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Thread: 6inch to small?

  1. #14
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,248
    Originally posted by brianshouse
    All the beach houses here use flex duct but they do not pull flex through the webs, they have enough room to run the supply trunk in the center of the truss, and then the flew is run beside the trusses.

    Somehow my trusses where engineered different and my space is too small so I will have to run the supply trunk differently.

    My parents have the same stle house and their 3 ton system just doesn't do it with the cathedral ceilings, thats why I'm going with 3.5 ton.
    What is the total AHU air flow in your parents house?
    What is the deltaT across the coil?
    i.e. 75'F room temp, 56'F at coil outlet ?

    What is the S.A. temp at the AHI outlet and at the diffuser?

    ++++++++++++++++++++
    Use R-20 spray foam, THEN 2.5-Ton unit mounted in conditioned space may be sufficient.
    +++++++++++++++++
    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

  2. #15
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by brianshouse
    All the beach houses here use flex duct but they do not pull flex through the webs, they have enough room to run the supply trunk in the center of the truss, and then the flew is run beside the trusses. Somehow my trusses where engineered different and my space is too small so I will have to run the supply trunk differently. I have seen the trunk under the trusses and it was boxed in later. I don't plan on spending thousands of dollars on a job that wouldn't take hours to do. I want plenty of tape and mastic with no leaks, It is hard to not find a jackleg around here. My parents have the same stle house and their 3 ton system just doesn't do it with the cathedral ceilings, thats why I'm going with 3.5 ton.
    With supply grilles in the floor .Manual d is critical,the need to push the cold air well above the occupants,ie >7'.

    An undersized duct system won't do this and adding a half a ton won't correct the problem,in fact it could make it worse.


    How's the air flow at your parents house??

    Manual J,S and D,and you'll be fine.

  3. #16
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    5,443
    Brian

    How old is your parent’s house, what size, How many windows, what direction is it facing? Where is it located? These are just some of the questions we need to correctly size this system.
    Around here the mice Love flex duct to gain access in the winter!

    You’ve haven’t mentioned heating, so I assume it will be shut down in the winter.

    Check out http://www.mrslim.com and look at there MXZ unit. 3 indoor units, 1 outdoor. Heat / Cool & Dehumidification.

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