# A noisy damper?



## Toller (Jan 2, 2013)

One of the two ducts to my bedroom was making a repetitive banging noise whenever the heat came on.
A plumber at my house for another reason looked at it and found a loose seam on a trunk that fed the noisy duct but not the quiet one. He banged on it with a hammer and it got much quieter for a day but then got noisy again.
I called the duct manufacturer and they said to put some screws into the seam to stop it from moving. I did, and 90% of the banging went away.
But an occasional bang, rather like hitting the duct with a small tool, remains.

Over the last week I have been tracking down more loose seams and screwing them, but it doesn't help at all. 
There was one part on the duct that connected to the floor that oil canned easily, so I put a bunch of duct tape on both sides, but it still banged.

All I can figure now is that it is the damper. I have it tightened as much as it will go, but it still bangs if you tap on the duct; so I figure it is still free to bang when the heat is on.

There is no obvious way to get at the damper without pulling down the whole duct line, about 15'; and I really don't want to do that.

Any suggestions for:
1) getting at the damper without pulling down the whole duct line
2) what else could be banging.

Thanks much.


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## how (Feb 26, 2011)

post photos.


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## jmon (Nov 5, 2012)

Did u check on top of ductwork for tools, etc. that could be making noise? Found a couple links that may or may not help u.

link here 1


link here 2


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## ben's plumbing (Oct 6, 2011)

did you check to see if the air movement inside furnace is sucking the ductwork in and letting it go when it stops. expansion and contraction...bang...ben sr


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## Toller (Jan 2, 2013)

ben's plumbing said:


> did you check to see if the air movement inside furnace is sucking the ductwork in and letting it go when it stops. expansion and contraction...bang...ben sr


No. Running the blower alone does nothing.
The banging is every few minutes while the heat is on.

I did find a section of the trunk about 20' from the vent that could be oil canning. Is it reasonable to screw something to that to keep it from moving? I don't know if it is actually doing anything, just that it could be moving; only way to rule it out is to "fix" it. Or so it seems to me.

I will take some pictures tomorrow.


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## Toller (Jan 2, 2013)

The banging is gone!
I put a hose clamp right after the damper and it reduced the loudness of the banging. I put another right before the damper and it eliminated the banging. So I am all set.


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