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  1. #1

    5 ton coil , what size return would you recommend

    If you have a 5 ton coil what size return would you install to make sure there was enough return air?

  2. #2
    Join Date
    Oct 2011
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    NJ
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    You haven't given enough information about your system to make a good recommendation. Is the supply ducted, if so what is the duct system like? What is the external static pressure available on your fan? What is the CFM rating that the system is designed for? Are you putting in multiple return air openings or just one? Do you need to duct the return?

    A common 5 ton system would be 2000 CFM (400 CFM per ton) so a 24x30 register or grill (-.02" sp) with (10) feet of 24x12 duct (-.092"/100') with a duct transition to the RA opening of the unit (if duct is needed) would be a fairly low loss system.

  3. #3
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    Nov 2010
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    cali
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    2 30x20 this will be 2400 cfm and will be very effective and quiet with a 18 in duct for each can. There is no other way to accomplish the air flow with a single return air can for a five ton unit, even though guys out there always use a single can with one 18 in. Duct. Which is completely undersized. These measurement are according to national comfort institute charts.. Good luck with your design and install.

  4. #4
    Join Date
    Oct 2011
    Location
    NJ
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    HVAC_Husker, I was using a straight deflection grille, which is good for 2465 CFM at -.03 sp. You are right for an angled deflection grille, 2 are needed. One 30x24 is good for about 1610 at -.03 using an angled deflection grille.

    In a commercial setting there should be outside air to the unit so with 10% OA, 2000 CFM would be a more likely CFM for 5 tons.

    However, if there is no outside air or a dedicated OA system, then 2400 is good.

    As I said, there isn't enough information to make a good recommendation.

  5. #5
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    Nov 2010
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    cali
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    I totally agree with you if your bringin in fresh air.. but a 5 ton system needs a 22in. Duct for proper cfm 20 in is just short of 2000 cfms. Im sure it will work with what your saying but I have been through the training with nci air.balancing and im stickin with the informatiin I originally posted..

  6. #6
    Join Date
    Oct 2011
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    NJ
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    Quote Originally Posted by HVAC_HUSKER View Post
    I totally agree with you if your bringin in fresh air.. but a 5 ton system needs a 22in. Duct for proper cfm 20 in is just short of 2000 cfms. Im sure it will work with what your saying but I have been through the training with nci air.balancing and im stickin with the informatiin I originally posted..
    Are you talking flex duct? If so, I agree because flex duct has higher static losses. I was talking unlined metal duct. I almost always design using metal duct for RA with minimal flex to the unit and hard connected to the register.

  7. #7
    Join Date
    Nov 2010
    Location
    cali
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    Ya I was thinking flex, when I hear five ton to me thats residential I.know they have them on commercial applications but I always run flex in residential.. ya the rigid definitley has less static..

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