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  1. #1
    During my annual furnace maintenance service a crack was found in the heat exchanger. I was told I MUST replace the furnace, and the technician turned off the gas & removed a section of the supply pipe. In searching for info I found several references to furnaces being "prematurely" replaced as a result of "acceptable" heat exchanger cracks.

    This is a 1981 furnace, so I'm resigned to do the replacement, but my curiosity is aroused! I'm near Ottawa in Canada, so a reliable furnace is essential. Still, what constitutes an "acceptable" crack? Who makes the rules for "acceptable", or is this decided by emissions testing in the furnace compartment or at the registers. This particular hairline crack is just above the big openings where air is drawn into the combustion chamber, so I'm doubtful that there is any real risk from THIS crack... but a strong indicator that the rest of the heat exchanger is now suspect.

    Thanks for any insight.

  2. #2
    Join Date
    Dec 2002
    Location
    Houston,Tx.
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    15,912
    Originally posted by seventhson
    I found several references to furnaces being "prematurely" replaced as a result of "acceptable" heat exchanger cracks.
    If you believe there are acceptable deaths, well I guess you might be one to believe there are "acceptable" heat exchanger cracks.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

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  3. #3
    Originally posted by seventhson
    "acceptable" heat exchanger cracks.
    The above situation doesn't exists... you must be living in a fairy tale.

  4. #4
    Join Date
    Oct 2003
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    34.8n 102.4w
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    3,244

    Furnaces

    Are pretty cheap , compared to the damage they can do to both people and structures. Please do a search on carbon monoxide and read for the rest of the day...I bet monday you will get bids on a new furnace.JMHO.
    Life goes on long after the thrill of living is gone.

  5. #5
    Join Date
    Jan 2003
    Location
    Kansas City
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    1,482
    I have heard arguments from one of the major manufacturers' reps who spoke of acceptable cracks in heat exchangers, but I cannot agree. A furnace with a cracked heat exchanger may not leech carbon monoxide into the house, but It presents an inherently dangerous situation and should not be acceptable to anyone.-----Leaving a candle burning in the house while you are gone probably will not set the house on fire, but it is inherently dangerous----Carbon monoxide kills........

    [Edited by james mo on 08-14-2005 at 03:48 PM]

  6. #6
    Join Date
    Sep 2002
    Location
    South Dakota
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    6,579

    No manufacturer has any such thing as an acceptable crack in an exchanger!!!!


  7. #7
    Join Date
    Jan 2003
    Location
    Kansas City
    Posts
    1,482
    pro forum..

  8. #8
    Join Date
    Nov 2000
    Location
    Eastern PA
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    68,933
    OP, just where did you find information claiming that there are "acceptable" cracks in heat exchangers? Please post a link or give some sort of reference.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  9. #9
    Join Date
    May 2005
    Location
    Western Kansas
    Posts
    267
    I wouldn't want to be the tech that judged a crack acceptable and walked away from it. Talk about lawsuit fodder if something goes wrong and it gets worse over the winter.

  10. #10
    Nothing like "getting heat" from this forum!!!

    Here's one of the references I had, complete with source...

    --------

    http://www.cmhc-schl.gc.ca/publicati.../97-117-e.html

    "Marginal cracks are less apt to be properly diagnosed, and may result in adequate furnaces being taken out of service too soon..."

    Project manager: Don Fugler, (613) 748-2658

    ---------

    I know enough about CO to be suitably concearned. CMHC (in the URL above) is "Canada Mortgage and Housing Corp", who set many "guidelines" (to my knowledge they do not have legal force) for all aspects of residential and commercial buildings here in Canada. This statement was contrary to everything I had ever learned about heat exchangers. That's why I turned to this forum for enlightenment.

    I'm not about to flirt with fate for me and family, but the question still begs an answer... "Who makes the rules." Once I know that I can contact CMHC and Mr Fugler to request correction to this "authoritative" statement.

    Hope you can help!

  11. #11
    Join Date
    Jun 2004
    Posts
    258
    Originally posted by seventhson
    Nothing like "getting heat" from this forum!!!
    seventhson,

    The "heated" repies are true concern for you and your famlies saftey. I don't have the correct answers on who to contact, but the techs here are correct. In all my years in HVAC, I have never concidered any heat exchanger crack to be "acceptable". I've seen entire families get sick, and even some deaths from carbon monoxide poisoning. These were from some large and even some very small heat exchanger cracks. This isn't a situation where someone is trying to get money from you. It's codes law most anywhere to disconnect the gas line and tag it. most states here require that the tech contact the local gas company and advise them of the hazard as well. You seem like a very intelligent man. Make the right choice for you and your family and replace the heat exchanger or the entire furnace. You may not wake up some morning if you don't.

  12. #12
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,910
    the op may be talking about the front plate on that attaches to the actual chambers. Call your local inspection department or get a second opinion.

    My opinion: 1981 furnace, replace it. Or move to Ohio where we can't "steal" parts from your home. Only the inspection department has the authority to shut your gas off.
    No Heat No Cool You need Action Fast

  13. #13
    Join Date
    Jul 2005
    Location
    Wilmington, DE
    Posts
    355
    you would want to contact osha, there is not specific size at least in delaware, or anywhere else in the us that i know of. and in delaware there is a zero tolerance for crack in a heat exchanger, if you detect any amount of leaking co out of a heater it should be red taged and shut down and the ho should be advised that if the unit is turned on its at the home owners own risk, osha has standanrds of how much co is tolerable in the air in a structure, and they have the number of ppm parts per million and what happens to you i think in a house its considiered dangerous if you house hold air has more than 8 ppm and its hard to judge if there will be too much leaking from the furnice to take over the whole structure, but the only time you know if its too much is when you wake up dead,i just found a crack in a customer h/e and i detected 15 ppm in the duct, that guy was lucky because he had a heat pump and the gas furnace was only back up heat, there may be no min in canada for the size of the crack but as far as im concerned there is no acceptible crack and no manufacturer will disagree with that

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