltage. a DMM will not show line distortion or short
term overvoltages.
are the wires burned close to the transformer,or over their entire length?
I peeled the insulation back from the hot and neutral wires and the burning"robb"<some@where.on.net> wrote in
news:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
"Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-1666-
07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?
a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.
Just a thought,
When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?
The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.
robb
a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets converted
to heat,not output voltage. a DMM will not show line distortion or short
term overvoltages.
are the wires burned close to the transformer,or over their entire length?
So the problem is the joint of the transformer wiring to the lugs. TheyOn 4/9/2011 7:29 PM, Jim Yanik wrote:
"robb"<some@where.on.net> wrote in
news:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
"Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-1666-
07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?
a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.
Just a thought,
When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?
The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.
robb
a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may
determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets
converted
to heat,not output voltage. a DMM will not show line distortion or short
term overvoltages.
are the wires burned close to the transformer,or over their entire
length?
I peeled the insulation back from the hot and neutral wires and the
burning only occurred right at the terminals, no more than 1/4" into the
wiring.
Yep, My A/C unit blew another transformer. Pictures (and wiring diagram)
here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
http://www.trane.com/webcache/un/furnaces%20%28furn%29/product/22-1666-07_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).
Is that a dual primary 115V (230V) xformer? Did you wire both primariesOn 4/9/2011 7:29 PM, Jim Yanik wrote:
"robb"<some@where.on.net> wrote in
news:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
"Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-1666-
07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?
a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.
Just a thought,
When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?
The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.
robb
a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets converted
to heat,not output voltage. a DMM will not show line distortion or short
term overvoltages.
are the wires burned close to the transformer,or over their entire length?
I peeled the insulation back from the hot and neutral wires and the burning
only occurred right at the terminals, no more than 1/4" into the wiring.
firstly an in-line fuse of say 1/4 amp ....
1 uF sounds a little high."robb"
Yep, My A/C unit blew another transformer. Pictures (and wiring diagram)
here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
http://www.trane.com/webcache/un/furnaces%20%28furn%29/product/22-1666-07_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).
** From the damage to the tranny visible in the photos - the primary has
developed an internal short ( due to insulation failure) and since there is
no fuse link in series, the resulting current was high enough to make an
exposed wire leading to the terminals explode.
An internal short could develop due to heat alone because of an overload on
the tranny - but this requires a fault to exist on the secondary side which
seems not to be the case.
High voltage spikes on the primary could also cause insulation failure
leading to the damage seen in the pics - lightning does this sort of thing.
So also could back emfs from the blower fan if the is a bad connection in
the AC supply feed.
I suggest you provide the next replacement for that vulnerable tranny with
some "protection" - firstly an in-line fuse of say 1/4 amp AND a
capacitor wired across the primary of say 1uF rated for continuous use
across the AC supply.
If there is an overload on the tranny, the fuse will blow.
The 1uF capacitor should suppress spike voltages enough to save the tranny
from harm.
..... Phil
Everything I see on the diagrams says this is a HSI (Hot Surface"Mark" wrote in message
news:fe82a1bf-396e-4db1-96be-bdbc0d47798e@e9g2000vbk.googlegroups.com...
To OP
this is a long shot but...
I noticed on the Trane wiring diagram that you posted that the
connections for the IGNITION circuit are shown to be near to the
connections for the primary of the transformer.
snip
Mark
This thread started on a.h.r (alt.home.repair) and I'm not sure the OPIs that a dual primary 115V (230V) xformer? Did you wire both primaries
in parallel for 115V operation?
Grant.
It also could be powering a thermostat. Some of them will take power"robb" <s...@where.on.net> wrote innews:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
"Steve Turner" wrote in messagenews:inoakf$qin$1@dont-email.me...
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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-1666-
07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?
a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.
That's a good idea too.Just a thought,
When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?
The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.
I don't see how he could have a waveform that is so out of shape thatrobb
a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets converted
to heat,not output voltage.
a DMM will not show line distortion or short
term overvoltages.
are the wires burned close to the transformer,or over their entire length?
--
Jim Yanik
jyanik
at
localnet
dot com- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -
another poster on the alt.home.repair NG made that suggestion/comment.On Sat, 09 Apr 2011 20:55:37 -0500, Steve Turner
bbqboyee@swtacobell.net.invalid> wrote:
On 4/9/2011 7:29 PM, Jim Yanik wrote:
"robb"<some@where.on.net> wrote in
news:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
"Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-16
66- 07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and
I never tried to force the system to come on so I could monitor
it; that was probably a mistake. Unfortunately, I was also absent
from the premises during the extended times when the unit was most
likely operational, so that didn't help either. However, my family
tells me that it WAS working and cooling the house rather nicely,
for at least a day, perhaps two. I'm getting 115V in all the
right places, so it doesn't look like an over-voltage condition to
me. Perhaps it's an overheating condition? It looks to me like
the only real load on this circuit is the blower motor; could the
motor be causing this? The blower spins freely when I turn it by
hand. Start capacitor on the motor maybe? Relay on the control
board perhaps?
a bad start cap would not affect the 24v control transformer,that
just powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.
Just a thought,
When you put the new transformer in does the "Diagnostic Light"
LED turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?
The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test
with test equipment.
robb
a line voltage monitor may be needed to see if there's some
short-term overvoltage applied to the transformer,and a oscilloscope
may determine if the input waveform is sinusoidal or
otherwise,because 60hz iron core tranformers don't like extreme
distortion on their input,it gets converted to heat,not output
voltage. a DMM will not show line distortion or short term
overvoltages. are the wires burned close to the transformer,or over
their entire length?
I peeled the insulation back from the hot and neutral wires and the
burning only occurred right at the terminals, no more than 1/4" into
the wiring.
Is that a dual primary 115V (230V) xformer? Did you wire both
primaries in parallel for 115V operation?
Grant.
David,"Mark" wrote in message
news:fe82a1bf-396e-4db1-96be-bdbc0d47798e@e9g2000vbk.googlegroups.com...
To OP
this is a long shot but...
I noticed on the Trane wiring diagram that you posted that the
connections for the IGNITION circuit are shown to be near to the
connections for the primary of the transformer.
snip
Mark
Everything I see on the diagrams says this is a HSI (Hot Surface
Igniter) type of furnace. There is no high voltage in that type
of igniter.
David
"robb"
Yep, My A/C unit blew another transformer. Pictures (and wiring
diagram)
here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
http://www.trane.com/webcache/un/furnaces%20%28furn%29/product/22-1666-07_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).
** From the damage to the tranny visible in the photos - the primary has
developed an internal short ( due to insulation failure) and since there
is
no fuse link in series, the resulting current was high enough to make an
exposed wire leading to the terminals explode.
An internal short could develop due to heat alone because of an overload
on
the tranny - but this requires a fault to exist on the secondary side
which
seems not to be the case.
High voltage spikes on the primary could also cause insulation failure
leading to the damage seen in the pics - lightning does this sort of
thing.
So also could back emfs from the blower fan if the is a bad connection in
the AC supply feed.
I suggest you provide the next replacement for that vulnerable tranny
with
some "protection" - firstly an in-line fuse of say 1/4 amp AND a
capacitor wired across the primary of say 1uF rated for continuous use
across the AC supply.
If there is an overload on the tranny, the fuse will blow.
The 1uF capacitor should suppress spike voltages enough to save the
tranny
from harm.
1 uF sounds a little high.
** Think again.I would think .01 uF at 400V would be a better bet.
** Bad idea.Or an MOV (metal oxide varistor) or three (across the line and then from
each side to ground).
** Not on the AC supply they don't.I don't think this is a voltage spike problem though. Voltage spikes take
out other components first.
Hi John, fancy meeting you here! Wait, I didn't realize this is crossSteve Turner wrote:
On 4/9/2011 7:29 PM, Jim Yanik wrote:
"robb"<some@where.on.net> wrote in
news:WfKdnQOvu_d2bz3QnZ2dnUVZ_uadnZ2d@earthlink.com:
"Steve Turner" wrote in message news:inoakf$qin$1@dont-email.me...
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) here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
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/furnaces%20%28furn%29/product/22-1666-
07_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.
I never got a real chance to test out the system after installing
this third transformer. We had cool weather for several days, and I
never tried to force the system to come on so I could monitor it;
that was probably a mistake. Unfortunately, I was also absent from
the premises during the extended times when the unit was most likely
operational, so that didn't help either. However, my family tells me
that it WAS working and cooling the house rather nicely, for at
least a day, perhaps two. I'm getting 115V in all the right places,
so it doesn't look like an over-voltage condition to me. Perhaps
it's an overheating condition? It looks to me like the only real
load on this circuit is the blower motor; could the motor be causing
this? The blower spins freely when I turn it by hand. Start
capacitor on the motor maybe? Relay on the control board perhaps?
a bad start cap would not affect the 24v control transformer,that just
powers the controller board and relays.
either something is loading the transformer or a problem with input
voltage.
Just a thought,
When you put the new transformer in does the "Diagnostic Light" LED
turn on ?
Does the LED blink or flash in one of the patterns indicated in the
"diagnostic codes" section that you posted a link to ?
The "diagnostic codes" imply that the control board can detect
several of the problems mentioned by others.
Maybe a good starting point as there is not enough time to test with
test equipment.
robb
a line voltage monitor may be needed to see if there's some short-term
overvoltage applied to the transformer,and a oscilloscope may
determine if
the input waveform is sinusoidal or otherwise,because 60hz iron core
tranformers don't like extreme distortion on their input,it gets
converted
to heat,not output voltage. a DMM will not show line distortion or short
term overvoltages.
are the wires burned close to the transformer,or over their entire
length?
I peeled the insulation back from the hot and neutral wires and the
burning only occurred right at the terminals, no more than 1/4" into
the wiring.
So the problem is the joint of the transformer wiring to the lugs. They
may have cold solder joints, or the lug may be slightly loose - enough
to crack the solder connection over time. Your transformer may still be
good!
When you are examining the transformer wire make sure it is stripped
enough to get good solder coverage. Burn off the insulation (enamel) -
do not sand, scrape, or try to erode it because if you scratch the wire
it will break at the scratch.
Re-solder the transformer connectors after first making sure the wire
has at least two complete wraps around the solder lug and the solder
makes a good meniscus joint to the wire and lug. Also use a good grade
of solder, not regular 60/40, find some 63/37 solder (Kester is best) -
this solder resists cold solder joints due to movement when cooling by
solidifying very fast.
John :-#)#
Oh my gawd, someone agrees with me. Looking at the picture says a lot."robb"
Yep, My A/C unit blew another transformer. Pictures (and wiring diagram)
here:
http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
http://www.trane.com/webcache/un/furnaces%20%28furn%29/product/22-1666-07_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).
** From the damage to the tranny visible in the photos - the primary has
developed an internal short ( due to insulation failure) and since there is
no fuse link in series, the resulting current was high enough to make an
exposed wire leading to the terminals explode.
An internal short could develop due to heat alone because of an overload on
the tranny - but this requires a fault to exist on the secondary side which
seems not to be the case.
** Why ?????** From the damage to the tranny visible in the photos - the primary has
developed an internal short ( due to insulation failure) and since there
is
no fuse link in series, the resulting current was high enough to make an
exposed wire leading to the terminals explode.
An internal short could develop due to heat alone because of an overload
on
the tranny - but this requires a fault to exist on the secondary side
which
seems not to be the case.
Oh my gawd, someone agrees with me. Looking at the picture says a lot.
Burnt on the primary side, looks like new on the secondary. And this is
the third transformer with an open primary!
I don't know about a the 1uF cap, seems way too high
** Nothing like doing the old Ostrich trick when the brain gets overloaded.so I'll delete what was below and pretend I didn't see it.