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  1. #53
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    Apr 2008
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    Quote Originally Posted by beenthere View Post
    Once you get the supply static down, your return static could go up, as the blower will be able to move more air against the lowered supply static.
    have the supply fixed first, then retest your return, and see if you need to fix it.
    I thought that "one could not have too much return air"?

    Since I'm having the return drop pulled out anyway to add a 5" media cabinent (which is actually 7-10 inches).....I thought I would at the same time increase the return.

    At my high static I need every 0.1 inch I can get...

    Key1

  2. #54
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    Jan 2004
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    Lancaster PA
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    You sounded like you didn't really want to spend the money on the return. I just offered away to check, and decide if its worth it to you.

    I think you'll find it increases after the supply is lowered. I just present the options.

    I never said don't increase it.
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  3. #55
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    Princeton, NJ
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    Quote Originally Posted by beenthere View Post
    You sounded like you didn't really want to spend the money on the return. I just offered away to check, and decide if its worth it to you.

    I think you'll find it increases after the supply is lowered. I just present the options.

    I never said don't increase it.
    Thanks....

    I hope your suggestion of "helper ducts" does the trick. Once the helper duct (or 2 or 3) are attached to the plenum and then reconnected to the trucklines further down where I want air to flow, does it make a difference if they are reconnected 5 ft from the furnace compared to 10 ft away?

    Also, would one 12 inch round helper duct line off the backside of the plenum provide the same reduction in static as two 6" round helper duct lines?

    Key1


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  4. #56
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    To an extent, the further from the furnace the better.

    Bad rule of thumb. 2-6"=1-8", 2-8"=1-10", 2-10">1-12"
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  5. #57
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    Apr 2008
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    Quote Originally Posted by beenthere View Post
    To an extent, the further from the furnace the better.

    Bad rule of thumb. 2-6"=1-8", 2-8"=1-10", 2-10">1-12"
    Wow!

    One 12" round will reduce the static better than two 10" round?

    Does the 12" round work better than a 12x8 rectangular??

  6. #58
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    I'm pretty sure that a used a greater than sign infront of the 12.
    2-10" flow a bit more then one 12".

    A 12" round moves more air then a 12 x 8.
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  7. #59
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    Princeton, NJ
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    Quote Originally Posted by beenthere View Post
    I'm pretty sure that a used a greater than sign infront of the 12.
    2-10" flow a bit more then one 12".

    A 12" round moves more air then a 12 x 8.
    ooops.
    you're right.

    Thanks

  8. #60
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    Quote Originally Posted by beenthere View Post

    A 12" round moves more air then a 12 x 8.
    Got it!

    Does reducing the 12" round to an 8" round 10 ft away from the furnace to to tie it into an (8" x 12 trunk) mean that the static reduction I could expect would be the same as if I had an 8" round the entire distance?
    Key1

  9. #61
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    Depending how he can run it, yea about the same amount of air. 12" could allow a little more, depending on how its tapped into the plenum.
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  10. #62
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    Quote Originally Posted by beenthere View Post
    Depending how he can run it, yea about the same amount of air. 12" could allow a little more, depending on how its tapped into the plenum.
    I need as much air as possible to get the static down so I'm thinking of having him pull two 8 inchers off the 12", 10ft from the furnace and tie both into the the trunk.

    Would that help?

    Key1

  11. #63
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    It should. you can do a static test on the duct to see where it drops off at, to know where to tap them in at.
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  12. #64
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    Quote Originally Posted by beenthere View Post
    It should. you can do a static test on the duct to see where it drops off at, to know where to tap them in at.
    To obtain the desired temperatures upstairs and down stairs the damper on the front trunk line had to be closed (it leads to the closed off laundry area and the unsealed garage .

    After other dampers were nicely balanced to get the entire house comfortable and uniform..... this caused my high static of .79 supply and .3 return.

    The back supply trunk line off the plenum now has pressure of 0.4 and the side supply trunk line off the plenum has a pressure of 0.37 when measured at 5 ft, 9ft, or 15 ft from the furnace (it did not change with distance).

    Hopefully the tech that comes this afternoon is as smart as you guys....

    I was reading Udarrels site but I still don't quite understand how adding the helper ducts off the plenum is going to reduce the TESP if I am not increasing grill sizes at registers and not adding any new registers??

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  13. #65
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    What is the static in the plenum above the coil.

    A helper duct only works if the duct it to help is losing pressure.
    Sometimes the ducts attachment to the plenum is the problem. Your may not be.
    With the balancing dampers closed/choked down to first floor supplies you are increasing the static in the duct because the air flow is now slowed down in the trunk line.

    The trunks static is best checked with all of its dampers open. To know how well it is carring the air. A full load test.
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