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  1. #1
    Join Date
    Dec 2010
    Location
    pittsburgh/butler
    Posts
    33

    carrier meltdown

    Have you seen or experienced a melt down of the black plastic air in take or pvc air intake on 58mca furnace. The plastic has melted even in the burner box sight glasses.

  2. #2
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    913
    Quote Originally Posted by hvacart View Post
    Have you seen or experienced a melt down of the black plastic air in take or pvc air intake on 58mca furnace. The plastic has melted even in the burner box sight glasses.
    I've had the plastic sight glass melt. All due to clogged secondary heat exchangers on them. Check for carbon monoxide in the flue, you'll usually have a nasty smell outdoors as well. Either case, that furnace is potentially unsafe!

  3. #3
    Join Date
    Dec 2010
    Location
    pittsburgh/butler
    Posts
    33
    Taken pictures but no sense in taking co readings just red taged the furnace. Had not seen a meltdown like this as the safeties failed. The heat melted the black box to the point that the pvc attached melted too. The co is always a good indicator of the secondary failure. We are seeing far to many. Now what? Do you rebuild or libable

  4. #4
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    913
    Quote Originally Posted by hvacart View Post
    Taken pictures but no sense in taking co readings just red taged the furnace. Had not seen a meltdown like this as the safeties failed. The heat melted the black box to the point that the pvc attached melted too. The co is always a good indicator of the secondary failure. We are seeing far to many. Now what? Do you rebuild or libable
    they get red tagged immediately. Based on the circumstances, I will advise a replacement furnace. I'll always quote the repair costs for it and let the HO decide.

    All the ones that had the plastic sight glass melt tripped the roll out switch, never had one where the safety failed to open and melted the PVC or air intake box....

  5. #5
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,854
    clogged secondary!

    only thing i can suggest is to make sure the furnace is pitched forward and you use a combustion analyzer to tune it!

  6. #6
    Join Date
    Dec 2010
    Location
    pittsburgh/butler
    Posts
    33
    My problem with all this is there are twenty plus furnaces in this location some horizontal some vertical. The drainage issue is well known but I have never seen a melt down usually the roll out protector would trip. The idea that the furnace needs to be pitch to guarantee secondary drainage not very acceptable. How do you deal with prior installations. The co test of the exhaust tells you that the exchanger is done.
    What about the liability and how do you change the secondary on a horizontal furnace
    that is 10 feet in the air.

  7. #7
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,854
    you pull the furnace down, replace the guts, then re-install it.

  8. #8
    Join Date
    Dec 2010
    Location
    pittsburgh/butler
    Posts
    33
    Just finished replacing the furnace. We are talking to Carrier about adding a second roll out protector for the remaining furnaces. We will examine this furnace for secondary blockage. Will keep you advised.

  9. #9
    Join Date
    Apr 2012
    Posts
    44
    Did u test the roll out switch? Being as unit installed horizontal, was the RO switch on the bottom side of burner box? They trip more often when on upper side of box, for obvious reasons.

  10. #10
    Join Date
    Dec 2010
    Location
    pittsburgh/butler
    Posts
    33
    As you have indicated; we know the rollout failed since the melt occured. The rollout is on top of the burner box in this horizontal installation. But until we examine the furnace on the ground we don't know if the wires melted together or if the thermal device just failed. Carrier is replacing the furnace with a new unit and will advise us further once we send back the unit.

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