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  1. #27
    Join Date
    Feb 2004
    Location
    Maine
    Posts
    483
    The location of the crack also makes a difference. Also a "marginal" crack can open up wide with no warning. Any crack in a heat exchanger and the heat exchanger must be replaced, or a new furnace put in. As others have stated find out why the one you have now cracked. Could be an airflow issue from inadequate ductwork causing to great of a temperature rise. Airflow issues must be corrected before a new furnace is put in, or you will end up with a cracked heat exchanger on your new furnace.

  2. #28
    Join Date
    Aug 2002
    Location
    Westlake, Ohio
    Posts
    2,470

    Cracked Heat Exchanger

    If all heat exchanger leaks were dangerous every new clamshell heat exchanger would be condemned the day it was put in. In the 1980's it was determined by AGA, GAMA, GRI that 1/8" cracks were okay. The 9ppm of CO in the living space was created so new heat exchangers could have leaks. 60%-70% of all CO poisoning are caused by water heaters and boilers, then come unvented heaters and ovens. Cracked heat exchangers don't make CO. Poor service and lack of testing and knowledge makes 99.99%.
    captain CO

  3. #29
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,941
    So Jim, is that 1/8" long or wide cracks? Also, newer heat exchangers are not purposely made to "leak", they are made to "give" so that cracks do not occur in the thinner materials needed for efficient heat transfer. Once a heat exchanger heats up it should be pretty air tight.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  4. #30
    Originally posted by RoBoTeq
    newer heat exchangers are made to "give" so that cracks do not occur in the thinner materials needed for efficient heat transfer.
    I wonder how Thermopride still uses their heavy HX, but yet have the same 'high' efficiencies as the rest of the companies?

  5. #31
    Join Date
    Aug 2005
    Posts
    831
    Originally posted by jultzya
    Canadian....

    Carbon Monoxide Concentrations
    CO concentration in parts per million (ppm) Effects
    0-2 Normal conditions in and outside Canadian houses.
    11 Maximum tolerable indoor concentration over an eight-hour period.1
    25 Maximum allowable concentration for continuous exposure for healthy adults in any eight-hour period.1
    30 CO detectors must not sound alarm within 30 days.2
    70 CO detectors must sound alarm within one to four hours.2
    150 CO detectors must sound alarm within 10 to 50 minutes.2
    200 Slight headache, fatigue, dizziness and nausea after two to three hours. CO detector alarm must sound within 35 minutes.3
    400 CO detectors must sound alarm within four to 15 minutes.2
    800 Dizziness, nausea and convulsions within 45 minutes, death within two to three hours.3
    1600 Death within one hour.3
    13,000 Danger of death after one to three minutes.3

    1 Exposure Guidelines for Residential Indoor Air Quality, Health Canada, 1989.

    2 From CAN/CSA 6.19, Residential Carbon Monoxide Alarming Devices, 2001

    3 Carbon Monoxide Poisoning, Iowa State University of Science and Technology, AEN-172
    Is that "not" for "30" CO a typo?
    eventu rerum stolidi didicere magistro

  6. #32
    Join Date
    Dec 2000
    Location
    Sudbury Ontario, Canada
    Posts
    155

    cracked heat exchanger

    There should be no discussion here. You are in Ottawa so you are under CSA B149 Code Series. The code states
    Code 3.21.1
    "Where the heat exchanger of a furnace installed in a dwelling unit is found to be defective, it shall be replaced."
    That is all there is to say about this.

  7. #33
    Join Date
    Sep 2002
    Location
    South Dakota
    Posts
    6,579


    I have been told that you can take most new heat exchangers out of a furnace, turn them upside down and fill them with water and they will leak.

    However,when they are heated the expansion causes them to tighten up so they do not leak.

    Would like Jim Davis to comment on this.

    Norm

  8. #34
    Join Date
    Jul 2005
    Location
    North Central Ontario Canada
    Posts
    624

    Thumbs down

    we were told by icp (keeprite) that a large crack found in the vestibule above the burners was ok.

    our warranty claim was rejected! old part sent back. never mind the potential for spillage from that area as it was directly above the crosslighter and spark pilot!

    yes it was in central ontario...3 years ago.

    we had lennox tech support tell us to go ahead and condem every duracurve heat exchanger 'cause they are probably cracked. nice way to talk about your product. they are very difficult to inspect if there is an evap mounted right on top of the furnace.
    Here's your sign...

  9. #35
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,941
    Originally posted by NormChris


    I have been told that you can take most new heat exchangers out of a furnace, turn them upside down and fill them with water and they will leak.

    However,when they are heated the expansion causes them to tighten up so they do not leak.

    Would like Jim Davis to comment on this.

    Norm
    This is exactly what engineers from three different manufacturers of furnaces have confirmed to me. There is no doubt that most heat exchangers today will not hold water when cold.

    I am not familiar with Thermopride so I cannot answer the question about them.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  10. #36
    Join Date
    Apr 2004
    Posts
    7,680
    Todays furnaces are also under a negative pressure proved by a pressure switch. A crack in an older furnace may have allowed air from the blower into the combustion cham ber which could easily roll out either at the draft diverter or out through the burners. The manufactures dont hesitate to replace a cracked hx under warranty either or in the case of availability offer a credit. Todays burners also dont generally have an adjustment on the air mix. 20 years ago CO detectors were rare at best in homes and many service guys didnt have the tools either. Homes were not as tight as they are now either. I'm sorry but there are few similarities between then and now. A Crack is a crack is a crack is the only similarity.

    I have yet to see a lennox duracurve without a hairline crack or worse in the far right cell. Many of the Carrier 58ES have popped spot welds at the dimples or cracks in along the back wall. Sorry to say but the 80's produced alot of junk from furnaces to the K car. High inflation forced quality to take a backseat to price.

  11. #37
    Join Date
    Feb 2004
    Location
    southern illinois
    Posts
    5,522
    ....wouldn't this be more reason to combustion test?,..i was told this was acceptable at seminar a couple months back about the 1/8 inch crack,if i left this crack even if it was burning clean,wouldn't this be negligence on contractors part when crack got bigger down the road,God forbid......i don't see how a guy is supposed to be able to take responsibility for a crack,...either way i was taught if it's got a crack it gets shut-down period.

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