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  1. #1
    Join Date
    Oct 2006
    Posts
    24

    What causes one vent to be stronger than others?

    Hello, I was looking for some help. We have a 3 ton HVAC unit with 5 ducts sending air. Two of them are 8", 2 are 6" and the last one is a 4".

    The situation is that all of them are fairly quiet and smooth operating, but one of the 6" supply registers seem to be much stronger in terms of air coming out but also, this translates to this one being much louder than the others.

    The 4" is actually the most quiet one as you can barely hear anything coming out of it. Consequently, it's also the least forceful when it comes to air coming out.

    Does anyone have any thoughts or advice on how we can reduce the amount of air coming out of this supply and also to reduce the noise? All the ducts are flexible ducts but I do think this one tends to have some bends and turns which unfortunately is unavoidable.

    Thank you in advance for any insight!

  2. #2
    Join Date
    Feb 2007
    Location
    va
    Posts
    23
    how many supply vents on this 3 ton setup?

    the duct you mentioned, is that all the supply duct?

    installing a dampered collar on the 6in run will let you adjust airflow.


    vaughn

  3. #3
    Join Date
    Jan 2007
    Posts
    332
    Sounds like you might need some duct dampers to properly balance airflow to each room. If you already have dampers then a service tech should come out with the proper equipment and balance each register. You could also have a harmonics problem where the velocity of the air flowing out of the register causes a whistling type noise. To check for this remove register and see if noise goes away, if it does then you have a harmonics problem. A 4" supply is very small and in my opinion should not be used in HVAC. A 6" supply is the smallest I'll use. You may have it changed to a 6" to increase volume. Suggest just having a pro come out and assess your situation since it is very difficult to do on here without seeing system.
    Believe none of what you hear and half of what you see.

  4. #4
    Join Date
    Oct 2006
    Posts
    24
    Thank you both for your suggestions. You're both correct as I know there aren't any dampers in any of the ducts.

    We have 5 supply registers in total and none of them have anything in terms of air control. Yes, I'll be sure to put one in.

    Regarding the register itself, I do think it is a harmonics problem as when I remove the register, it sounds much better.

    So perhaps I could change the type of register?

    Also, when I add dampers to the supply, would it change the dynamics of the system where it would be working harder than before? And finally, would adding the damper increase possible noise in other supplys?

    Thank you all again.

  5. #5
    Join Date
    Feb 2007
    Location
    va
    Posts
    23
    5 supply vents total! on a 3 ton setup!! how big is the house/area that is being conditioned?

    sounds like way too big a system for 5 vents! run system in low speed and add some vents!


    vaughn

  6. #6
    Join Date
    Oct 2006
    Posts
    24
    I think you're right as I imagined it was too big also. The basement and the first floor that it is cooling/heating is only about 1400 sq ft. in total.

    I think I'll add a damper but also reduce the fan speed. I think I can wire it based on the furnace panel detail on running it on low speed but I'll also be aware of the temperature rise with the change.

    Finally, any thoughts on a better register box as the one I'm using does seem to be loud.

    Thank you all again.

  7. #7
    Join Date
    Feb 2007
    Location
    va
    Posts
    23
    it's loud because there is too much airflow for 5 vents. add about 5-7 more vents and adjust fan speed. install return duct on both floors.


    vaughn

  8. #8
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    This setup needs to be looked over by a professional.

    I can guarantee the duct setup is wrong and you will be having mechanical failures with your system in the near future...

    Who put such a large system on that small a duct system?

  9. #9
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by gemajean View Post
    I think you're right as I imagined it was too big also. The basement and the first floor that it is cooling/heating is only about 1400 sq ft. in total.

    I think I'll add a damper but also reduce the fan speed. I think I can wire it based on the furnace panel detail on running it on low speed but I'll also be aware of the temperature rise with the change.

    Finally, any thoughts on a better register box as the one I'm using does seem to be loud.

    Thank you all again.
    Your duct system sounds like it's severely undersized.

    What duct size/length is used for the return??

    I would look at getting it sized properly,larger ducts or more ducts,whatever fits the home the best.Or if the system is oversized ,get the right size system as it night be the right size for your duct system.

    What is the temperature rise now?

  10. #10
    Join Date
    Oct 2006
    Posts
    24
    Thank you all for your advice.

    Yes, there definately seems to be too little venting, especially since one of them is a 4" supply! I wish I knew more about this before.

    Unfortunately I've tried the people who put the system but they are no longer in business (how surprising right?)

    But I do know that when they put the system in, there were many obstacles to overcome such as wall and construction limitations and they did what they thought was best but I always had a feeling that perhaps they didn't think about it thoroughly enough.

    In any event, I think I'll have another tech come in and analyze but for now, I'm thinking of doing your suggestions of adding more vents and lowering the blower speed.

    I haven't done that yet so I don't have the measurement of the temperature rise as of now but will shortly.

    Finally, in regards to adding more vents, would it be ok to add vents by installing tees or y's in the existing vents and run the vents from there or should they be created at the trunk and plenum area?

    Thanks again for any advice!

  11. #11
    Join Date
    May 2006
    Location
    Texas
    Posts
    537
    Quote Originally Posted by gemajean View Post
    Finally, in regards to adding more vents, would it be ok to add vents by installing tees or y's in the existing vents and run the vents from there or should they be created at the trunk and plenum area?

    Thanks again for any advice!
    You need someone to come out who is well read with manual D, duct design, who can evaluate and correct your issues. Anything less and you are wasting your time and creating potential harm to your system.

  12. #12
    Join Date
    Oct 2006
    Posts
    24
    Thank you for your response. I wasn't aware of Manual D and it's impressive to see this software.

    Yes, I'll look for someone who has this expertise. I'm located in New York city. Any recommendations?

    Thank you again.

  13. #13
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Gotham

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