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  1. #14
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    4,923
    Quote Originally Posted by syndicated View Post
    A good inspection camera will help as well.
    My first journeyman told me a trick that I still use in tough cases. Pour water over the heat exchanger, if you can see inside the HX, the water will soak through.
    Goodman denies that method for warranty claims. :-\
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  2. #15
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    X 2 on rollouts


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  3. #16
    Join Date
    Nov 2009
    Location
    Northwest Illinois
    Posts
    275
    Quote Originally Posted by syndicated View Post
    Pour water over the heat exchanger, if you can see inside the HX, the water will soak through.
    You can't pour water on a serpentine style heat exchanger. Most stamped HX's seams will expand and tighten up after the burners are on. The water method really only works well with older welded HX's.

    To the OP, pull the blower out on 80% furnaces and crawl in with a mirror and flashlight and look at all of the eyelets/crimp rings, you'll be surprised at how many cracks you find. For 90% and above try going through the limit hole or from under the coil (it's a b@&!?) and look at the eyelets that way. Some models crack in different spots, the more you look at the more you will find.

  4. #17
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    You have gone way beyond a crack if roll outs are tripping, could be deep into split wide open territory depending on how the air from the blower hits the breach. Hell I've seen tube exchangers in rooftop units with rust holes so big you could stick two fingers in it and the roll out wasn't tripping and others did trip a roll out with an itty bitty pin hole in a welded seam. Had a goodman last year that had a crimp ring cracked in half. Cool it looked like a good ring but once it warmed up the halves seperated 3/8th an inch, no roll out issues. Duracurves cracked in every cell would be another prime example.

    Pretty sure getting into the specifics on testing heat exchangers on an open forum isn't allowed here. That's why I strongly suggest taking the class. The boss has sent 9 of us through and recouped the fees in a week or less.

  5. #18
    Join Date
    May 2011
    Posts
    54
    You have gone way beyond a crack if roll outs are tripping, could be deep into split wide open territory depending on how the air from the blower hits the breach. Hell I've seen tube exchangers in rooftop units with rust holes so big you could stick two fingers in it and the roll out wasn't tripping and others did trip a roll out with an itty bitty pin hole in a welded seam. Had a goodman last year that had a crimp ring cracked in half. Cool it looked like a good ring but once it warmed up the halves seperated 3/8th an inch, no roll out issues. Duracurves cracked in every cell would be another prime example.Pretty sure getting into the specifics on testing heat exchangers on an open forum isn't allowed here. That's why I strongly suggest taking the class. The boss has sent 9 of us through and recouped the fees in a week or less."


    Damage done on the details if you examine first part of post. Hahaha jk, and if no rollout issues then what seems to be the problem? (yes I understand CO IS DEADLY AND A CRACKED HEAT EXCHANGER IN THE RIGHT CONDITIONS IS NOT ACCEPTABLE) I guess I wonder what the reason you were called out on a unit and decided to inspect the heat exchanger because it wasn't tripped on the rollout? I have to admit I probably don't have enough experience on residents HX's as I do mostly commercial and neglected to realize this is the residents forum. But please provide your input. I have thanks

  6. #19
    hand held digital carbonmonxide ppm reader. drill small hole in flue pipe near furnace, insert sensor tip, turn on furnace. readings should level out around 50 ppm or less. when blower comes on and readings increase this means there is a crack in heatexchangere. or a blocked secondary heatexchanger. dont leave probe in to long readings will get to high for meeter and can cause damage. there is no need to look for a crack at this point. furnace or heatexchanger needs to be replaced.

  7. #20
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,743
    Quote Originally Posted by david c View Post
    hand held digital carbonmonxide ppm reader. drill small hole in flue pipe near furnace, insert sensor tip, turn on furnace. readings should level out around 50 ppm or less. when blower comes on and readings increase this means there is a crack in heatexchangere. or a blocked secondary heatexchanger. dont leave probe in to long readings will get to high for meeter and can cause damage. there is no need to look for a crack at this point. furnace or heatexchanger needs to be replaced.
    Often the CO reading will decrease when there is a crack or hole in the heat exchanger. Sometimes the CO reading will increase not because the HE is cracked, but because the air filer bracket doesn't have a cover and its drawing fumes back through the burners.
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  8. #21
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,050
    Quote Originally Posted by david c View Post
    hand held digital carbonmonxide ppm reader. drill small hole in flue pipe near furnace, insert sensor tip, turn on furnace. readings should level out around 50 ppm or less. when blower comes on and readings increase this means there is a crack in heatexchangere. or a blocked secondary heatexchanger. dont leave probe in to long readings will get to high for meeter and can cause damage. there is no need to look for a crack at this point. furnace or heatexchanger needs to be replaced.
    The CO reading on a furnace that has a cracked heat exchanger can do one of three things when the blower comes on; 1. It can rise, 2. It can fall. 3. It can stay the same.

    Not all cracks are leaking so you won't find them all with only a CO reading.

    And as Beenthere stated, there are other things that can cause erratic CO readings besides cracked heat exchangers.

  9. #22
    Join Date
    Feb 2012
    Location
    Toronto Canada
    Posts
    1,090
    Quote Originally Posted by david c View Post
    hand held digital carbonmonxide ppm reader. drill small hole in flue pipe near furnace, insert sensor tip, turn on furnace. readings should level out around 50 ppm or less. when blower comes on and readings increase this means there is a crack in heatexchangere. or a blocked secondary heatexchanger. dont leave probe in to long readings will get to high for meeter and can cause damage. there is no need to look for a crack at this point. furnace or heatexchanger needs to be replaced.
    I suggest you put down your fancy Co Reader and get an old fashion Mirror and use your eyes.
    How many "Upsales" do you get with that fancy trick? Might aswell have a Probe you stick in and a big Bad symbol lights up and tell the HO "Your Gonna need a new ones.This ones Bad see?" Sell them a new Furnace.

    I dont get the water trick? Pour it on the top and you will see it inside the burner tubes?

  10. #23
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    I was on one the other day, 15 yr old goodman piece o crap, flames rolling out, condensate box cracked and leaking. I told her it was time, old lady with money who lives on the lake and she gets pissed at me, it was In a crawl and I took pictures and showed her even. The part that made her mad was she put an inducer on 2 yr ago in an emergency. Why is it that the people with money always complain.


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  11. #24
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,050
    Quote Originally Posted by Joehvac25 View Post
    I was on one the other day, 15 yr old goodman piece o crap, flames rolling out, condensate box cracked and leaking. I told her it was time, old lady with money who lives on the lake and she gets pissed at me, it was In a crawl and I took pictures and showed her even. The part that made her mad was she put an inducer on 2 yr ago in an emergency. Why is it that the people with money always complain.


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    The next question they ask is, can't you just weld the crack shut???

  12. #25
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    Quote Originally Posted by chuckcrj View Post
    The next question they ask is, can't you just weld the crack shut???
    I usually tell them unless I have a few hose clamps, high temp silicone and an energy drink I really can't help them out lol.


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  13. #26
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,050
    Quote Originally Posted by Joehvac25 View Post
    I usually tell them unless I have a few hose clamps, high temp silicone and an energy drink I really can't help them out lol.


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