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Thread: Damper question

  1. #1
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    Damper question

    A tech last week recommend that I have some dampers installed in my ductwork in order to properly balance the air flow in the house. There are two duct runs from the air handler. It is as follows:

    1. First duct run (flex) ends in a distribution box with five flex ducts stemming from it. Two of the flex ducts go to the master bedroom, another duct runs to the water closet in the master bedroom, the other duct runs to the master bedroom, and the last one goes to the closet in the master bedroom. This master suite (Which the air handler is located right above) gets too cold and too hot (in summer and winter) relative to the house. This is particularly where I would like to have dampers installed. Currently, we have one register completely closed in the bedroom, and both closet registers completely closed (one in the water closet and regular closet). In other words, we only have two of the five vents open and that provides enough air. Does having too many dampers (reducing air flow) hurt our air conditioning system? Ideally, I would like to have dampers on all five of these ducts and completely shut off the closets and reduce air flow the rest of the vents. Would this be OK or will it hurt my system? I hope this would push air throughout the rest of the house more efficiently.

    2. Second duct run (flex) goes to one distribution box with five runs, at the end of the box, more flex duct runs to another box with five runs, and finally more flex runs to a third box.

    I had a tech at my house last week and he said the ductwork design is poor. He recommened dampers to help with the balancing. What do you think? Could I just have them installed on the individual duct runs that go to the master bedroom and bathroom?

    some stats on the house. 3 ton air conditioner (Comfortmaker), roughly 1,500SF house located near Greensboro, NC. system was installed brand new in 1996. Recently was serviced and had one pound of freon added to the system.

    Thanks for your help in advance!

  2. #2
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    How many returns do you have and where are they located? Do you keep the doors open or closed in the problem areas? Did the tech test your system for proper amount of air flow for the size of your unit? Reducing air flow will hurt the system unless it's variable speed and designed for that function.

  3. #3
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    How about some pictures of that marvelous ductwork? I'm sure it will stir up much discussion!

    With the magnitude of problems you are describing, it's about a sure thing there was little to no effort to determine how much air each room was supposed to receive. Throwing up a bunch of flex duct and hoping for the best sounds to be about the extent of duct design applied toward your system. This is all too sadly repeated ad naseum, since air distribution is likely the least understood aspect of the HVAC trade.

    Dampers in your case are probably nothing more than band-aids, and tepid ones at that. A proper duct design and installation will put you dollars and comfort ahead of where you are now.

  4. #4
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    Quote Originally Posted by shophound View Post
    How about some pictures of that marvelous ductwork? I'm sure it will stir up much discussion!

    With the magnitude of problems you are describing, it's about a sure thing there was little to no effort to determine how much air each room was supposed to receive. Throwing up a bunch of flex duct and hoping for the best sounds to be about the extent of duct design applied toward your system. This is all too sadly repeated ad naseum, since air distribution is likely the least understood aspect of the HVAC trade.

    Dampers in your case are probably nothing more than band-aids, and tepid ones at that. A proper duct design and installation will put you dollars and comfort ahead of where you are now.
    well said.


    And now for my two cents. System is 13 years old. Plan on replacement in the near future. Especially since you claim "freon" was added.

    And when you replace. The replace with a high efficiency system and all new ductwork that is properly sized for the system as well as a good balance of air distribution.
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  5. #5
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    Quote Originally Posted by iraqveteran View Post
    well said.


    And now for my two cents. System is 13 years old. Plan on replacement in the near future. Especially since you claim "freon" was added.

    And when you replace. The replace with a high efficiency system and all new ductwork that is properly sized for the system as well as a good balance of air distribution.
    Yes, you'll never balance that flextopus, waste of time trying IMO.
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  6. #6
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    Quote Originally Posted by shophound View Post
    How about some pictures of that marvelous ductwork? I'm sure it will stir up much discussion!

    With the magnitude of problems you are describing, it's about a sure thing there was little to no effort to determine how much air each room was supposed to receive. Throwing up a bunch of flex duct and hoping for the best sounds to be about the extent of duct design applied toward your system. This is all too sadly repeated ad naseum, since air distribution is likely the least understood aspect of the HVAC trade.

    Dampers in your case are probably nothing more than band-aids, and tepid ones at that. A proper duct design and installation will put you dollars and comfort ahead of where you are now.
    Attached are some pictures of the flexopus. I am very interested in your comments. If you need to see anything more, let me know and I can take some more pics.

    The tech told me the cost of new ductwork is typically half the cost of total new system install. That's pretty expensive to me, but I guess I have to do what I have to do. What do you guys think? The smaller duct (on the left) is what goes to the master bedroom and master bathroom. The larger duct, feeds the entire rest of the house (two bedrooms, a living room, a sunroom, kitchen, dining room, and front entry way). Does the large duct look like it is crimped by the truss?

    I greatly appreciate your comments, good or bad. I'd love hear what the pros think.
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  7. #7
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    Quote Originally Posted by big johnson View Post
    How many returns do you have and where are they located? Do you keep the doors open or closed in the problem areas? Did the tech test your system for proper amount of air flow for the size of your unit? Reducing air flow will hurt the system unless it's variable speed and designed for that function.
    I have two returns. One is a 12x12 located in the hallway near the master bedroom and master bath (with the excess air flow). The second return is a 20x20 on the other side of the house. Filters are changed every month and I always make sure the outdoor is clear of any debris.

    The tech did not measure the air flow. Apparently, he did not have the tools to do that. I'm a new homeowner and feel clueless when it comes to HVAC related matters.

    Your comment about reduced airflow hurting the system concerns me. As I mentioned earlier, I would really like to put dampers on the five flex runs in the master bedroom and bath, but I am afraid I'll do major damage to the system. Plus, I would have to pay someone to install the dampers if it really won't solve the problem. It's just frustrating all over unfortunately.

  8. #8
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    A tech not having the tools to measure air flow scares me. Like others have stated, throwing in dampers is not the answer. You have to start from square one. What's the design cfm of the unit and is your ducting sized to handle it? Before you start throwing money at modifications, you need a good evaluation of your system and your living space. That can also be costly but it will be money well spent. You're off to a good start seeking information and now you have to research an HVAC contractor in your area that can do the job properly.

  9. #9
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    Looks like most of your flex wasn't stretched when it was put in. The flex on the top of the supply plenum is making a 110° turn and restricting because its not supported.
    The flex attached to the top of the return plenum looks to have the same problem.
    Poor install methods.
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  10. #10
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    As said, I don't think that duct system will work no matter what you do to it. Very sloppy install. As said above you should call around and find a company that can evaluate the system and give you the best options on replacing it.

    What are the model numbers of the furnace and air conditioner?
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  11. #11
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    Your pic's look pretty typical to me. Not perfect, but typical.

    Your system is 12 years old and 1 pound of refrigerant was added. Could have been a bit less, but the tech would still have listed it as one pound. I do. If the coils weren't cleaned (if needed), it may not have needed any. Regular service over a 12 year period could also result in having to add that pound. It's no biggie.

    Have your tech install the dampers and balance your system for now as best he can. They should have been installed when the unit was put in, but most contractors pinch pennies and don't do it.

    Replacing the ductwork on your system is a waste of money. (JMO) My guess is that when a new system is needed and a proper load calculation is done you will find that you are oversized and need a smaller unit. If so, the ductwork could need replacing again.

    I think your best bet is to go with your tech's reccomendation (dampers) and start saving for a total system (unit and ductwork) replacement sometime in the next 8 years. Course if you have money to burn, you could go ahead and replace it all now. I woulden't.

  12. #12
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    You stated that the tech didn't have the tools to measure airflow, yet he wants to install dampers and balance your system. How!! Using his hands to see how much air is being ditributed to each room. He may have good intentions, but not the capacity to do it the right way. Call someone else. Try National Comfort Institute. http://www.nationalcomfortinstitute.com/

    Good luck
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  13. #13
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    OP stated that tech didn't measure airflow so it was ASSUMED he didn't have the tools. We all know what assume is so lay off the tech please. The fact is most tech's don't measure it if they don't feel it is necessary. Nothing to do with what equipment they have in their arsenal.

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