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  1. #1
    Join Date
    Apr 2011
    Location
    Orlando FL
    Posts
    11

    Balancing Dampers

    Hi! I am in the process of receiving quotes on replacing one of my split systems. For this particular system, I mentioned that one of the smaller bedrooms is stuffy when the door is closed at night. After asking some questions, each of the three vendors proposed three different solutions:

    Vendor 1) Since this bedroom is the closest to the air handler, he'll install new duct work to jump directly from the supply to the room bypassing the distribution box.

    Vendor 2) He will install manual dampers in the duct work (in the attic) to balance the flow going to each of the locations handled by the distribution box. Once the dampers are set, they will be left alone.

    Vendor 3) What Vendor 2) is proposing is okay for commercial properties here in Florida, but now legal for residential properties. Is that true? I believe he said the dampers have to be motorized for a residential installation. His proposal is to put in bigger ducts for the supply in the return for the room. The grills already appear to be sized to handle the larger ducts.

    Is Vendor 3)'s comment about the legality true? Any other comments about the proposals?

    BTW, Vendor 2) will be doing a load analysis after I sign on the dotted line. Vendor 3) is working on a Manual J as part of the sales quote. Is it possible to do a load analysis that is not a full Manual J but that still meets our permitting requirements here in Florida?

    Details:
    Location is Orlando Florida
    Air handler is Carrier Infinity 58CVA110, which includes a gas furnace

    Many thanks in advance!

    Sharon

  2. #2
    Join Date
    Mar 2011
    Location
    Galveston Texas
    Posts
    530
    The reason it's stuffy at night when the door is closed is more then likely more a lack of return air rather then anything to do with supply air. Basicly what happens is with the door closed the air can not circulate. With the door closed the supply air fills the room up until it's under a positive pressure and no more can get in there. You add a return air duct so that with the door closed the air the comes in can go out and it will be able to circulate.

  3. #3
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,323

    Smile

    Quote Originally Posted by SharonG View Post
    Hi! I am in the process of receiving quotes on replacing one of my split systems. For this particular system, I mentioned that one of the smaller bedrooms is stuffy when the door is closed at night. After asking some questions, each of the three vendors proposed three different solutions:

    Vendor 1) Since this bedroom is the closest to the air handler, he'll install new duct work to jump directly from the supply to the room bypassing the distribution box.

    Vendor 2) He will install manual dampers in the duct work (in the attic) to balance the flow going to each of the locations handled by the distribution box.
    Once the dampers are set, they will be left alone.

    Vendor 3) What Vendor 2) is proposing is okay for commercial properties here in Florida, but now legal for residential properties. Is that true?

    I believe he said the dampers have to be motorized for a residential installation.
    His proposal is to put in bigger ducts for the supply in the return for the room.
    The grills already appear to be sized to handle the larger ducts.

    Is Vendor 3)'s comment about the legality true? Any other comments about the proposals?

    BTW, Vendor 2) will be doing a load analysis after I sign on the dotted line. Vendor 3) is working on a Manual J as part of the sales quote. Is it possible to do a load analysis that is not a full Manual J but that still meets our permitting requirements here in Florida?

    Details:
    Location is Orlando Florida
    Air handler is Carrier Infinity 58CVA110, which includes a gas furnace

    Many thanks in advance!

    Sharon
    I am certainly not aware of ANY Code that gets into the detail on balancing dampers that you mentioned.

    2007 Florida Residential code


    http://ecodes.cyberregs.com/cgi-exe/...ex.htm#b=M1411
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,323
    Quote Originally Posted by cuchulain View Post
    The reason it's stuffy at night when the door is closed is more then likely more a lack of return air rather then anything to do with supply air. Basicly what happens is with the door closed the air can not circulate. With the door closed the supply air fills the room up until it's under a positive pressure and no more can get in there. You add a return air duct so that with the door closed the air the comes in can go out and it will be able to circulate.
    Return air grilles for bedroom and any room with doors (study, den, library,..) were added for NEW construction
    as a FLORIDA Residential Building Code requirement in about 2006. ...
    It is highly likely that this requirement was added after SharonG's residence was permitted.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  5. #5
    Join Date
    Apr 2011
    Location
    Orlando FL
    Posts
    11
    I'm sorry...I forgot to mention that the house is about 7 years old, and yes, there is already a return in the room.

    Sharon

  6. #6
    Join Date
    Mar 2011
    Location
    Galveston Texas
    Posts
    530
    Quote Originally Posted by dan sw fl View Post
    Return air grilles for bedroom and any room with doors (study, den, library,..) were added for NEW construction
    as a FLORIDA Residential Building Code requirement in about 2006. ...
    It is highly likely that this requirement was added after SharonG's residence was permitted.
    interesting to know dan. Wish they would do something like that here. Granted we tend to shy away from new construction, except for rare occasions

  7. #7
    Join Date
    Mar 2011
    Location
    Galveston Texas
    Posts
    530
    Quote Originally Posted by SharonG View Post
    I'm sorry...I forgot to mention that the house is about 7 years old, and yes, there is already a return in the room.

    Sharon
    Is the return hooked up properly, is it large enough? Is this something new, or has it been an ongoing problem?

  8. #8
    Join Date
    Nov 2007
    Location
    Texas
    Posts
    425

    Straight forward

    I like the approach of #2. Balancing done properly should take care of your issues. Is the load calculation a room by room or block? A room by room will give the designer the information needed to ensure that the duct is properly sized to deliver the needed airflow to each room.

    Changing duct sizes or addind duct without verifying needed airflow is guesswork at best. Go with the company willing to put in the time to provide you with a measured product.

  9. #9
    Join Date
    Apr 2010
    Location
    NC Sandhills
    Posts
    411
    #2 sounds more logical, so the system can be better balanced so the room gets the correct airflow. #1 may fix one problem with another. #3 I hvae never heard manual dampers were illegal, be may mean Zoning, as (at least in NC) Zoning must use automatic dampers, but zoning one small room may be impractical.

  10. #10
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,737
    If I am picturing in my mind correctly what #1 is saying, then I like his approach.

    Make sure it'll have a balancing damper (in the new supply run) because it should increase the airflow alot.

    What is the size of the room......L x W x H ? That is the (minimum) CFM required without all the work of a load analysis.

    The problem with #2 (in my opinion) is that you'll have to choke off too much airflow to the other areas to make your room comfortable.

    Right now, I suspect that the supply to the dist. box is not able to handle the required airflow anyway. By going to the (main) supply duct, you'll notice alot more airflow to your room.

    Start there. Return could also be a problem depending on the size of the pipe or grille. You might try leaving the door open (alittle) to see if you notice an improvement.

  11. #11
    Join Date
    Apr 2012
    Location
    Louisiana
    Posts
    714
    If your only problem is with the master bedroom at night. I would go with #1. It seems like the easiest and most cost efficient way to get more air to the room considering you already have a return in the room. Definetly have a balancing damper put on the new duct. As mentioned above #2 might increase your static pressure and reduce flow to much to other rooms, unless you have sufficiently or over sized supply duct. #3 sounds alot like #1 never heard that about dampers though.

    Another thing to consider is that the thermostat may simply be set to high to keep you comfortable at night. Turing it down or adding a remote sensor in bedroom may be beneficial as well. The t-stat does not know you are hot and the unit may be cycled off.

    Edit: I just reread your post and saw this is for a smaller bedroom not the master. In that case I would not put a remote sensor and just increase the airflow to room.

  12. #12
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,357
    My eyes lasered in on "distribution box" and I thought "uh-oh"....one of those triangle shaped things with one large flex duct going in and several smaller ones going out? If so, I'm not sure dampers will help here. The overall problem could be starvation of air due to bad duct design and layout. Start dampering down on the rooms that supposedly recieve too much air (but in reality may be getting barely just enough) and although the small bedroom may improve, the problem might just shift to other areas.

    Not saying such is the case, since we haven't seen any photos of the ducts nor have the benefit of a site visit. Just wanted to put it out there as a possible snag.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  13. #13
    Join Date
    Jan 2002
    Location
    East Grand Forks, MN
    Posts
    1,373

    ??

    Quote Originally Posted by SharonG View Post
    I am in the process of receiving quotes on replacing one of my split systems. For this particular system, I mentioned that one of the smaller bedrooms is stuffy when the door is closed at night. After asking some questions, each of the three vendors proposed three different solutions:

    Vendor 1) Since this bedroom is the closest to the air handler, he'll install new duct work to jump directly from the supply to the room bypassing the distribution box.

    Vendor 2) He will install manual dampers in the duct work (in the attic) to balance the flow going to each of the locations handled by the distribution box. Once the dampers are set, they will be left alone.

    Vendor 3) His proposal is to put in bigger ducts for the supply in the return for the room. The grills already appear to be sized to handle the larger ducts.

    BTW, Vendor 2) will be doing a load analysis after I sign on the dotted line. Vendor 3) is working on a Manual J as part of the sales quote. Is it possible to do a load analysis that is not a full Manual J but that still meets our permitting requirements here in Florida?

    I'm not sure about this, but did they actually go out to your place and do some measurements and calculations? (heatload analysis, actual airflow test, static pressure and duct efficiency test).
    And how can anyone quote something like this and guarantee anything. Did they even guarantee you anything?
    Maybe I'm misunderstanding your quote above.
    Best of luck.

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