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  1. #1
    Join Date
    Oct 2007
    Posts
    7

    Angry Will cracked heat exchanger cause flame to burn wires - second opinion

    So its time to fire up the furnace with the return of winter. The 11-year-old 80% Carrier makes all the normal sounds (first hear the motor for flue venting start, then flame ignites, and finally the blower fan). But wait -- I smell the awful smell of burnt wiring instead of the burnt dust you get after the summer rest. Pretty soon the smoke alarm goes off and the furnace shuts down.

    So, I get the smoke alarm to shut off and take the front panel off the furnace and see the burned wires. The tech came out and saw the wires and thought a deeper look necessary. He pulled the blower fan out of the unit -- crawled in its place and found the cracks in the exchanger. I expressed amazement that something much worse could be wrong. So, he went and got his fancy camera with the lense on the end of flexible probe and shows me the crack(s).

    So, looking for a second opinion. How likely is it that a cracked heat exchanger could cause the flames to deflect from the horizontal shooting (into the exchanger) and instead go vertical and start burning the wires above??

  2. #2
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,677
    very likely, but surprising that the rollout switches or pressure switch didn't keep it from happening, time to replace the unit, dollar for dollar, it would probably be the most logical decision. Make sure this one is sized properly, and you keep clean filters in the thing so it doesn't happen again.
    You can't fix stupid

  3. #3
    Join Date
    Apr 2007
    Location
    MN
    Posts
    297
    The fan will blow air into the heat exchanger through the cracks, which is now has positive pressure instead of negative. The positive pressure forces the flames to rollout and either burn wires, trip the rollout, or melt the fusible link. I would also recommend replacing the furnace due to cost.
    S**t or get off the pot!

  4. #4
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    you see the cracks and still ask
    yes to your question
    the real answer is no the unit can not be used unless the hx is replaced
    very unsafe the tech is right
    get a new unit

  5. #5
    Join Date
    Oct 2006
    Location
    Vallejo, CA
    Posts
    154
    Need to insure the gas pressure is adjusted at time of installation. All safety devices should be working properly and have written confirmation of these very important functions being performed! Regular annual maint. by a qualified tech should insure many years of safe service for your new system Oh yeah.." It's Hard To Stop A TRANE "

  6. #6
    Join Date
    Apr 2007
    Location
    MN
    Posts
    297
    "It's hard to pay for a Trane!"
    S**t or get off the pot!

  7. #7
    Join Date
    Nov 2007
    Location
    Sherman, TX
    Posts
    9,441
    Inshot burner heat exchangers gone bad are more difficult to diagnose by operation observation alone. But if your tech pulled the blower and showed you the holes, you really have no alternative.

    Inshot heat exchangers are new enough, that if you have one that's already bad, inadequate return air, or air flow are a definite possiblity that must be addressed.

    Was that a run on sentence?

  8. #8
    Join Date
    May 2005
    Location
    atlanta
    Posts
    31
    Deadly!!!! to have a crack heat exchanger, change the unit you will live and get a good preventy plan.

  9. #9
    Join Date
    Oct 2006
    Location
    Vallejo, CA
    Posts
    154

    Confused Huh?

    Quote Originally Posted by subcooled_ View Post
    "It's hard to pay for a Trane!"
    Financing!

  10. #10
    Join Date
    Apr 2007
    Location
    MN
    Posts
    297
    Quote Originally Posted by kellyr24 View Post
    Financing!
    OEM parts. I know, the same can be said of Lennox.
    S**t or get off the pot!

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,308
    Quote Originally Posted by cougar90 View Post
    So, looking for a second opinion. How likely is it that a cracked heat exchanger could cause the flames to deflect from the horizontal shooting (into the exchanger) and instead go vertical and start burning the wires above??
    Find that a lot.
    It probaly started to damage the wires last year.
    You need a new furnace.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  12. #12
    Join Date
    Oct 2005
    Location
    Omaha, NE
    Posts
    309
    I find it hard to believe that a HX on a 80% Carrier goes out in 10-11 y?

  13. #13
    Join Date
    Mar 2004
    Location
    SE Michigan
    Posts
    18,050
    Quote Originally Posted by cn View Post
    I find it hard to believe that a HX on a 80% Carrier goes out in 10-11 y?
    Why?...if its choked, it can take a dump alot faster than that.
    To put the world in order, we must first put the nation in order; to put the nation in order, we must put the family in order; to put the family in order, we must cultivate our personal life; and to cultivate our personal life, we must first set our hearts right.
    -- Confucius

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