Damper in bathroom fan making a lot of noise


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Old 02-24-19, 04:28 PM
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Damper in bathroom fan making a lot of noise

Hi,

In my bathroom I have a bathroom fan that looks like a Broan 678 series. My house was built in 1999 and fan is original.
https://www.broan.com/Bath-Vent-Fan/...79-Series/679L

The problem:
the damper inside the fan constantly makes a noise when there is a draft, wind outside. Or even on very cold days. Since the bathroom is next to master bedroom it affects sleeping.

Not sure what it is causing the damper to be so sensitive.
 
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Old 02-24-19, 05:28 PM
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The damper is very balanced so that outflow will easily open it and not restrict airflow. I've seen everything from it being removed completely to having a penny glued to it to having a hole drilled in it to try and alleviate noise. None of these are very satisfactory fixes.

Possibly an over sized hood over the outside vent would help. Even a simple "L" shaped wind block on one side (if it only happens with wind from a certain direction) might be effective Also, you might just want to inspect and clean the fan and damper assy. They can get pretty grungy which can affect operation.

I think in new fancy homes they actually have electrically operated dampers that only open when the fan is on. Dunno if that's possible in your case...probably isn't cheap.
 
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Old 02-25-19, 05:01 AM
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I like to keep a damper. I can feel the cold air coming in when it opens and fan is off.
The duct goes thought the insulated ceiling and vents though a soffit, distance might be 5 feet. The duct has a slight bend and the end to point downwards to soffit vent. I know not ideal, but would be difficult to reroute. I have a laundry room vent nearby that also vents to same soffit. Distance is slightly longer but same concept. Laundry room fan is more basic. Maybe something like this:
http://www.centralvacuumstores.com/m...Spec-Sheet.pdf
However, no noise coming from this fan.
 
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Old 02-25-19, 05:05 AM
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I have the same problem. I considered what Vic suggested but decided it wasn't worth the effort. I shut the bath door at night and just got use to it.
 
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Old 02-25-19, 12:07 PM
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Is it a common problem with all fans, or just with Broan?
 
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Old 02-25-19, 02:59 PM
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I think it's typical with any brand. Depends on the direction of the exhaust on the roof.
 
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Old 02-25-19, 03:25 PM
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Is the bathroom fan by default powerful enough to open two dampers?
Inside by the fan and outside like this?
https://www.homedepot.com/p/Everbilt...EVHD/203626521

In theory that woudl be better form an insulation perspective.
 
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Old 02-26-19, 01:30 AM
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I've never seen one like that, so don't even know how it operates. A higher capacity fan maybe, typical basic 50cfm (and thats an optimistic number) I kinda doubt it. Yours would be between the high and low end...it would be a pure guess.

 
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Old 02-28-19, 05:47 PM
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I have a Broan 678F/678F-F unt
50 cfm
2.5 sones

So, 50 cfm woudl not be enough?
 
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Old 03-02-19, 05:51 AM
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Just thinking about this. In case 50cfm is a no or maybe for pushing two dampers, I suppose I could remove inside damper and still end up with a better system?
 
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Old 03-02-19, 06:13 AM
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But that won't solve the noise problem.
 
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Old 04-07-19, 10:50 AM
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Came across this interesting note on page 3:
https://images.homedepot-static.com/...a82aa87c77.pdf

Looks like that the damper is open by 1" on purpose for UL requirement.
Is this the overall problem?


The duct connector has a counter-balanced damper flap. The flap will be “open” approx. 1” when duct connector is at-tached to housing. This design permits insulation to be in direct contact with fan/light housing per UL (Underwriters Laboratories) standards. The slightest backdraft, however, will close the damper flap, preventing air from entering unit or finished space
 
 

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