Blew another damn transformer on my Trane XB80
Steve Turner
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?
David Nebenzahl
> 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.
How 'bout installing an in-line fuse next time you replace the xfmr? I'd
put it on the secondary side. That way, if there is an overload, the
fuse will blow instead.
--
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*?)
Tony Hwang
Hi,
Is the x-former gets hot when in use? Unless it is under rated for the
application, it should npot blow so often. It is just 120-24V AC step
down tranny. Buy one of hevier one(bigger size and really heavier in
weight than stock) If it blows again, something on the load side is wrong.
dpb
>
>
> Steve Turner wrote:
>> A continuation of the "Why does the 115V->24V transformer keep blowing
>> on my Trane XB80?" discussion I started on 04/02/2011.
> ... Buy one of hevier one(bigger size and really heavier in
> weight than stock) If it blows again, something on the load side is wrong.
I'd venture something is already wrong...
--
hr(bob) hofmann@att.net
Put a voltmeter on the secondary side and measure the voltage when it
is not running. THen turn on the AC and see what the secondary
voltage does. IF it is supposed to operate a relay, and the current
draw is appropriate for the size transformer you have, I would not
expect the voltage to drop by more than 20%. Then leaving the AC on,
for at least 1/2 hour, keep monitoring the transformer tempoerature.
If it is a gradual heating, see how hot it gets. If there is a severe
overload, the transform may blow out before it even gets hot to the
touch. If it just gets warm over 10 - 20 minutes, then that is
probably about normal. IF you can find out what the correct current
drain is supposed to be, I would go for a transformer with double that
amperage ratinbg just ot be ultra-safe. But you have to be there and
monitor things, coming back 48 hours later is not going to work!!!
Tony Miklos
> 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).
Three times it fried the primary? I'd guess it's getting 240vac at
times. It's very unusual for the primary to go bad from a short on the
secondary side, and the picture shows that the secondary wasn't
overheated like the primary was. Where's all those electricians talking
about an open neutrals when you need them? If it measures 120vac tie a
light bulb into the primary side and leave it where it can be seen.
Have the family let you know if it ever gets brighter than normal. Or
better yet, call a pro.
Steve Turner
Thinking maybe I should spring for a transformer with a manual reset, like this
one:
Would that protect me from having to replace the damn transformer every time?
It looks like the circuit breaker is on the 24V output side; I'm a little fuzzy
on how that would protect the input side of the transformer...?
Steve Turner
That very thought crossed my mind, but I'm not sure how that could happen. The
unit is on a dedicated 115V circuit tied to a single-pole breaker. Where would
the possibility exist for the neutral to become hot? In the breaker box?
David Nebenzahl
Why in the world would you think you need to protect the primary side?
Unless you've got a *really* weird problem--namely, severe overvoltage
spikes--there's no way the damage is coming from that side. It's got to
be because of overcurrent on the secondary side.
Unless there's something really messed up with your house's wiring ...
Steve Turner
Well I'm no electrician so I don't *know*. What I really mean is that I want
to protect *myself* from having to drop $20 or $30 a pop on a half-dozen
transformers while I'm trying to figure out what's wrong. So again, would the
transformer referenced above protect me from that? Many helpful things are
being suggested, but unfortunately they all seem to require testing the unit
while it's operational, and I can't do that unless I have a working transformer
installed.
> Unless you've got a *really* weird problem--namely, severe overvoltage
> spikes--there's no way the damage is coming from that side. It's got to be
> because of overcurrent on the secondary side.
Ok, and how does that condition come into existence? Is there anything in the
wiring diagram that jumps out at you as a potential candidate? I have two
identical Trane AC/furnace units; one upstairs and one down. Should I swap
control boards between units to see if the problem follows the control board?
> Unless there's something really messed up with your house's wiring ...
The house is only six years old. Nothing's changed in terms of wiring and
everything's been fine up until now.
Smitty Two
Steve Turner <bbqb...@swtacobell.net.invalid> wrote:
<snip>
You might start at the beginning and make sure everything is hooked up
correctly. I mean, once you spring for yet another transformer. For
example, your latest fried transformer has six wires. The schematic
shows the secondary wire colors as blue and red. Given the location of
the blue and red wires on the pic of the transformer you have, that's
not quite intuitive.
And, it may not even be right. So I'd buy a new one, and check some
voltages on the bench. Put 120 into the black and white, and then
measure every other pair to make sure you understand which two wires are
really putting out 24 V.
Obviously, when you go to install it, clip and shrink tube the unused
wires, and make sure that leads are dressed so that they won't short
anywhere.
Then I'd be monitoring the damn thing, preferably with a voltmeter
perhaps on the primary and an ammeter on the secondary.
Smitty Two
<prestwhich-7849E...@mx02.eternal-september.org>,
Smitty Two <prest...@earthlink.net> wrote:
And I'll add that I'd treat this as a single failure. The first
transformer lasted 6 years and probably only has an open $2 thermal
fuse. The second transformer was a cheap knockoff. So don't worry about
those. Focus on this one. The arcing looks like a hard short.
And note the note on the wiring diagram about minding the hot lead going
to the correct place. Verify the hot lead independently of the damn wire
color.
Tony Miklos
Look at the picture. The primary side has been overheated, the
secondary side looks fine. Looks like an over voltage problem to me.
Tony Miklos
It happens all the time.
Bill
news:inomp2$vc8$1...@dont-email.me...
A neutral in a breaker box could have a loose connection. These
connections can heat up and cool down as more/less electricity is used
on the panel in question. And there may be a point where the
connection fails momentarily or arcs. Then if you lose the neutral
connection, 120 volt circuits become 240 volt circuits via other
circuits turned on in the panel on the other leg.
The solution to that problem is usually to have the electric company
or electrician retorque the main panel lug nuts to the panel
manufacturers tightness specifications in inch lbs. Note POWER IS
ALWAYS HOT TO THESE CONNECTIONS and this is NOT a DIY thing!
A similar problem can be with what is called a MWBC or Multi-Wire
Branch Circuit. These are 2 separate 120 V circuits run to the same
area that share one neutral wire. So 2 hots and 1 neutral coming from
the breaker panel. A loose neutral connection with that one wire and
same problem.
When the entire panel is having this problem, you would see lights get
brighter as the problem occurs.
If just a problem with one MWBC, then only those circuits would have
the problem.
tra...@optonline.net
I'd agree. Responding to his first post and before he put this
latest transformer in I recommended measuring
how many amps are being drawn on the low voltage side.
This is electricity 101. So, he comes here asking for advice
and instead of listening, he justs puts another transformer in
and blows it too..... Go figure. Time to either get educated
or hire a pro.
tra...@optonline.net
> "Steve Turner" <bbqbo...@swtacobell.net.invalid> wrote in message
>
> news:inomp2$vc8$1...@dont-email.me...
>
>
>
>
>
> > On 4/8/2011 10:16 PM, Tony Miklos wrote:
> >> On 4/8/2011 8:52 PM, Steve Turner wrote:
> >>> 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):
>
>
> - Show quoted text -
The problem with that theory is that the 120V circuit that supplies
power
to the transformer also powers the rest of the furnace, ie the inducer
blower, main blower, etc. If it were getting 240V, one would think by
now one of those other components would have failed. Also, with
240V it would be delivering 48V to the logic board, which one would
think would have opened a fuse on it or destroyed some electronics
by now.
I can't say I can make much sense of what is going on either. But
until someone with some basic electric skills capable of taking
some measurements looks at it, I doubt we're gonna fix it by
remote analysis.
Mark
wrote:
To OP,
I'm not going to wade through all the previous posts...
you pictures show a transformer with 6 leads.
the wiring diagrams show a transformer with 4 leads
how are you connecting the transformer..
Do you have a voltmeter... when you connected the transformer does it
blow up immediately or after a time?
Did you check the pri and sec voltages..
A failure like shown in the pic with big black scorch marks would
indicate a MAJOR overload like you have connected the transformer
completely wrong ...or there is some metal box or something that
shorts to the terminals. Does the main breaker blow too?
Find a ham radio guy or someone that knows a bit about electricity to
help you.
Mark
The Daring Dufas
I wonder if our intrepid OP has done the basics involved in
troubleshooting instead of flitting around from place to place?
In the case of a power problem, you always start at the source by
measuring voltage and current. It could be a very simple problem
like a bit of insulation skinned off a thermostat wire that only
shorts out when everything is buttoned up and vibration from the
running unit causes the short circuit. If you ever watched the TV
program MASH, you would see the surgeons run the intestines looking
for a nick in the wall of the organ. Wiring is the same way sometimes.
I'll inspect the wiring and often find a small cut or tiny area where
insulation is missing and sometimes the wire is bent over a sharp edge
of the cabinet where it's fine until you close things up. I wonder if
the supply voltage to the transformer is what it's supposed to be? Most
domestic household air handler/furnaces are powered by 120vac but some
may require 240vac if there are electric heat strips. I would check the
voltage feeding the transformer first.
TDD
The Daring Dufas
I don't understand the lack of a temporary fuse or circuit breaker in
troubleshooting this unit. The supply houses sell a little push to reset
breaker that can be installed in series with the transformer. Heck, a
box of fuses is less expensive than a transformer. :-)
TDD
Steve Turner
In case you hadn't noticed, I've been getting LOTS of (much appreciated) advice
from many people, but it's also been very contradictory with no single
suggested approach. It's been an interesting and informative discussion, and
I've been happy that nobody's been a jerk about it... until *now*. And I DID
listen; plenty of people suggested that the original transformer was likely to
be under-rated and to replace it with something more heavy-duty. Also, it
seems to me that having a working transformer is a pre-requisite to following
your advice of measuring the amp draw on the low voltage side, no?
Unfortunately, time constraints prevented me from being there to perform those
measurements when the unit was running, and unfortunately again the transformer
blew in my absence. But of course, I'm repeating myself...
Steve Turner
Yes, I've done all those things. The supply voltage is fine. I've inspected
the wiring at great length and can find no evidence of problems; it all looks
pristine. It's a gas furnace, and there are no 220 circuits running anywhere
near that area of the house.
Thanks.
The Daring Dufas
Steve I really hope you can figure out the problem with the furnace and
I can understand the bit about time constraints. Installing a fuse in
series with with either side of the transformer is cheap insurance to
keep from losing another transformer. The fuse holders are inexpensive
and it's a lot less of a hassle to replace a blown fuse.
TDD
Steve Turner
Yes, I would be more than willing to do that, but my electricity training is
not quite up to the 101 level that trader4 seems to think I should have; can
you suggest a specific fuse rating that I should use? Thanks!
tra...@optonline.net
wrote:
> On 4/9/2011 9:12 AM, trad...@optonline.net wrote:
>
>
>
>
>
> > On Apr 8, 10:05 pm, dpb<n...@non.net> wrote:
> >> On 4/8/2011 8:44 PM, Tony Hwang wrote:
>
> >>> Steve Turner wrote:
> >>>> A continuation of the "Why does the 115V->24V transformer keep blowing
> >>>> on my Trane XB80?" discussion I started on 04/02/2011.
>
> >> ...
>
> >>> ... Buy one of hevier one(bigger size and really heavier in
> >>> weight than stock) If it blows again, something on the load side is wrong.
>
> >> I'd venture something is already wrong...
>
> >> --
>
> > I'd agree. Responding to his first post and before he put this
> > latest transformer in I recommended measuring
> > how many amps are being drawn on the low voltage side.
> > This is electricity 101. So, he comes here asking for advice
> > and instead of listening, he justs puts another transformer in
> > and blows it too..... Go figure. Time to either get educated
> > or hire a pro.
>
> In case you hadn't noticed, I've been getting LOTS of (much appreciated) advice
> from many people, but it's also been very contradictory with no single
> suggested approach. It's been an interesting and informative discussion, and
> I've been happy that nobody's been a jerk about it... until *now*.
OK, so now I'm a jerk for suggesting that you should have taken some
basic
measurements, starting with the transformer output current, instead of
just
continuing to replace transformers and watch them blow. A
component that supplies power fails by burning up. You've replaced
it
several times now. You think just MAYBE it's a good idea to see how
much power it's be asked to supply instead of just buyng new
transformers?
If a fuse blew out, would you just keep putting in new fuses or would
you
measure the current and see what it is? I'd have measured the
voltages
and currents on both sides of the transformer after the first one
failed.
> And I DID
> listen; plenty of people suggested that the original transformer was likely to
> be under-rated and to replace it with something more heavy-duty.
I find it hard to believe that Trane uses transformers in it's
furnaces that are
so under-rated that they burn out in a day. I also question the
soundness of
anyone telling you to start installing transformers capable of
delivering more
power without even taking some basic measurements and finding out
what's
drawing current and if it's excessive for some reason. If you had a
light
circuit that was blowing fuses, would your approach be to put in a
bigger fuse
or would it be to find out what's really going on? If you have a
short somewhere
and you put in a large enough transformer, you think you might
eventually heat
something up enough to start a fire, like maybe in the thermostat
wiring in
your walls?
> Also, it
> seems to me that having a working transformer is a pre-requisite to following
> your advice of measuring the amp draw on the low voltage side, no?
> Unfortunately, time constraints prevented me from being there to perform those
> measurements when the unit was running, and unfortunately again the transformer
> blew in my absence.
So, you had the time to obtain a new transformer, put it in, but
didn't have the
1 minute it would take to use a VOM to measure the current and voltage
on
the secondary? If it were me and I saw transformers burning up, I
wouldn't
leave it on until I had some confidence as to what was going on.
>But of course, I'm repeating myself
Yes, by putting in each new transformer and watching it fail.
Tony Miklos
What were the specs of the original transformer?
Tony Miklos
Yes, it's called an open neutral. Can be quite dangerous.
Tony Miklos
It doesn't take any 220 (240) circuits to cause that.
Stormin Mormon
and the pole, and the power feeds in from the other leg?
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"Tony Miklos" <Tony....@gmail.com> wrote in message
news:90b5ha...@mid.individual.net...
Stormin Mormon
fellows on alt hvac are often heard to say "replace the
thermostat".
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
<tra...@optonline.net> wrote in message
news:5263130f-1529-4a40...@1g2000yqq.googlegroups.com...
Stormin Mormon
quite skilled enough to find it.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
<tra...@optonline.net> wrote in message
news:5f753403-c7ec-41a2...@x3g2000yqj.googlegroups.com...
Stormin Mormon
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"Steve Turner" <bbqb...@swtacobell.net.invalid>
wrote in message news:inpvh1$dq$1...@dont-email.me...
Jeff Thies
> 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):
It would seem to me that you are going to have to get yet another
transformer. Put a fuse on the primary, 1/2 A I would think. Slow blow,
perhaps less.
Then I'd check a couple things.
Note where it says that the integrated controller is polarity
sensitive. Check to make sure it is correct.
Then I would look to see if anything looks overheated on the
integrated controller.
I doubt it is any of the motors as those probably all run on line
voltage.
Jeff
>
>
> http://www.trane.com/webcache/un/furnaces%20%28furn%29/product/22-1666-07_04012009.pdf
>
>
Steve Turner
I said no such thing. Your advice is perfectly sound, but your suggestions
were just some of many, and you seem to think I didn't follow *yours* (not
true), and yes you were kind of a jerk in the way you voiced it. It wasn't
really necessary, was it? You apparently don't have the patience to read
everything I wrote, otherwise you wouldn't claim that I'm just "replacing
transformers and watching them blow".
> A component that supplies power fails by burning up. You've replaced
> it
> several times now. You think just MAYBE it's a good idea to see how
> much power it's be asked to supply instead of just buyng new
> transformers?
More evidence that you've chosen not to read everything that was written.
> If a fuse blew out, would you just keep putting in new fuses
I'm not an idiot. Not completely, anyway.
> or would you
> measure the current and see what it is? I'd have measured the
> voltages
> and currents on both sides of the transformer after the first one
> failed.
I know how to measure voltages (and I did; I mentioned that already) and
resistance to test for open circuits (continuity - See? I know some of the
terms. I even know the difference between A/C and D/C). But measuring and
understanding the ramifications of current (amperage) is where I get a little
fuzzy. Would you help me out? That's why I came here.
>> And I DID
>> listen; plenty of people suggested that the original transformer was likely to
>> be under-rated and to replace it with something more heavy-duty.
>
> I find it hard to believe that Trane uses transformers in it's
> furnaces that are
> so under-rated that they burn out in a day. I also question the
> soundness of
> anyone telling you to start installing transformers capable of
> delivering more
> power without even taking some basic measurements and finding out
> what's
> drawing current and if it's excessive for some reason. If you had a
> light
> circuit that was blowing fuses, would your approach be to put in a
> bigger fuse
> or would it be to find out what's really going on? If you have a
> short somewhere
> and you put in a large enough transformer, you think you might
> eventually heat
> something up enough to start a fire, like maybe in the thermostat
> wiring in
> your walls?
I agree completely. I had my reservations about following such advice (and I
only went a *little* higher on the replacements; far less than what some
suggested), but I'm not an expert and many people were singing the same song:
"Discount the first failure, things simply get old and fail"
"The second failure could likely just be an inferior replacement part."
Clearly the third failure proves those two theories false. Live and learn.
>> Also, it
>> seems to me that having a working transformer is a pre-requisite to following
>> your advice of measuring the amp draw on the low voltage side, no?
>> Unfortunately, time constraints prevented me from being there to perform those
>> measurements when the unit was running, and unfortunately again the transformer
>> blew in my absence.
>
> So, you had the time to obtain a new transformer, put it in, but
> didn't have the
> 1 minute it would take to use a VOM to measure the current and voltage
> on
> the secondary? If it were me and I saw transformers burning up, I
> wouldn't
> leave it on until I had some confidence as to what was going on.
I already explained what happened. I'm sorry you feel the ongoing need to
point out the stupidity of my approach. It is what it is. <Shrug>
> >But of course, I'm repeating myself
>
> Yes, by putting in each new transformer and watching it fail.
By golly, I think I'll do that again, it was such great fun.
Smarty
> A continuation of the "Why does the 115V->24V transformer keep blowing
> on my Trane XB80?" discussion I started on 04/02/2011.
>
> 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):
>
>
>
>
> 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.
>
> 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?
Steve,
If you are not comfortable with taking current measurements, or do not
have an ammeter, or do not wish to sit there waiting for some unusual
condition which is drawing too much current, you could temporarily
install an in-line fuse holder and automotive cartridge fuse rated at or
above the secondary side amperage which the transformer is rated. With
this fuse installed on the secondary side, in series with the load, you
could then determine if the load is indeed drawing too much current from
the secondary and burning out the transformer, versus primary side
excess voltage being the problem.
A rough guess would be that the contactor coil should maybe be drawing
about a quarter to a half an amp of current at 24V. The transformer
secondary should not need to source a lot more than that amount of
current to provide adequate power to the coil of the contactor.
Fuses are a lot cheaper than transformers......
There may be an intermittent short in the wiring to the coil, a short in
the coil itself, a breakdown of the coil insulation allowing a short to
ground when the coil heats up or cools or vibrates, etc.
Smarty
Steve Turner
> On Sat, 09 Apr 2011 14:41:05 -0500, Steve Turner wrote:
>
>> But measuring and
>> understanding the ramifications of current (amperage) is where I get a
>> little fuzzy. Would you help me out? That's why I came here.
>
> and convert that to the specs (volt-amps) of the transformer. If the draw
> is out of bounds of the specs then the 24 volt circuit is the problem.
> You can't put a band-aid on a bullet wound.
Yes, you did, and thanks for the suggestion. I've never used my meter to
measure amperage before, and I don't know how to do that conversion, but I will
study up on it.
The Daring Dufas
I think someone already mentioned the possibility of a bad neutral
connection allowing the supply voltage to shoot up.
TDD
Steve Turner
Yes Smarty, I would very much like to try this approach because I don't want to
zap any more transformers. Lots of people have suggested it, but there appear
to be more types of fuses than there are insects, and I have no idea what
*exact* type to look for. That's why I asked earlier in this thread if this
particular transformer:
with a built-in manual reset would be a much cleaner solution that serves the
same purpose, but I got no responses.
The specs on the original transformer were: Class 2, 115V primary (60hz), 24V
(35VA) secondary. Any chance you could point me to some _exact_ fuse solutions
for this application? There's a virtual six-pack of beer in it for you. :-)
David Nebenzahl
It's not a "conversion".
To measure current (which, properly speaking, is what you're measuring,
not "amperage"), you have to break the circuit and put the ammeter in
series with the circuit, so that all the current goes through the meter.
(As opposed to measuring voltage, where you put the meter *across*, or
in parallel with, the thing whose voltage you want to know.)
In your case, since you want to see how much current is being drawn from
the transformer, you'd put the ammeter between one of the transformer
secondary leads (doesn't matter which one) and whatever wire from your
unit that's supposed to connect to that lead.
Since you're measuring AC current, you'll need an AC ammeter, which
rules out most digital multimeters, which only are designed to measure
DC current. Not sure where you'd (quickly, easily) get an AC meter.
Maybe others can suggest? But that's how you do it.
--
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*?)
cl...@snyder.on.ca
The blower motor is NOT running on the 24 volt transformer, so will
have NO effect on the transformer.
You NEED to fuse the secondary - then IF it is an overload problem you
will just pop the fuse, and not the transformer. 24 volt, 35 VA = 1,5
amp FAST BLOW fuse.
If the fuse does not blow and the transformer does, it PROVES, almost
beyond a doubt, that you have bad luck getting a good transformer.
The other option is to closely monitor the primary current and see
what you have.
David Nebenzahl
>> If you are not comfortable with taking current measurements, or do not have an
>> ammeter, or do not wish to sit there waiting for some unusual condition which
>> is drawing too much current, you could temporarily install an in-line fuse
>> holder and automotive cartridge fuse rated at or above the secondary side
>> amperage which the transformer is rated. With this fuse installed on the
>> secondary side, in series with the load, you could then determine if the load
>> is indeed drawing too much current from the secondary and burning out the
>> transformer, versus primary side excess voltage being the problem.
>>
>> A rough guess would be that the contactor coil should maybe be drawing about a
>> quarter to a half an amp of current at 24V. The transformer secondary should
>> not need to source a lot more than that amount of current to provide adequate
>> power to the coil of the contactor.
>>
>> Fuses are a lot cheaper than transformers......
>>
>> There may be an intermittent short in the wiring to the coil, a short in the
>> coil itself, a breakdown of the coil insulation allowing a short to ground when
>> the coil heats up or cools or vibrates, etc.
>
> Yes Smarty, I would very much like to try this approach because I don't want to
> zap any more transformers. Lots of people have suggested it, but there appear
> to be more types of fuses than there are insects, and I have no idea what
> *exact* type to look for.
Well, it's not exactly rocket science. And you can't hurt anything,
unless you get a fuse that's too big (i.e., rated at too many amps).
First thing you gotta figure out is how much current your transformer is
rated at. Since your wiring diagrams don't say, we have to take an
educated guess.
The only thing connected to the transformer is a thingamajig called the
"integrated furnace control" (IFC). Even without seeing this thing, I
can guess with confidence that it's an electronic circuit board which
controls the operation of the furnace. Since it undoubtedly does so
through relays (either mechanical or electronic), it's safe to assume
that it doesn't draw much current.
Let's say 1 amp to start. We could be wrong, but that's a good starting
point. So what we need is a fuse rated at *at least* 24 volts (could be
much more, up to 120 or 240 volts), and *exactly* 1 amp. To be on the
safe side, let's get a "fast blow" fuse. Hey, fuses are cheaper than
transformers, right?
So install such a fuse, run the unit and see what happens.
If the fuse blows right away, it's probably too small, so use the next
bigger fuse; let's say 1.5 A.
Now you want to stop at some point, let's say 2-3 amps, because now
you're getting up to where you may be exposing whatever fault there is
with the unit and risking blowing the transformer again. If this
happens, you're going to have to bite the bullet and find out what's
wrong with the damn thing. But at least your 3rd transformer will still
be intact.
cl...@snyder.on.ca
<billnoma...@yahoo.com> wrote:
>"Steve Turner" <bbqb...@swtacobell.net.invalid> wrote in message
>news:inomp2$vc8$1...@dont-email.me...
>> On 4/8/2011 10:16 PM, Tony Miklos wrote:
>>> On 4/8/2011 8:52 PM, Steve Turner wrote:
>>>> 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).
>>>
>>> Three times it fried the primary? I'd guess it's getting 240vac at
>>> times. It's
>>> very unusual for the primary to go bad from a short on the
>>> secondary side, and
>>> the picture shows that the secondary wasn't overheated like the
>>> primary was.
>>> Where's all those electricians talking about an open neutrals when
>>> you need
>>> them? If it measures 120vac tie a light bulb into the primary side
>>> and leave it
>>> where it can be seen. Have the family let you know if it ever gets
>>> brighter
>>> than normal. Or better yet, call a pro.
>>
>> That very thought crossed my mind, but I'm not sure how that could
>> happen. The unit is on a dedicated 115V circuit tied to a
>> single-pole breaker. Where would the possibility exist for the
>> neutral to become hot? In the breaker box?
>>
>
>A neutral in a breaker box could have a loose connection. These
>connections can heat up and cool down as more/less electricity is used
>on the panel in question. And there may be a point where the
>connection fails momentarily or arcs. Then if you lose the neutral
>connection, 120 volt circuits become 240 volt circuits via other
>circuits turned on in the panel on the other leg.
>
>The solution to that problem is usually to have the electric company
>or electrician retorque the main panel lug nuts to the panel
>manufacturers tightness specifications in inch lbs. Note POWER IS
>ALWAYS HOT TO THESE CONNECTIONS and this is NOT a DIY thing!
>
>A similar problem can be with what is called a MWBC or Multi-Wire
>Branch Circuit. These are 2 separate 120 V circuits run to the same
>area that share one neutral wire. So 2 hots and 1 neutral coming from
>the breaker panel. A loose neutral connection with that one wire and
>same problem.
MWBC is not legal for a furnace and never has been (at least in
Canada) and a main panel neutral problem should have manifested
iteself with light bulbs flaring/dimming or other indications of
"wonky" voltage elsewhere in the house.
>
>When the entire panel is having this problem, you would see lights get
>brighter as the problem occurs.
>
>If just a problem with one MWBC, then only those circuits would have
>the problem.
David Nebenzahl
> An amp meter goes in series with the secondary (or primary) of the
> transformer. You can convert amps to volt-amps by multiplying volts times
> amps. 24 volts times 1 amp = 24 volt-amps. I don't remember if
> transformers are rated differently for the primary or secondary or which
> one is usually used. It might be in the technical data usually packed
> with the transformer or stamped on the transformer somewhere.
Using the primary side would be more conservative (= a bit safer), since
it will include any losses between primary and secondary sides. But it
really doesn't matter. And I'd much prefer to measure current on the
secondary side, rather than deal with 120-volt juice.
He still has the problem of finding an AC ammeter, since a DMM won't
handle AC current.
David Nebenzahl
> Agree, sounds like electrical problem, and the OP isn't
> quite skilled enough to find it.
... and you're certainly not competent to even comment on it.
Stormin Mormon
the transformer BLOWS, it might still be a BAD NEUTRAL. At
this point, MY best GUESS is some kind of problem with the
SECONDARY wiring. But, I'm NOT THERE to check.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
<cl...@snyder.on.ca> wrote in message
news:9pj1q65pr51gn6fku...@4ax.com...
On Fri, 08 Apr 2011 19:52:06 -0500, Steve Turner
You NEED to fuse the secondary - then IF it is an overload
David Nebenzahl
I agree. Suggesting that the OP's problem is due to a buggy Edison
circuit (and why don't they just call them that, since that's what
everyone else calls 'em?) is just grasping at straws. Possible, sure,
but highly unlikely.
Stormin Mormon
S'appenin
In earlier post, he said it's 24 VAC, 35 VA.
Tnx
Ywlcm
by
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4da0d153$0$13264$8226...@news.adtechcomputers.com...
The Daring Dufas
> On 4/9/2011 10:59 AM, The Daring Dufas wrote:
>> On 4/9/2011 10:48 AM, Steve Turner wrote:
>>> On 4/9/2011 9:12 AM, tra...@optonline.net wrote:
>>>> On Apr 8, 10:05 pm, dpb<n...@non.net> wrote:
>>>>> On 4/8/2011 8:44 PM, Tony Hwang wrote:
>>>>>
>>>>>>> A continuation of the "Why does the 115V->24V transformer keep
>>>>>>> blowing
>>>>>>> on my Trane XB80?" discussion I started on 04/02/2011.
>>>>>
>>>>>
>>>>>> ... Buy one of hevier one(bigger size and really heavier in
>>>>>> weight than stock) If it blows again, something on the load side is
>>>>>> wrong.
>>>>>
>>>>> I'd venture something is already wrong...
>>>>>
>>>>> --
>>>>
>>>> I'd agree. Responding to his first post and before he put this
>>>> latest transformer in I recommended measuring
>>>> how many amps are being drawn on the low voltage side.
>>>> This is electricity 101. So, he comes here asking for advice
>>>> and instead of listening, he justs puts another transformer in
>>>> and blows it too..... Go figure. Time to either get educated
>>>> or hire a pro.
>>>
>>> In case you hadn't noticed, I've been getting LOTS of (much appreciated)
>>> advice from many people, but it's also been very contradictory with no
>>> single suggested approach. It's been an interesting and informative
>>> discussion, and I've been happy that nobody's been a jerk about it...
>>> original transformer was likely to be under-rated and to replace it with
>>> transformer is a pre-requisite to following your advice of measuring the
>>> amp draw on the low voltage side, no? Unfortunately, time constraints
>>> prevented me from being there to perform those measurements when the
>>> unit was running, and unfortunately again the transformer blew in my
>>>
>>
>> Steve I really hope you can figure out the problem with the furnace and
>> I can understand the bit about time constraints. Installing a fuse in
>> series
>> with with either side of the transformer is cheap insurance to
>> keep from losing another transformer. The fuse holders are inexpensive
>> and it's a lot less of a hassle to replace a blown fuse.
>>
>> TDD
>
> Yes, I would be more than willing to do that, but my electricity
> training is not quite up to the 101 level that trader4 seems to think I
> should have; can you suggest a specific fuse rating that I should use?
> Thanks!
>
Most control boards have a place to plug in a low voltage blade fuse
just like the ones introduced to automobiles by GM years ago. The value
will vary from 3 to 5 amps. A one amp fuse should be sufficient for the
primary/120volt side. The primary fuse should be installed in series
with the black/hot wire of the transformer and the low voltage fuse
should be installed in series with the red/R wire OOPS! I just noticed
something from the pictures of the burned transformer! The wire colors
in the control system of air handler/furnace wiring can vary a little
from manufacturer to manufacturer and I just saw something that may be
a problem causing confusion. The transformer in the picture has a YELLOW
wire in place of the RED low voltage output. The black/hot and
white/neutral are for the 120vac connection and the yellow/R and blue/C
are on the other side of the transformer. The red and orange wires
should be taped up because they are for 208-240 volt connections. If the
red wire on that transformer were hooked to the red wire connections
shown in the wiring diagram, it will burn up. Yellow is usually the low
voltage wire color used for safety switches, pressure switches and
interlocks. The blue wire is the common 24vac and is often grounded to
the metal cabinet of the furnace. A seasoned HVAC tech would have seen
the anomaly immediately and it wouldn't have posed a problem.
TDD
TDD
cl...@snyder.on.ca
1.5 amp fast blow for the secondary, no more than 500ma for the
primary if the original was 35va. full rated load would be about .3
amps, so a 250ma would be boarderline. (but the transformer should NOT
be running full rated load, either)
Take the va rating and devide by the voltage to get the current rating
in amps. 40va at 24 volts= 1.66 amps. 40va at 115 volts = .347 amps.
40 va at 127 volts = 0.315, etc.
Stormin Mormon
Home!
Hangin, slick?
http://www.harborfreight.com/digital-clamp-meter-96308.html
Good enough for government work!
dude.
This one only goes up to 200 mA, needs higher range than
that.
http://www.harborfreight.com/ac-dc-digital-multimeter-37772.html
Bummer.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4da0d29a$0$13264$8226...@news.adtechcomputers.com...
David Nebenzahl
> The specs on the original transformer were: Class 2, 115V primary (60hz), 24V
> (35VA) secondary. Any chance you could point me to some _exact_ fuse solutions
> for this application? There's a virtual six-pack of beer in it for you. :-)
Guess I missed that.
35 VA/24 V = 1.45A, so you need a 1.5A fuse. Fast-blow.
Get the kind that'll fit in an in-line fuse holder (the little glass
jobbies with metal contacts on the ends). Should be available even at
Radio Shack.
Stormin Mormon
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4da0d37c$0$13264$8226...@news.adtechcomputers.com...
The Daring Dufas
> Agree, sounds like electrical problem, and the OP isn't
> quite skilled enough to find it.
>
I just saw it in the picture and posted what the problem is.
I would have seen it immediately if I was hands on. Look at
the wire colors on the transformer especially the YELLOW, it
is taking the place of the RED wire for low voltage. Notice the
yellow and blue are on one side of the transformer. I don't know
why I didn't notice it before. ^_^
TDD
Steve Turner
Not to worry; I read the directions. The red and orange wires were indeed
taped up and not used; only the white and black wires on the input side were
hooked up in the normal fashion. The blue and yellow wires on the 24V output
side of the transformer were hooked to the blue and red wires (respectively)
leading to the control board. I measured input and output voltages after
installing the transformer, and I ensured that I was getting 24V on the output
side before I hooked those leads to the control board. The control board then
came up with it the flashing red LED to indicate normal ("no call for heat")
operation.
The Daring Dufas
Well, that blew that theory! ^_^
TDD
David Nebenzahl
> You do make mistakes, now and again. This is one, such.
No.
I make mistakes. You're an ignoramus.
See the difference?
Steve Turner
Interesting; thank you. My meter is an Extech MN26T:
http://www.extech.com/instruments/resources/manuals/MN26_UM.pdf
According to the operating instructions, my meter supports "AC or DC Current
Measurement"
Steve Turner
Great information David. Thanks!
David Nebenzahl
Yep. You've got a better meter than I, and it's up to this task. Just
connect it as I described (be sure to use the correct connectors on the
meter, the ones marked "10A" and "COM"), make sure it's on the highest
current range (10A), and you're good to go.
Jeff Thies
It's not that hard, or that critical.
Put this on the primary:
http://www.radioshack.com/product/index.jsp?productId=2103752
.25A
This on the secondary:
http://www.radioshack.com/product/index.jsp?productId=2102740&numProdsPerPage=60
1.5A
You can put them in this:
http://www.radioshack.com/product/index.jsp?productId=2102782&numProdsPerPage=60
But first do as I suggested in another thread,look carefully for
anything burnt and check the polarity of the line. Make sure the neutral
is neutral. You can measure from the ground prong. See the note in the
schematic. I'm not so sure this didn't arc to the transformer shell,
from looking at the pic. You may wish to measure voltage (AC) from the
transformer shell to a guaranteed neutral.
It is OK for the transformer to run a little warm, it shouldn't be hot.
There are two kinds of failures, one is a long term thermal failure
(which seemed likely when you said years had gone by), the other is a
transient short, or maybe not so transient. If that is the case then
something else will be bad. It may look burnt, or if it is a diode or
transistor it may just be shorted. You can Google how to test those.
Don't be afraid to put a quick finger on a transistor to see if it is
hot, or on the transformer.
As far as calculating what size fuse, you should know Ohms law. Current
* voltage is watts, or in this case V(olt)A(mps). 120V * 1/4A = 30 VA,
on the out side, 24V * 1.5 = 36 VA.
Note that there is a small surge when you turn on a device. So it may
peak higher at the instant of turning on. A fuse usually can absorb
that. The white ceramics are faster blowing and the slow blow ones
usually have a little coil inside the fuse to show it down and are
marked slow blow. When/if you fix this, leave in the fuses and we can
give you some guidance on more properly sizing them. But some fuse in
the ballpark is definitely better than nothing.
Jeff
Smitty Two
Hello? tap tap tap. Is this thing on? I mentioned that yesterday, duf.
Or maybe this morning. Time gets distorted on weekends.
robb
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
Jim Yanik
news:WfKdnQOvu_d2bz3Q...@earthlink.com:
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?
--
Jim Yanik
jyanik
at
localnet
dot com
cl...@snyder.on.ca
>Since you're measuring AC current, you'll need an AC ammeter, which
>rules out most digital multimeters, which only are designed to measure
>DC current. Not sure where you'd (quickly, easily) get an AC meter.
>Maybe others can suggest? But that's how you do it.
Pardon? every one of my digital meters has an ac current range.. The
one on my desk right now has a 200ma and a 20 amp scale, while for DC
it has 2ma,20ma, 200ma, and 20 amp.
My "pocket" meter has 2 amp and 10 amp AC and dc
My "bench" meter has 300ma and 10 amp, both AC and DC.
The first digital meter I ever owned (and I still have it) has 2ma,
200ma and 10 amp ranges (and it is 30 years old)
And my"amp clamp" reads 200 or 1000 amps
cl...@snyder.on.ca
wrote:
>On Sat, 09 Apr 2011 16:04:32 -0500, Steve Turner wrote:
>
>> On 4/9/2011 2:58 PM, A. Baum wrote:
>>> On Sat, 09 Apr 2011 14:41:05 -0500, Steve Turner wrote:
>>>
>>>> But measuring and
>>>> understanding the ramifications of current (amperage) is where I get a
>>>> little fuzzy. Would you help me out? That's why I came here.
>>>
>>> I advised you the last time to measure the 24 volt circuit amperage
>>> draw and convert that to the specs (volt-amps) of the transformer. If
>>> the draw is out of bounds of the specs then the 24 volt circuit is the
>>> problem. You can't put a band-aid on a bullet wound.
>>
>> Yes, you did, and thanks for the suggestion. I've never used my meter
>> to measure amperage before, and I don't know how to do that conversion,
>> but I will study up on it.
>
>An amp meter goes in series with the secondary (or primary) of the
>transformer. You can convert amps to volt-amps by multiplying volts times
>amps. 24 volts times 1 amp = 24 volt-amps. I don't remember if
>transformers are rated differently for the primary or secondary or which
>one is usually used. It might be in the technical data usually packed
>with the transformer or stamped on the transformer somewhere.
>
>If the spec is for the primary then it would be 117 x amps. Of course the
>measurements should be taken while the unit is in heat mode.
The rating is "output" which means the secondary. Primary power will
always be slightly higher due to efficiency issues.
cl...@snyder.on.ca
We don't need to guess here.
The transformer has a rating. NEVER fuse above the transformer rating.
If the transformer is a 40va 24 volt transformer the MAXIMUM fuse
rating is 40/24=1.66 amps - so a 1.5 amp fuse will protect the
transformer - a 2 amp fuse will NOT.
cl...@snyder.on.ca
<nob...@but.us.chickens> wrote:
>On 4/9/2011 2:30 PM A. Baum spake thus:
>
>> An amp meter goes in series with the secondary (or primary) of the
>> transformer. You can convert amps to volt-amps by multiplying volts times
>> amps. 24 volts times 1 amp = 24 volt-amps. I don't remember if
>> transformers are rated differently for the primary or secondary or which
>> one is usually used. It might be in the technical data usually packed
>> with the transformer or stamped on the transformer somewhere.
>
>Using the primary side would be more conservative (= a bit safer), since
>it will include any losses between primary and secondary sides. But it
>really doesn't matter. And I'd much prefer to measure current on the
>secondary side, rather than deal with 120-volt juice.
>
>He still has the problem of finding an AC ammeter, since a DMM won't
>handle AC current.
As noted previously, this is NOT the case. An AUTOMOTIVE DMM might not
have an AC current scale, but virtually all general purpose meters do.
They generally have a "third terminal" used with the common for the
high range, which will be what he wants to use since the low range
that uses the standard (vom) connections generally tops out at 300ma,
more or less.
cl...@snyder.on.ca
<cayoung61**spamblock##@hotmail.com> wrote:
>Well, the way I see it. If he FUSES the SECONDARY side, and
>the transformer BLOWS, it might still be a BAD NEUTRAL. At
>this point, MY best GUESS is some kind of problem with the
>SECONDARY wiring. But, I'm NOT THERE to check.
He needs to fuse the secondary and meter the primary, and have someone
switch all the loads while he watches the meter. This will tell if he
has a neutral issue, because a load on the "other phase" will cause
the voltage to go up while a load on the "same phase" will cause the
voltage to go down.
Even simpler, when the blower motor comes on, if he has a neutral
issue the voltage on the primary WILL DROP. Absolutely no question.
(and more than 1 volt - virtually guaranteed)
David Nebenzahl
Well, all I can say is that *none* of my 3 general-purpose multimeters
(2 analog and 1 DMM) have AC current settings. But apparently this is a
non-issue in this case, as the OP's meter definitely has AC current
capability.
cl...@snyder.on.ca
You are sure that's the problem??
There are NO STANDARDS when it comes to transformer wiring colours
(outside of the radio/communications industry, and even there, the
beauty of standards is there are so many to choose from)
He needs to go by the wiring diagram that came with the transformer,
and VERIFY IT WITH A VOLTMETER.
David Nebenzahl
> On Sat, 09 Apr 2011 16:57:57 -0500, The Daring Dufas
> <the-dari...@stinky.net> wrote:
>
>> On 4/9/2011 1:13 PM, Stormin Mormon wrote:
>>
>>> Agree, sounds like electrical problem, and the OP isn't quite
>>> skilled enough to find it.
>>
>> I just saw it in the picture and posted what the problem is. I
>> would have seen it immediately if I was hands on. Look at the wire
>> colors on the transformer especially the YELLOW, it is taking the
>> place of the RED wire for low voltage. Notice the yellow and blue
>> are on one side of the transformer. I don't know why I didn't
>> notice it before. ^_^
>
> You are sure that's the problem??
> There are NO STANDARDS when it comes to transformer wiring colours
> (outside of the radio/communications industry, and even there, the
> beauty of standards is there are so many to choose from)
Ain't that the truth!
> He needs to go by the wiring diagram that came with the transformer,
> and VERIFY IT WITH A VOLTMETER.
Which he has already done, if you'd bothered to read all his postings.
cl...@snyder.on.ca
<bbqb...@swtacobell.net.invalid> wrote:
>http://www.extech.com/instruments/resources/manuals/MN26_UM.pdf
The instrument is definitely capable. Use the 10 amp scale, with the
leads in the common and 10a jacks.
cl...@snyder.on.ca
wrote:
>
> But first do as I suggested in another thread,look carefully for
>anything burnt and check the polarity of the line. Make sure the neutral
>is neutral. You can measure from the ground prong. See the note in the
>schematic. I'm not so sure this didn't arc to the transformer shell,
>from looking at the pic. You may wish to measure voltage (AC) from the
>transformer shell to a guaranteed neutral.
It's AC so there is no polarity. It's single output, non grounded, so
it doesnt matter which direction either the primary or secondary are
connected. Good to have the white on neutral and the bloack on live,
but it will have NO EFFECT on the operation. - or the life of the
transformer.
cl...@snyder.on.ca
wrote:
Or just another crappy transformer.
You do not just ASSume it is the transformer
>>>
>>
>> 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?
Transient overvoltages of less than 20% or there-abouts are unlikely
to blow the transformer primary of the furnace without manifesting
themselves elsewhere in the house - and over 20% would definitely
manifest themselves elsewhere.
Steve Turner
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.
The Daring Dufas
Steve wrote that the instructions pointed it out so another theory out
the window. Looks like it may be a intermittent floating neutral after
all. Oh tap, tap, tap, I don't think I've read all the posts so I may
have missed your brilliant deduction. I started reading the thread when
I noticed how long it was getting and no one was blaming BeeHO for it.
ROTFL
TDD
John Robertson
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 :-#)#
--
(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."
The Daring Dufas
No it's not, Steve wrote that the included instructions pointed out the
difference in wire color. I may have to change a compressor tomorrow so
I'm sure I'll see all kind of colors when I get a whiff of phosgene gas
when I hit the lines with my torch. ^_^
TDD
Phil Allison
"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
Congoleum Breckenridge
> In article<inoplc$bhu$1...@dont-email.me>,
> Steve Turner<bbqb...@swtacobell.net.invalid> wrote:
>
> <snip>
>
> You might start at the beginning and make sure everything is hooked up
> correctly. I mean, once you spring for yet another transformer. For
> example, your latest fried transformer has six wires. The schematic
> shows the secondary wire colors as blue and red. Given the location of
> the blue and red wires on the pic of the transformer you have, that's
> not quite intuitive.
>
> And, it may not even be right. So I'd buy a new one, and check some
> voltages on the bench. Put 120 into the black and white, and then
> measure every other pair to make sure you understand which two wires are
> really putting out 24 V.
>
> Obviously, when you go to install it, clip and shrink tube the unused
> wires, and make sure that leads are dressed so that they won't short
> anywhere.
>
> Then I'd be monitoring the damn thing, preferably with a voltmeter
> perhaps on the primary and an ammeter on the secondary.
That 3rd transformer looks like a dual voltage (120/240) input.
If it is, it has two primary windings, and both need to be wire up to work.
Like this: http://www.eleinmec.com/figures/027_02.gif
Mark
> On 4/9/2011 1:37 AM, Smitty Two wrote:
>
>
>
> > Steve Turner<bbqbo...@swtacobell.net.invalid> wrote:
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.
If there is some insulation problem on the ignition wires and the VERY
high voltage from the ignition circuit is sparking or jumping over to
the transformer primary circuit, this could cause the symptoms you are
seeing.
Make sure the wires that are part of the ignition circuit are not even
close to the anything else. and inspect them (with the power off) for
any sigh of cracks or other faults. These have very high voltage
like in a car spark plug and can jump several inches if there is an
insulation problem. And the problem would be intermittent. The
transformer primary voltage would look perfect except when the high
voltage spark jumps over to it and this could easily damage the
insulation on the transformer which is not designed for very high
voltages.
If you are an electrical novice, you may want to think about calling
in for some help at this point.
Mark
Jeff Thies
> On Sat, 09 Apr 2011 19:22:57 -0400, Jeff Thies<jeff_...@att.net>
> wrote:
>
>
>>
>> But first do as I suggested in another thread,look carefully for
>> anything burnt and check the polarity of the line. Make sure the neutral
>> is neutral. You can measure from the ground prong. See the note in the
>> schematic. I'm not so sure this didn't arc to the transformer shell,
>>from looking at the pic. You may wish to measure voltage (AC) from the
>> transformer shell to a guaranteed neutral.
>
> It's AC so there is no polarity. It's single output, non grounded, so
> it doesnt matter which direction either the primary or secondary are
> connected. Good to have the white on neutral and the bloack on live,
> but it will have NO EFFECT on the operation. - or the life of the
> transformer.
Except that the schematic has a note at the top that says:
Important
Integrated Control is polarity sensitive.
Hot leg of 120V power supply must be connected to the black power lead...
Whats with that?
Otherwise I would fully agree with you.
It seems to me there is a flaw in the integrated control and whereas
I don't see how this could be a problem, it is easy enough to scratch
off the list. Troubleshooting is little more than eliminating possibilities.
Jeff
Phil Allison
"Phil Allison"
> firstly an in-line fuse of say 1/4 amp ....
** Must be a "slo-blo" type fuse.
.... Phil
Stormin Mormon
comptetent to answer this question. At work, I regularly
measure amperage without splicing into the circuit. You
should stick to things you know.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4da0cf4a$0$5306$8226...@news.adtechcomputers.com...
Stormin Mormon
closely. I hope your trip charge isn't too much, in this
case?
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"The Daring Dufas" <the-dari...@stinky.net>
wrote in message news:inqkp6$qad$1...@dont-email.me...
Stormin Mormon
would you be con-fused?
Still got an electrical problem to find.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"The Daring Dufas" <the-dari...@stinky.net>
wrote in message news:inqle3$127$2...@dont-email.me...
>
> Not to worry; I read the directions. The red and orange
> wires were
> indeed taped up and not used; only the white and black
> wires on the
> input side were hooked up in the normal fashion. The blue
> and yellow
> wires on the 24V output side of the transformer were
> hooked to the blue
> and red wires (respectively) leading to the control board.
> I measured
> input and output voltages after installing the
> transformer, and I
> ensured that I was getting 24V on the output side before I
> hooked those
> leads to the control board. The control board then came up
> with it the
> flashing red LED to indicate normal ("no call for heat")
> operation.
Well, that blew that theory! ^_^
TDD
Stormin Mormon
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4da0d948$0$13264$8226...@news.adtechcomputers.com...
On 4/9/2011 2:55 PM Stormin Mormon spake thus:
> You do make mistakes, now and again. This is one, such.
No.
I make mistakes. You're an ignoramus.
See the difference?
Stormin Mormon
that David's writings sound fancy, but he's not competent to
comment.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"Steve Turner" <bbqb...@swtacobell.net.invalid> wrote in
message news:inqm3r$an7$2...@dont-email.me...
On 4/9/2011 4:37 PM, David Nebenzahl wrote:
> So install such a fuse, run the unit and see what happens.
>
> If the fuse blows right away, it's probably too small, so
> use the next bigger
> fuse; let's say 1.5 A.
>
> Now you want to stop at some point, let's say 2-3 amps,
> because now you're
> getting up to where you may be exposing whatever fault
> there is with the unit
> and risking blowing the transformer again. If this
> happens, you're going to
> have to bite the bullet and find out what's wrong with the
> damn thing. But at
> least your 3rd transformer will still be intact.
Great information David. Thanks!
Stormin Mormon
meter. Not the David directions.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4da0e7f6$0$12850$8226...@news.adtechcomputers.com...
On 4/9/2011 3:11 PM Steve Turner spake thus:
>
> Interesting; thank you. My meter is an Extech MN26T:
>
> http://www.extech.com/instruments/resources/manuals/MN26_UM.pdf
>
> According to the operating instructions, my meter supports
> "AC or DC Current
> Measurement"
Yep. You've got a better meter than I, and it's up to this
task. Just
connect it as I described (be sure to use the correct
connectors on the
meter, the ones marked "10A" and "COM"), make sure it's on
the highest
current range (10A), and you're good to go.
Stormin Mormon
them that they are doing it wrong. They will thank you.
Don't take no for an answer.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
<cl...@snyder.on.ca>
wrote in message
news:8k02q61g9fs673orm...@4ax.com...
Smarty
> On 4/9/2011 3:43 PM, Smarty wrote:
>> On 4/8/2011 8:52 PM, Steve Turner wrote:
>>> blowing on my
>>> Trane XB80?" discussion I started on 04/02/2011.
>>>
>>> diagram) here:
>>>
>>> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>>>
>>> the wiring
>>> diagrams that I also copied to my above flickr site as jpg images):
>>>
>>>
>>>
>>>
>>>
>>> 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
>
> Yes Smarty, I would very much like to try this approach because I
> don't want to zap any more transformers. Lots of people have
> suggested it, but there appear to be more types of fuses than there
> why I asked earlier in this thread if this particular transformer:
>
> http://www.pexsupply.com/White-Rodgers-90-T60C3-Transformer-60VA-50-60-Hz-120-208-240V-Primary-24V-Secondary-Foot-Mount-14937000-p
>
>
> with a built-in manual reset would be a much cleaner solution that
> serves the same purpose, but I got no responses.
>
> The specs on the original transformer were: Class 2, 115V primary
> (60hz), 24V (35VA) secondary. Any chance you could point me to some
> _exact_ fuse solutions for this application? There's a virtual
> six-pack of beer in it for you. :-)
Here is the fuse holder, available at Radio Shack for a couple bucks:
http://www.radioshack.com/product/index.jsp?productId=2102784
Ask the Radio Shack clerk to sell you some compatible fuses which are
fast acting approx 1 or 1.5 amp size. If your transformer is 35VA rated,
it should be able to pump out an amp continuously without damage. A 1
amp fuse will allow it to provide 24 VA (24 volts X 1 amp) which is well
below the rating.
Your contactor should not draw anywhere near 24VA, and if it does, the
problem needs to be in either the contactor or the wiring to the contactor.
Good luck.
Jeff Thies
1 uF sounds a little high.
I would think .01 uF at 400V would be a better bet. Or an MOV (metal
oxide varistor) or three (across the line and then from each side to
ground).
I don't think this is a voltage spike problem though. Voltage spikes
take out other components first.
Jeff
>
>
>
> ..... Phil
>
>
>
>
>
>
>
tra...@optonline.net
> On 4/9/2011 9:41 PM, cl...@snyder.on.ca wrote:
>
>
>
>
>
> > wrote:
>
> >> But first do as I suggested in another thread,look carefully for
> >> anything burnt and check the polarity of the line. Make sure the neutral
> >> is neutral. You can measure from the ground prong. See the note in the
> >> schematic. I'm not so sure this didn't arc to the transformer shell,
> >>from looking at the pic. You may wish to measure voltage (AC) from the
> >> transformer shell to a guaranteed neutral.
>
> > It's AC so there is no polarity. It's single output, non grounded, so
> > it doesnt matter which direction either the primary or secondary are
> > connected. Good to have the white on neutral and the bloack on live,
> > but it will have NO EFFECT on the operation. - or the life of the
> > transformer.
>
> Except that the schematic has a note at the top that says:
>
> Important
> Integrated Control is polarity sensitive.
> Hot leg of 120V power supply must be connected to the black power lead...
>
> Whats with that?
I recently installed a Rheem and the installation manual clearly
stated
that the furnace would not start and would come up with a fault
condition if the hot and neutral were reversed. Don;t know exactly
how that one is wired or designed vs the Trane, but at least for
Rheem it does make a difference. But I suspect the main effect
is that the controller board detects it and just causes a fault. I
don't see how a reversed hot/neutral would be causing this guys
problem,
but it is one thing I would have checked long ago, or if I didn't
understand the basic steps, I would have called in a pro.
>
> Otherwise I would fully agree with you.
>
> It seems to me there is a flaw in the integrated control and whereas
> I don't see how this could be a problem, it is easy enough to scratch
> off the list. Troubleshooting is little more than eliminating possibilities.
>
> Jeff
>
>
>
> >> It is OK for the transformer to run a little warm, it shouldn't be hot.
>
> >> There are two kinds of failures, one is a long term thermal failure
> >> (which seemed likely when you said years had gone by), the other is a
> >> transient short, or maybe not so transient. If that is the case then
> >> something else will be bad. It may look burnt, or if it is a diode or
> >> transistor it may just be shorted. You can Google how to test those.
>
> >> Don't be afraid to put a quick finger on a transistor to see if it is
> >> hot, or on the transformer.
>
> >> As far as calculating what size fuse, you should know Ohms law. Current
> >> * voltage is watts, or in this case V(olt)A(mps). 120V * 1/4A = 30 VA,
> >> on the out side, 24V * 1.5 = 36 VA.
>
> >> Note that there is a small surge when you turn on a device. So it may
> >> peak higher at the instant of turning on. A fuse usually can absorb
> >> that. The white ceramics are faster blowing and the slow blow ones
> >> usually have a little coil inside the fuse to show it down and are
> >> marked slow blow. When/if you fix this, leave in the fuses and we can
> >> give you some guidance on more properly sizing them. But some fuse in
> >> the ballpark is definitely better than nothing.
>
> >> Jeff- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
tra...@optonline.net
> "robb" <s...@where.on.net> wrote innews:WfKdnQOvu_d2bz3Q...@earthlink.com:
>
>
>
>
>
> > "Steve Turner" wrote in messagenews:inoakf$qin$1...@dont-email.me...
>
> >> blowing on my Trane XB80?" discussion I started on 04/02/2011.
>
> >> diagram) here:
>
> >> http://www.flickr.com/photos/bbqboyee/sets/72157626457562742/
>
> >> 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
>
> >> of the 115V leads going into the transformer, and of course the 115V
> >> 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?
>
> powers the controller board and relays.
> either something is loading the transformer or a problem with input
> voltage.
>
>
It also could be powering a thermostat. Some of them will take power
from the transformer circuit. For example, I have a Honeywell
VisionPro
that has an optional 24V connection to power the thermostat, with
batteries then being the backup. Doing it that way allows the display
to be backlit 24/7 too.
Also, it's not unusual to have humdifiers tied into the 24V circuit
too.
Again, he needs to start doing some basic current measurements,
starting at the transformer and find out how much current the whole
thing is drawing and then if it's high, work to isolate it. If the
current
is normal, then I'd put in a 1.5 amp fuse in the secondary
temporarily.
Contrary to the suggestions to use a fast blow, I'd probably just use
a regular one, as whatever is capable of destroying a transformer
should be most capable of opening any fuse.
>
>
>
>
>
> > 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.
That's a good idea too.
>
> > 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.
I don't see how he could have a waveform that is so out of shape that
it
burns up this one specific transformer, yet there are no apparent
complaints of any other problems in the house. Or how you'd get
such a badly distorted waveform in the house in the first place.
> 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 -
Mark
David
>news:fe82a1bf-396e-4db1...@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.
>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
Mark
David,
I think you are right...
well it sounded good anyway....
regards
Mark
David Nebenzahl
> Steve, read and follow the directions that came with the
> meter. Not the David directions.
What, you're saying mine are wrong? Exactly how, pray tell?
You really are an idiot.