weighted damper issue?


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Old 04-29-19, 07:09 AM
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weighted damper issue?

I just installed a 6" vent system for my kitchen range hood.It's about 9' total with 1 90 elbow. While researching I saw mention of weighing down the wall exhaust end cap damper to minimize wind rattling noise.I decided to do this by super glue-ing a large washer to the outside of the damper. (It weighed about 2 quarters) All is working but I notice that the damper only opens up about 75% of the way up. I'm using the below vent (link). It's a 6" round to 3x10 opening. I'm thinking not an issue because if damper is open partially, wouldn't that just cause the air to flow faster thru the available opening? Is this an issue?

https://www.lowes.com/pd/IMPERIAL-6-...t-Hood/4598558
 
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Old 04-29-19, 08:28 AM
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Welcome to the forums.

if damper is open partially, wouldn't that just cause the air to flow faster
No..... not really.

The damper not opening fully is increasing the static pressure of the air inside the duct and technically slowing it down. It may not be enough to cause any issues with a strong exhaust fan.
 
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Old 04-30-19, 06:47 AM
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Thanx for the reply Pete! For peace of mind I removed the washer and the damper is still not 100% open, but it did rise a little more.The dollar store super glue that I used for securing the washer wasn't very super.The 1 time being cheap saved me some aggravation, the thing simply popped right off when I used a knife to pry it off.
 
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Old 04-30-19, 07:25 AM
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I know bath fans sometimes have their own damper but don't know about your range hood. If it does you might defeat it.

I have that same exhaust hood on my main bathroom exhaust, not yet active. I would thing a range hood would have no problem opening it. Do you know the cfm on that hood?

Bud
 
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Old 04-30-19, 01:34 PM
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Thanx for the input. Yes, the hood has its own damper, a butterfly like thing which both side fly open when fan is on. What do you mean by defeat it? The fan is rated as 750 cfm on high,which is way loud, set at low its still loud, but seems to be working.The exhaust is 10 feet up on the side of the house and can feel a healthy breeze from it. Truth be told, I could feel the breeze without removing the washer,so washer probably wasn't hurting it.
 
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Old 04-30-19, 03:23 PM
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Not sure how the internal damper functions, but it it moves out of the way using air pressure just like the outside damper then you may not need both. By defeating it I mean lock it in the open position so it is not restricting the air flow.

As a note, a 750 exhaust fan should have come with warnings if you did not see them and the related issue. That much air flow can depressurize a home sufficiently to backdraft other naturally drafted appliances. Feel free to ignore me if you are already aware of the issue.

Bud
 
 

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