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  1. #1
    Join Date
    Oct 2006

    I live in Louisville, Kentucky and recently bought a large house built in the early '90s. It has a RUUD Delux 90 Plus forced air natural gas heater. The master bedroom is on the first floor and there are finished rooms in the walkout lower level below the master.

    I've had the heat for only a couple weeks and have noticed at night (ambient temp in low 40's) that every time the heater kicks on, about 1 minute into the heat cycle a loud "pinging" noise comes from the vent on about 30 second intervals. It will continue the whole time the unit is on and then for maybe another 3 or 4 minutes once it shuts off. The HVAC unit itself is pretty far from where the noise is and I am pretty sure it is thermal expansion in the ducts. The ducts are your typical rectangular metal (sheet metal or whatever). They are the uninsulated but above the drywalled ceiling in our finished, heated lower level.

    The noise actually comes from two different vents - one that services the master bedroom and one directly under the master bedroom that services the room below. The thing sounds like chitty chitty bang bang driving through my bedroom at night and is driving my wife crazy.

    So the obvious questions....

    What exactly is causing this and is there anything I can do to fix it without ripping into the drywall? The rooms are nicely finished with crown molding, etc. - I really don't want to have to tear into all that. The main duct in that area is boxed in on the ceiling and the individual vents in question run between the floor joists.

    Please tell me someone has a solution???

  2. #2
    We had this problem in a new home. The professionals said it was either ducts expanding and once hot the expansion stops. Some thought that the ducts were resting against pipe in some places and the expansion was the friction. It was a new home and there were several instances where the carpenter shot nails through the duct work which restricts the ducts from expanding. I'm not a professional. We had the block the vents that had the most noise. Tough problem to have.

  3. #3
    Join Date
    Aug 2006
    I had this same experience. It was the ducts screwed tight to the floor joists. I was able to loosen the screws up and lower the ducts alittle and the noise went away. bummer about the drywall. Can you see from an end how they are fastened and if they are tight to the joists?
    Buy American! The job you save may be your own.

  4. #4
    Join Date
    Nov 2004
    Naples, Fla.
    While I don't have 1st hand experience w/ your particular furnace.. it's obvious the common denominator to your conundrum is HEAT (expansion). In most cases this is expressed as a "tin caning" where the metal is simply buckling from the expansion.

    Now the part subjected to the most sever temp swing is the heat exchanger or burner rails. If the HX is the culprit, your only remedy will be a new HX or furnace. If you've deducted that the noise is actually coming from the ducts, it's going to be a process of elimination to isolate & eventually remedy the ping. During fabrication, most contractor's cross break the metal panels to add rigidness & reduce these types of nuisance issues.

    If it's actually duct work expanding beyond where you can reach to secure it, you'll have to gain access from above or below.

    Or -- turn up the TV

  5. #5
    Join Date
    Sep 2002
    I don't know
    I know this is a half fast "solution", but what the hell...

    Install a programmable t-stat and set it back so the furnace doesn't come on much at night.

    You could try loosening the screws (or taking a couple of nails out) which hold the register boot to the subfloor to allow for more unrestricted expansion/contraction.

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