Practical question regarding ductwork
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  1. #1
    Join Date
    Jan 2013
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    Practical question regarding ductwork

    So, I decided to install powerful inline fan in my attic capable of moving close to 3000 CFM and do air exchange every 4-6 minutes. This will be my whole house fan solution for the 2-nd floor only.

    I will install main trunk and then branch off to each individual bedroom/bathroom on a second floor. I have to use silencers because fan is definitely loud (seems like close to 70 db) and in addition to fan noise I would have to address aerodynamic noise coming from moving air @ pretty decent velocity through the ductwork.

    The immediate problem is that the largest available silencer off the shelf is only 12" and my fan requires 16" so I can't install it without further restricting air flow through both inlet and exhaust side of it.
    Secondly, I am torn apart what material/pipe to use as 16" galvanized pipe in 26 gauge is definitely not cheap and in addition I would have to spend extra time and money to further insulate it to reduce aerodynamic noise from air movement.

    Therefore I was thinking about insulated flexible pipe (very cheap and easy to install) but this one has its own issues as there are a lot of spirals/ridges inside it and in order to avoid potential problems I would have to increase its diameter from 16" to 18" or even 20" to reduce air velocity.

    So, what do I do? Any suggestions from Pro's?

  2. #2
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
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    6,007
    Where does the air replacing all this exhausted air come in at?

    Is this a belt drive centrifugal fan?

  3. #3
    Join Date
    Jan 2013
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    69
    The air comes from open windows and it is large inline fan, like Fantech FKD series which I believe is direct drive

  4. #4
    Join Date
    Feb 2011
    Location
    Georgia
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    186
    silencers only reduce sound of air velocity at terminals. not the sound of the fan if you were standing next to it or standing underneath it in your bedroom.

  5. #5
    Join Date
    Feb 2011
    Location
    Georgia
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    186
    70 db is no louder than the common TRANE condensing unit. Lol

  6. #6
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    Jan 2013
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    Hmm..exactly opposite to what I was told by Fantech tech support

  7. #7
    Join Date
    Feb 2011
    Location
    Georgia
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    186
    doubt they have ever installed one themselves
    Quote Originally Posted by ProperVenting View Post
    Hmm..exactly opposite to what I was told by Fantech tech support

  8. #8
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    Jan 2013
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    So what do I do?

  9. #9
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    Feb 2009
    Location
    Wisconsin
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    You have to fight through some bad days to earn the best days of your life.

  10. #10
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    Jan 2013
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    69

    Confused

    Quote Originally Posted by thermofridge View Post
    Because I do not believe in this solution as it implies that there is 1 (One!!) central location from where it is pulling all air. They are not powerful enuf and what happens when all bedrooms doors are closed. Where it will suck the air from??!!

  11. #11
    Join Date
    Feb 2009
    Location
    Wisconsin
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    310
    Quote Originally Posted by ProperVenting View Post
    Because I do not believe in this solution as it implies that there is 1 (One!!) central location from where it is pulling all air. They are not powerful enuf and what happens when all bedrooms doors are closed. Where it will suck the air from??!!
    What is wrong with one central location? How do you know they are not powerful enough? What happens with your design when some bedroom windows are closed? Where will it suck the additional cfm from? I am as confused as you. I have installed many of these and they are very quiet. I was trying to help by giving you an option. I did not think I was being anything but helpful. Good luck.
    You have to fight through some bad days to earn the best days of your life.

  12. #12
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,336
    Live with the noise, or enter the 21st century and install an hvac system.

  13. #13
    Join Date
    Jan 2013
    Posts
    69
    Quote Originally Posted by jtrammel View Post
    Live with the noise, or enter the 21st century and install an hvac system.
    If u refer to A/C and Heating system, I am already in 21-st century and I am installing this one in addition. And my last observation, you should be less presumptuous in your opinions.

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