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Thread: Return Location

  1. #1
    Join Date
    Mar 2004
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    171
    We have a new 2-story house under construction right now, and it appears that the HVAC contractor is putting one large return for the upstairs HVAC system (separate system), which covers 1300 square feet, in the upstairs hallway. The floors will be all hardwood, and there will be gaps under the bedroom doors (4 bedrooms upstairs) with the doors closed.

    Is it better to have a separate return in each room, or will one large one in the hallway suffice, provided there is enough airflow under the doors, or if the doors are left open. If returns are placed in the individual rooms, is there a best location for them? The ducts are all run through the ceiling. If returns are in the ceiling as well, should they be spaced a minimum distance from the ducts?

    Thanks.

  2. #2
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
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    2,965
    Returns in every room except baths and kitchens are best.

    Return should be on opposite side of room from supply.

    You should also expect to pay more if you go this route because there will be more materials and labor needed to do the extra work.

    The "central return" concept works well also, just not as good as a return in every room.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    1.) It's cosidered somewhat better to have a return in each room,other then baths and kidtens.

    2.)Gaps under the door ,IF large enough ,will work.The gap maybe much larger then you would like.

    The gap under the door provides a "return path".This can also be an openining in the wall between the BR and hall,with a grille on each side.Another way is a large grille in the hallway,with ducts to each BR with a grille.Either of these requires a much larger opening and duct then the supply grille feeding the room.

    3.)Return location high or low,has little effect on comfort.If the supply is on a west wall in the center of the room,return on the same wall near the corner will give you the best air mix.

    See Manual D and t From www,acca.org






  4. #4
    Join Date
    Mar 2004
    Posts
    171
    Thanks for your replies. I was reading the document linked below put out by the Department of Energy, and it says that "undercutting doors to provide 1 inch of clearance to the floor is usually not sufficient by itself". http://www.eere.energy.gov/consumer/.../mytopic=12730 How large should the gap be? I tried to look up Manual D on http://www.acca.org, and could not locate any info.

    I'm concerned the HVAC contractor is cheaping out on me. He previously tried to substitute Goodman equipment for my Rheem Modulating furnaces I spec'd out, and I told him no way. We are getting close to having to sheetrock. Should I insist on jumper ducts as suggested by dash in #2 below? Or would transfer grills whown in the link above for the department of energy work OK?

    [Edited by bydabeach on 07-18-2006 at 07:25 PM]

  5. #5
    Join Date
    Jul 2006
    Location
    Northern Ohio
    Posts
    4
    Based on a standard 32" door. A gap of 1" will give you 32 square inches of return. Compared to a standard 14x6" return air grille that allows 75% "free area" that gives you 63 square inches. By doing the math alone, a separate return in each room will double the return capacity; everything being equal of course.

    Years (and I'm talking YEARS) ago, returns weren't necessaily installed on the second floor. The thinking was that most of the time, the bedroom doors are open during the day and they could use the stairwell as a return.

    I don't know how many rooms you have upstairs, but if it's more than two standard size rooms, a "double" return still may not be enough. Besides, having a single return was probably just a way for the contractor to keep his costs down to be awarded a job.

    All in all, everyone buys their supplies from the same suppliers, receive the same prices. The same goes for equipment although some equipment is substantially less expensive than others (because of quality of construction). With that being said, what makes the difference in price? Besides profit levels that is. It's labor...which in most cases is the most expensive commodity. The faster they complete one job, the sooner they can start another and reap the benefits of markups on more equipment.

  6. #6
    Join Date
    Feb 2005
    Posts
    249
    Originally posted by metalguy
    Based on a standard 32" door. A gap of 1" will give you 32 square inches of return. Compared to a standard 14x6" return air grille that allows 75% "free area" that gives you 63 square inches. By doing the math alone, a separate return in each room will double the return capacity; everything being equal of course.

    Years (and I'm talking YEARS) ago, returns weren't necessaily installed on the second floor. The thinking was that most of the time, the bedroom doors are open during the day and they could use the stairwell as a return.

    I don't know how many rooms you have upstairs, but if it's more than two standard size rooms, a "double" return still may not be enough. Besides, having a single return was probably just a way for the contractor to keep his costs down to be awarded a job.

    All in all, everyone buys their supplies from the same suppliers, receive the same prices. The same goes for equipment although some equipment is substantially less expensive than others (because of quality of construction). With that being said, what makes the difference in price? Besides profit levels that is. It's labor...which in most cases is the most expensive commodity. The faster they complete one job, the sooner they can start another and reap the benefits of markups on more equipment.
    The difference in a return and a gap under the door,is more then you indicate.A ducted return has the static pressure of the ducts to move air,under the door ,thru the wall or jumper has no sts\atic to move air and needs to be much larger then a ducted return,but will work perfectly if sized correctly.

  7. #7
    Join Date
    Mar 2004
    Posts
    171
    I've read a bunch of articles on the Building Science website, and I'm starting to think I'm getting hosed on my install. Where would I even start to discuss this with my contractor? Ask for the manual D calculations and the airflow in each room to ensure I have adequate returns?

  8. #8
    Join Date
    Jun 2006
    Location
    Richmond, VA
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    2,672
    Are you the builder or just the person buying the house? if you are using a builder, one return is probably what was spec-ed to be competitive with the other 10 hvac contractors in the area. If you are the builder, what specs did you give your hvac sub? A comfort system designed right is an option. (A single return is a design that requires your bedroom doors to be open to work properly.) Multi returns are an option. Gaps under doors does not work unless you make them big. Jumper ducts or grills work second best, the absolute best are returns. And it does cost more....returns cost more because of size and are the first corners cut.
    It's not the Brand with the fewest repairs-It's all in the install!!! Attention to detail and using the best materials!

  9. #9
    Join Date
    Mar 2004
    Posts
    171
    I am having the house built. Having spec'd a high end system with a Rheem modulating furnace, I assumed that corners would not be cut elsewhere. I made it pretty clear that the HVAC system was important to me. In the bid phase, it's very difficult to spec every detail of every aspect of the job for the electrical, plumbing and HVAC, and there are certain things you assume when you are building a higher end custom house. I obviously assumed too much.

    What should I specifically ask the builder on the size of the gaps under the door and the need for tranfer grills or jumper ducts? I don't want 4 inch gaps under the door to get the proper air flow. There are 4 bedrooms upstairs. Two bedrooms are 170 square feet each, one is 120 square feet, and the master suite is about 450 square feet (bedroom is 250-300 square feet plus bathroom and dressing area). When I asked about the central return a couple of weeks ago, the builder told me it was "fine" the way it was.

    I am more interested in having the HVAC system done right rather than taking the cheap and easy way out, and if I have to cough up more money, than so be it.

  10. #10
    Join Date
    Mar 2006
    Location
    The South
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    bydabeach

    You should be aware that supply air and return air must be in balance. It is obvious that you are not going to be happy with a central return. Tell your dealer promptly that you want individual room returns sized correctly. Individual returns are better for good airflow exchange especially if you want to close the doors.

    My opinion.

  11. #11
    Join Date
    Jul 2005
    Posts
    717
    Originally posted by tigerdunes
    bydabeach

    You should be aware that supply air and return air must be in balance. It is obvious that you are not going to be happy with a central return. Tell your dealer promptly that you want individual room returns sized correctly. Individual returns are better for good airflow exchange especially if you want to close the doors.

    My opinion.
    ***********************************************
    very good advice, and I completely agree.

  12. #12
    Join Date
    Mar 2004
    Posts
    171
    Thanks for the advice, and I'll ask.

    On the downstairs, the floor plan is open and it is only about 1000-1100 square feet. There are no doors between any of the rooms, and I don't have a problem with a central return for the downstairs. The downstairs is probably OK, correct?

  13. #13
    Join Date
    Jun 2006
    Location
    Richmond, VA
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    That's fine as long as the return is sized correctly.
    It's not the Brand with the fewest repairs-It's all in the install!!! Attention to detail and using the best materials!

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