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  1. #1
    Join Date
    Feb 2010
    Location
    Ontario Canada
    Posts
    1,339

    Cracked heat X ????

    A cracked heat exchanger can be a bad situation. But with the newer furnaces that are essentially negative pressure, is there any harm? Today I found a heat exchanger, 16 years old, very rusty on the inside with seems that are 1/8 to 1/4 inch separated. No indication of a crack, but it made me nervous just looking at it. I brought the customer down to the furnace and explained that although I could not find a definitive crack, my gut feeling is that if I pulled the furnace out, I would find one. I used the bore scope and could see signs overheating. I red tagged it.
    Questions. How far do you go to find a crack if you suspect one? What do you let go?
    Never give up; Never surrender!

  2. #2
    Join Date
    Oct 2011
    Location
    South Carolina
    Posts
    31
    Id look at it if it were my own. The risk of running it would be too dangerous and i would tell the customer that. Its all about safety and my family comes first. I always go with my gut feeling. Sometimes the naked eye can't see everything but your gut instinct is usually right.

  3. #3
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,050
    I don't red tag them just for rust, but I certainly stress to the homeowner that their furnace will be unsafe shortly and now would be the perfect time to replace it.

  4. #4
    Join Date
    Aug 2011
    Location
    Eastern Shore, MD
    Posts
    798
    Furnaces have all ways been in a negative pressure... It's not co spilling out of a crack that should worry you. It's flue gases backing up due to air being Pulled in brought the failure causing high levels of co or flame roll out. According to the AGA....ANY failure is well enough to red tag a furnace

  5. #5
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,050
    Quote Originally Posted by Gross View Post
    Furnaces have all ways been in a negative pressure... It's not co spilling out of a crack that should worry you. It's flue gases backing up due to air being Pulled in brought the failure causing high levels of co or flame roll out. According to the AGA....ANY failure is well enough to red tag a furnace
    A rusted heat exchanger is not a failure if there is no "visible crack or hole".

  6. #6
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    rusted hx needs a good cleaning and vacuming out then check to see if a crack is there
    have seen many a rusted hx lennox and carrier mostly but could not find ant cracks just poor draft in most cases

  7. #7
    Join Date
    Jan 2011
    Location
    Boston, MA
    Posts
    459
    Quote Originally Posted by tinknocker service tech View Post
    rusted hx needs a good cleaning and vacuming out then check to see if a crack is there
    have seen many a rusted hx lennox and carrier mostly but could not find ant cracks just poor draft in most cases
    How do you clean and vacuum a heat exchanger? Esp. those with tight enclosed burner boxes?

    Also anyone have any tips on checking secondary HX's?

  8. #8
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    Quote Originally Posted by FrostyBeer View Post

    Also anyone have any tips on checking secondary HX's?
    I check secondary hx's by pulling the blower and getting in there. White lime scale looking deposits are a dead give away of a leaker.

  9. #9
    Join Date
    Dec 2011
    Location
    Toronto
    Posts
    11
    Quote Originally Posted by chuckcrj View Post
    A rusted heat exchanger is not a failure if there is no "visible crack or hole".
    What type of heat exchanger is it? When you open up the supply duct and look at it are the seams folded and welded. Because those particular H/E are tanks and seem to last. With a bore scope through the burner section they look cracked but indeed they are not.

    I agree no visible crack or hole = No red tag

  10. #10
    Join Date
    Jul 2001
    Location
    Central MN and the Twin Cities
    Posts
    1,530
    Quote Originally Posted by Gross View Post
    Furnaces have all ways been in a negative pressure... It's not co spilling out of a crack that should worry you. It's flue gases backing up due to air being Pulled in brought the failure causing high levels of co or flame roll out. According to the AGA....ANY failure is well enough to red tag a furnace
    Not true.... there are some furnaces that are positive pressure.
    Warning: Just because I am over the head injury doesn't mean I'm normal!

    The day I stop learning.... I'm dead!

  11. #11
    Join Date
    Aug 2011
    Location
    Eastern Shore, MD
    Posts
    798
    Quote Originally Posted by grasshopper View Post
    Not true.... there are some furnaces that are positive pressure.
    which ones?

  12. #12
    Join Date
    Dec 2011
    Posts
    33
    Quote Originally Posted by Gross View Post
    which ones?
    only lennox pulse that I can think of

  13. #13
    Join Date
    Aug 2007
    Location
    Okmulgee, OK
    Posts
    184
    Trane Voyager positive pressure forced draft. But it depends on where the crack is at that can determine if the air from the blower motor is entering the heat exchanger or pulling flue gases from heat exchanger and putting them in the airstream.
    It's just rocket science. It's not like it's heat and air work or something.

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