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squished18 02-05-2007 04:59 AM

noise from vicinity of range hood
 
Hello,

I have a problem that I'm looking for some suggestions on solving. On windy days, I get noise from somewhere along the exhaust duct of my range hood. It gets noisy enough such that it interrupts my sleep, as my bedroom is right above this exhaust duct.

I suspect it may be a backdraft damper that is the source of the noise. The exhaust duct vents onto the side of the house. I'm guessing that when it is windy, there is significant wind between my house and my neighbour's. This causes wind shear across the opening of the vent. The wind shear then causes pressure changes that cause the backdraft damper to open and close. As this has been happening for years, there is probably significant friction between the parts of the backdraft damper, generating the squeaky nosie.

Has anybody had a similar experience and was able to solve it? Any assistance would be appreciated.

Thanks,
squished

#CARRIERMAN 02-05-2007 02:09 PM

Hi squished18

When you get a direct enough wind it will cause the damper to shutter and make a growling noise. Sometimes you can put a wind break over top of it with a open top and bottom to stop this. Keep in mind if this is what you want to do, it will cause oil buildup on your exterior wall and needs to be made out of sheet metal. Hope this helps answer your question.

Good luck
Rusty

tvlfleming 02-06-2007 07:00 PM

If it is a metal damper replace it with a plastic one or search for one with a spring loaded door.

squished18 02-07-2007 10:38 PM

Thanks for the suggestions!

squished

kmah 12-30-2009 03:32 PM

I also have the same problem...

When winds are strong about 60 km/h and up, the damper/flapper vibrates against the house with a loud noise. I've tried everything from enlarging the weather cover with some metal flashing, but still doesn't work. Our exhaust is at the side of the house.

I've tried to find a spring-loaded damper to no avail.

I've come up with another idea... is to use magnets. I will install an L bracket inside the vent with a magnet attached to it, and will install an attracting magnet to the damper itself and line the 2 up just right. If I can just get the magnets at the right strength -- so that the damper can still open when the hoodfan is turned on, then I'm golden. The idea is to have enough force so the wind cannot pull the damper open and cause the flapping motion. We have one of those turbine hoodfans with 800 cfm, so it should be enough force to pull it open. With the magnet, I'm hopeful that it will work.

I'm hoping to try this out in the next few weeks to see how it works.

kmah 01-25-2010 09:06 PM

Yes it works!
 
I installed the L-bracket inside the vent with an small ring shaped earth magnet and did the same on the flapper. The screws that attach the magnet give it some distance so the strength isn't too strong. After a day of 60km/hr gusts, we hear no more flapping! I'm waiting for the 100km/hr wind gust now to really test the thing.

There is 1 drawback, we do have to turn the hoodfan on "high" to force the vent to open, but afterwards, you can set it to "low" once it opens. You can hear the rush of air push the vent open. Also, when it closes, you can hear a slight tap of the screws touching each other.

A good and cheap and simple solution compared to the Hoyme Motorized damper I was contemplating on getting. :laughing:

505jrb 04-19-2010 11:20 AM

Noise from vicinity of range hood
 
I am also trying to conquer a noise and draft problem from a range hood. The house is on top of a ridge subject to high winds. The Vent-A-Hood has a gravity-type damper, and the 10" duct goes through the roof. I have changed the vent cap to a more covered design, but this didn't help. I then mounted a FanTech spring-loaded damper where the duct comes through the roof and added 30" of vertical duct to get the cap well over 2 feet above a nearby parapet. The FanTech damper is very well-made and includes Neoprene seals. This made some improvement, but I am still getting a back-draft (and resulting noise from the flapping dampers) when it is windy. Any other ideas?

Yoyizit 04-19-2010 01:05 PM

For positive closing/opening you could try a 24vac solenoid, linear or rotary; then you have a home-brew motorized damper. Try places like Hosfelt.com for parts. Your labor time for this project could be two hours, depending on your skill level. Parts, $20. . .?

505jrb 04-20-2010 12:15 PM

Noise from range hood
 
Thanks for the suggestion. This hood is housed in a plastered enclosure, so the only practical access for a solution is from the roof. I thought about an electrically-operated damper, but the only waterproof ones I could find were VERY expensive. And, the 10" FanTech damper I installed has 2 semi-circular baffles (that both pivot upwards), so it would be difficult to motorize. My latest thinking is to fabricate a large, well-baffled cap for the top. The duct is almost 80 square inches in area, so the cap would have to have at least this much open area. The area would preferably be considerably bigger than that to minimize the negative pressure created by the significant wind we can have blowing past it. The more that the pressure differential can be minimized, the less flapping of the damper baffles and less air noise will occur.


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