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  1. #14
    Join Date
    Apr 2012
    Location
    Millsboro, DE
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    When a system is designed there's typically an ACCA, SMACNA and/or Code requirement for branch dampers. Balancing at the outlet is usually prohibited because of the noise issues and the fact that many devices can't be locked in position. I also don't like them because they're accessible to those "cold" or "hot" occupants.

  2. #15
    Join Date
    Apr 2012
    Location
    Millsboro, DE
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    I have a friend who inserts round ceiling diffuser dampers in floor diffuser boots where there're no (accessible) branch dampers, says they work fine. I believe that complies with the SMACNA requirement for locking, but the additional PD scares me.

  3. #16
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
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    Face dampers certainly are not preferable but in some cases are necessary and are generally not noisy unless the diffuser and branch duct are oversized. Most face dampers are self locking but most used in residential floors are not.
    When I ran into a diffuser with a face damper that was short of air I could get on average about 20 CFM more by removing it and I removed several.
    No man can be both ignorant and free.
    Thomas Jefferson

  4. #17
    Join Date
    Apr 2012
    Location
    Millsboro, DE
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    LOL! That's my last resort when all else fails: The additional 0.03" can make a big difference.

  5. #18
    Join Date
    Apr 2012
    Location
    Millsboro, DE
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    With today's homes running as much as 1,350+ SF/Ton, a lot of sizing issues have arisen: Manufacturers just don't make small enough stuff.

    I wrestled with how to deliver only 12 CFM to an outlet (closing a 4" branch damper and its 2-1/4x10 floor diffuser multiblade damper still gets you 15 or 20 CFM) for hours. Then a great tech I'm working with came up with a simple solution, bless him: He uses a 2" hole saw instead of cutting a 4" hole for the 4" adhesive collar, providing the ability to dial in whatever we need.

    12 CFM being the ACCA residential balancing tolerance (10 cfm x 120%) for my specing an outlet in small rooms with limited exposures to outdoors (less than 10 CFM required, no outlet - I'm sure everyone here is OK with that).

  6. #19
    Join Date
    Mar 2015
    Location
    Hamersville, Ohio
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    7,281
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    How small is that room, that only requires 10CFM Ferd?

    Are You conditioning a broom closet?
    Hos 4:6 My people are destroyed for lack of knowledge. Because you have rejected knowledge, I will also reject you, that you may be no priest to me. Because you have forgotten your God’s law, I will also forget your children.


    "You've got to Stand for Something or You'll fall for anything" (A. Tippin)


    Mat_15:24 But he answered, “I wasn’t sent to anyone but the lost sheep of the house of Israel.”

  7. #20
    Join Date
    Apr 2012
    Location
    Millsboro, DE
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    181
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    The 10 CFM rooms are water closets in large bathrooms (a room housing the WC, not the fixture inself) large walkin closets, mud rooms, powder rooms, pantries, etc. all with a little exposure to outdoors. Haven't done a Broom Closet yet, but I have seen two 4x10x6 serving a small WIC with no outside walls.

    400 CFM/Ton at 1,000 to 1,350 SF/Ton = 0.40 to 0.30 CFM/SF, so 25 to 33 SF.

    Thanks for asking.

    FYI: I work with one main installer, who's buying 2-1/4x10's, 4" and 5" duct in quantity.

  8. #21
    Join Date
    Sep 2008
    Location
    VA
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    3,551
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    I agree with Wayne, the mold thing is bogus. Moisture is related to the temperature of the air and the ambient RH% in the home. If you have supply air temperature below dewpoint then you're likely to have sweating supply grilles.

    So what do our brilliant manufacturer engineers come up with to reduce indoor humidity???

    Yeah! Let's sell overpriced variable speed blowers that decrease air speed which in turn creates a lower supply air temperature! Great, our indoor humidity level is a whopping 3% lower, and now we have moldy registers!
    "The only true wisdom is in knowing you know nothing" Socrates

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  10. #22
    Join Date
    Apr 2012
    Location
    Millsboro, DE
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    181
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    MG: The Industry is experiencing an exponential increase in service and repair business created by the high tech stuff installed by guys from the Alpha Hotel, but most contractors (sorry, people) ignore the business opportunity to correct the root causes (oversizing, 0.10" friction, duct workmanship, high resistance fittings, etc.), which would help their customers and generate "Word of Mouth" referrals.

    Now if there was an associated exponential increase in Qualified techs who could service the stuff...

  11. #23
    Join Date
    Mar 2015
    Location
    Hamersville, Ohio
    Posts
    7,281
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    Quote Originally Posted by ferd1942 View Post
    The 10 CFM rooms are water closets in large bathrooms (a room housing the WC, not the fixture inself) large walkin closets, mud rooms, powder rooms, pantries, etc. all with a little exposure to outdoors. Haven't done a Broom Closet yet, but I have seen two 4x10x6 serving a small WIC with no outside walls.

    400 CFM/Ton at 1,000 to 1,350 SF/Ton = 0.40 to 0.30 CFM/SF, so 25 to 33 SF.

    Thanks for asking.

    FYI: I work with one main installer, who's buying 2-1/4x10's, 4" and 5" duct in quantity.
    Please define " large bathrooms", ... length, width, height, conditioned walls/ unconditioned walls/ insulated crawl/ Basement/ Insulated attic/ Conditioned Space above.

    I'm asking cuz', ... I've never seen a "Large Bathroom" get a S/A that delivered 10CFM only. The "Fart Fan" that exhausts most bathrooms pulls at least three times that amount of air.
    Hos 4:6 My people are destroyed for lack of knowledge. Because you have rejected knowledge, I will also reject you, that you may be no priest to me. Because you have forgotten your God’s law, I will also forget your children.


    "You've got to Stand for Something or You'll fall for anything" (A. Tippin)


    Mat_15:24 But he answered, “I wasn’t sent to anyone but the lost sheep of the house of Israel.”

  12. #24
    Join Date
    Mar 2015
    Location
    Hamersville, Ohio
    Posts
    7,281
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    Quote Originally Posted by mgenius33 View Post
    I agree with Wayne, the mold thing is bogus. Moisture is related to the temperature of the air and the ambient RH% in the home. If you have supply air temperature below dewpoint then you're likely to have sweating supply grilles.

    So what do our brilliant manufacturer engineers come up with to reduce indoor humidity???

    Yeah! Let's sell overpriced variable speed blowers that decrease air speed which in turn creates a lower supply air temperature! Great, our indoor humidity level is a whopping 3% lower, and now we have moldy registers!
    My "Modified Like Button" >>>
    Hos 4:6 My people are destroyed for lack of knowledge. Because you have rejected knowledge, I will also reject you, that you may be no priest to me. Because you have forgotten your God’s law, I will also forget your children.


    "You've got to Stand for Something or You'll fall for anything" (A. Tippin)


    Mat_15:24 But he answered, “I wasn’t sent to anyone but the lost sheep of the house of Israel.”

  13. #25
    Join Date
    Jun 2018
    Location
    Columbus, ohio
    Posts
    23
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    Registers are not dampers, shouldn’t be used as such, always at the takeoff dampers

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