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  1. #1
    Join Date
    Dec 2007
    Location
    Sherman, Texas
    Posts
    2

    Another Homeowner needs Advice

    I'm just starting a new home.... approx 3,000 sq. ft., single story, nine foot ceilings, zoned: 3 ton & 2.5 ton Trane XL19 units. Have searched this forum, but not found anything that addresses my concern. Duct-work layout will all be hard-pipe and insulated, designed by Trane......but, is there any advantage or disadvantage to placement of the return air for the air handlers ? Get mixed answers from contractors concerning whether they should be low, wall-mounted, or located in the ceilings. Presently all are located in the ceilings, one in each bedroom and one in each hallway at opposite ends of the house. Living in N.E. Texas, my cooling season is longer than the heating season ( usually seven cooling, four heating, and one using nothing at all. This is a fantastic forum and hopefully I can arrive at a concensus of how you professionals feel about the matter. Thanks for any help that you can offer.

  2. #2
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,513
    As long as they are sized right. One in each bedroom and the others in the hallways are good. I'd keep it out of the kitchen, you'll pull cooking through the house, which is nice if the wife is cooking apple pie, but not good when she burns the ravioli. If you have great rooms,offices or media rooms, that is nice as well.

  3. #3
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,829
    Generally the return air grilles can always be put up high and in some cases down low for heating. Most contractors miss the fact that the return air needs to balance just the same way as the supplies are balanced. In other words if there's 100 CFM being put into a bedroom and there's a return air in that same bedroom (as there should be) then the return should be pulling 100 CFM to balance the supply. The reason for the return in the bedroom is so that when the bedroom door is closed, the supply air doesn't produce a positive pressure in the room, thus pushing air out through any and all air "leaks" in the room. However, if the supply is 100 CFM and the return is capable of 150 CFM, then the room will go negative pressure and suck outside air in through any and all cavities in the room envelope. Return air grilles should never be installed in a bathroom or kitchen. Most state codes forbid such locations.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  4. #4
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,633
    Designed by Trane? You must mean a Trane dealer.

    In terms of comfort, return location is mostly irrelevant. The return is a drain, nothing more. Comfort is achieved by proper supply diffuser placement, proper diffuser selection, achieving sufficient discharge velocity from the diffuser (to induce proper mixing), balanced airflow, etc.

    In terms of energy efficiency, obviously sucking in the hottest available air is preferred for AC operation.

    You've got a golden opportunity to get something that few people ever get: a properly designed system. Get that in writing. Specifically, get verification of the results as part of your contract. A Manual J calculation gives you a target to shoot for. After the installation is complete the airflow should be measured and balanced to within 10% of what Manual J calls for.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,708
    Quote Originally Posted by bmathews View Post
    I'd keep it out of the kitchen, you'll pull cooking through the house, which is nice if the wife is cooking apple pie, but not good when she burns the ravioli.
    Its against code to have a return in the kitchen or bathroom.
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  6. #6
    Join Date
    Dec 2006
    Location
    Arkansas
    Posts
    292
    As has been stated, make sure you have someone that is actually using Manual J to calculate the load for the house. It appears, unless you have excessive windows exposed west, or other possible envelope issues or special needs, that you have too much capacity (5.5 tons for 3000 sf). It all depends on your specific situation, so it may be ok. I would find out if they did a calculation, and some details about it.

    The next step is selecting the equipment to match the load (Manual S). Then your ductwork comes into play (Manual D). This should include balancing dampers. As for the return, the size is more important than location. Most installations have a restricted return grille which in turn can cause the refrigerant charge to be incorrect and the overall system to operate inefficiently. If all of that is done correctly, you should use Manual T guidance and select the correct supply grilles to distribute the air correctly. And lastly, as has been mentioned, balance the system to get the correct amount of air defined by the load calc.

  7. #7
    Join Date
    Dec 2007
    Location
    Sherman, Texas
    Posts
    2

    Thanks

    Thanks very much for the responses offered by all. I feel more confident now. The house has had a Manual J calculation, and all diffusers will have dampers in-line, for balancing. The rear side of the house includes more than average glass exposure (lots of forest to view), so that accounts for the small increase in HVAC capacity. If, by any means, anyone thinks of other
    suggestions that might provide increased efficiency, please continue to help me. Thanks, again.

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