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Thread: Loud furnace

  1. #1
    Join Date
    Mar 2018
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    Loud furnace

    I've come across two furnaces this season with the same issue. Generally this will only happen on very old standard efficient furnaces.

    Pilots lit, stat calls, valve opens, burners light. Now instead of a pop or bang (due to incomplete combustion or duct expansion?) Before the fan limit kicks on - I would hear a very loud humming.

    One again the heat exchanger wouldnt of been hot enough to activate the fan cycling switch yet and almost immediately you would hear a very loud humming - almost through out the whole house?

    If tried manually pushing the fan cycling switch in and the fire sequence once more - still super loud humming ( with and without fan running).

    Is this a cause from a cracked heat exchanger or something worth condemning a unit? Not that I would have but I would like to know the root of this occurrence.

    Last question - can someone give me a good description of aldehydes - what I should be looking / smelling for? Still very uncertain of what to look for in the cases of crack heat exchangers.

    - any help is appreciated

  2. #2
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    Mar 2018
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    Burner noise. caused by the gas air mix as it goes thru the holes in a ribbon burner creates a sort of frequency. You may have too much air mixing. Get a senior tech to go with you and learn ya how we did it in the days way back.

  3. #3
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    Oct 2015
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    Yep I remember that burner hum on cold burners until they got warm. They would hum for about 10 seconds up till about 45 seconds then they would quiet down. Some high efficiency units did this also too. Heil and Yorks I know did this for sure.
    There is only one truly right way to do something, but there are thousands of wrong ways to varying degrees to do it.
    So the question is: If you don't do it right, then how wrong is it going to be???

  4. #4
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    Oct 2011
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    Gladstone, Oregon (Portland)
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    Yep. Adjust the mixture and it will go away. Check static while you are there as well. A combination of that and quieting the ducts will make your customer happy.

  5. #5
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    Mar 2018
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    Quote Originally Posted by Robber View Post
    Yep I remember that burner hum on cold burners until they got warm. They would hum for about 10 seconds up till about 45 seconds then they would quiet down. Some high efficiency units did this also too. Heil and Yorks I know did this for sure.
    I remember York and Frazer- Johnson having to re-design the burner with a different flute (crimp)on the bottom to correct an issue back in the early 80's.

  6. #6
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    Jun 2011
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    it's some kind of resonating harmonics .....

    I have encountered this on older single cast iron burners until they heated and just though it was normal ..... check your gas pressure and set your mixture
    "All that is necessary for the triumph of evil is that good men do nothing." (hvacrskills)


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