Welding a Heat Exchanger

Discussion in 'HVAC Heating & Cooling' started by molo, Sep 18, 2009.

  1. molo

    molo Member

    Messages:
    857
    Location:
    cold new york
    Can this be done with a safe result? There is a 4" crack running up from the lower left corner of a heat exchanger on a stand alone Empire furnace. I want to be safe but if it can be done safely I may contact someone to do it.

    Thanks for any replies
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Welding cast iron is possible, but requires certain skill and the right equipment. Unless you are a skilled welder, I suspect it would cost you almost as much to have it repaired, as to just get a new furnace.
  3. Gary Swart

    Gary Swart In the Trades

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    7,397
    Location:
    Yakima WA
  4. molo

    molo Member

    Messages:
    857
    Location:
    cold new york
    OK, Thanks for the responses. It doesn't sound like a good idea. Why do they make them so thin? This is an Empire that isn't that old and it's cracked!
  5. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    How old?
    How did you discover the crack?
    Does your furnace have a flame rollout switch?
  6. molo

    molo Member

    Messages:
    857
    Location:
    cold new york
    It might be 10 years old. It is a vented stand-alone furnace about 3' high and 4' wide. We noticed the crack during a cleaning and inspection. I do not know if it has a flame rollout and I know this heater has been used with this crack.
  7. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    Anyone have CO symptoms? Any CO alarms went off?
    Only 1/6th of resi. HVAC stuff dies this early.

    My '82 furnace with no flame rollout switch was just checked and the tech found nothing wrong but I don't know how thorough a furnace inspection has to be to show "Due Diligence" and "Duty of Care".
    He didn't disassemble any panels and I am going to replace my old CO detector.
    Only 1/4th get to be as old as my NG furnace but he said this age wasn't unusual in my area.
    Last edited: Sep 18, 2009
  8. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    Heat exchangers on forced air furnaces are rarely, if ever, made from cast iron. Mostly they are "aluminized" sheet steel, aluminized to reduce rusting. They are thin to promote heat transfer to the passing air stream. Rarely is welding a cracked heat exchanger successful as they will usually crack again either through or right along the weld.

    The one thing that is most common in promoting cracking is a blower set to too low an airflow for the heat input.
  9. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego

    Don't know his model specifically, but Empire makes top gravity vent wall furnaces. Nonetheless, I agree that the heat exchanger might be cast, or it might not.
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