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  1. #105
    Join Date
    Jul 2006
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    Southern Ca, Elkton Md
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    7,572
    Quote Originally Posted by Brian GC View Post
    I never improved my dual two story system I described earlier. Rerouting an upstairs ceiling return to downstairs is next to impossible. But, I tested and fixed other one story houses with amazing results. I will outline them in a later post.

    I know we have beaten this subject up partly on an account of my personal interest, so I thank you, and other, for hanging in there. But one more question--- your last statement said “change in return is unnecessary if the system had been designed properly”. So, you do recognize that a “change in return” (lowering) can be beneficial to a heating system? Then, if lowering a return can “heal’ the ills of a poorly ducted supply system, then why wouldn’t it be as, or more, beneficial to a properly ducted system?

    BTW – Sorry for being a little testy earlier. The engineers I referred to each had ten years of education plus twenty years of experience in their fields. One was even a Licensed Engineering Contractor who operates and re-builds oil refineries…a level few of us ever achieve. So, heat flow, loss, stratification, and convective properties were right up his alley.

    Brian
    Moving the return was a band-aid, and it improved, but it did not correct the improperly designed duct system.
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  2. #106
    Join Date
    Mar 2008
    Location
    Long Beach, CA
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    3,731
    Quote Originally Posted by shophound View Post
    In your case, just shooting off the cuff I'd say the design error of using an upstairs return for a downstairs zone is plain. A "cold floor" is not only indicative of insufficient air exchange (stagnation), it also can indicate infiltration due to stack effect (wanna bet every ceiling penetration upstairs in your home is NOT sealed?) and, if outdoor ground temperatures drop low enough, a cold slab foundation for slab on grade homes. Single pane windows and sliding glass doors that are thermally poor also contribute to chilly feet syndrome.


    Shophound,
    The reason one of the downstairs returns in my house is upstairs is the main reason all ceiling returns are used, they are easier to install that way!

    As to your bet, there are only ten IC ‘airtight’ recessed lights upstairs with no other ceiling penetrations. Attic access is tight and in a closet. The rest of the house is only 6 years old with vinyl dual pane throughout, q-lon doorways, and hardwood floors on slab. Exterior rarely goes below 50 degrees. No leaks.

    My friend has a house with the return 25 feet high in a cathedral ceiling. His heater does not heat the house. He has given up on it and has resorted to a small electric space heater. What a shame because he just had to replace his fifteen year old heater because of manufacturer defects. The new one does not work either because of return placement. I am tempted to rip his walls and closets open to bring the return to the floor, but it is a lot of work. He is an engineer too and understands what is going on. He wants to shoot the GC, architect, and HVAC contractor (like many others would want to do if they were in the know).

    Brian

  3. #107
    Join Date
    Mar 2008
    Location
    Long Beach, CA
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    3,731
    Quote Originally Posted by weber View Post
    Moving the return was a band-aid, and it improved, but it did not correct the improperly designed duct system.
    Weber,
    It has not been determined the supply ductwork is improperly designed, it is only assumed. Moreover, “properly designed supply duct systems" and ceiling fans may just as well be a bandage for not having a low return, since low returns fix the problem just as well, maybe better.

    BTW – Respectfully, You did not answer the question.

    Brian
    Last edited by Brian GC; 03-21-2008 at 04:17 AM. Reason: added info

  4. #108
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,189
    Quote Originally Posted by Brian GC View Post
    I never improved my dual two story system I described earlier. Rerouting an upstairs ceiling return to downstairs is next to impossible. But, I tested and fixed other one story houses with amazing results. I will outline them in a later post.

    I know we have beaten this subject up partly on an account of my personal interest, so I thank you, and other, for hanging in there. But one more question--- your last statement said “change in return is unnecessary if the system had been designed properly”. So, you do recognize that a “change in return” (lowering) can be beneficial to a heating system? Then, if lowering a return can “heal’ the ills of a poorly ducted supply system, then why wouldn’t it be as, or more, beneficial to a properly ducted system?

    BTW – Sorry for being a little testy earlier. The engineers I referred to each had ten years of education plus twenty years of experience in their fields. One was even a Licensed Engineering Contractor who operates and re-builds oil refineries…a level few of us ever achieve. So, heat flow, loss, stratification, and convective properties were right up his alley.

    Brian
    Buy this book. They've done the field testing to show that returns are irrelevant when supplies are correct.

    You got lucky on your choice of engineers. There are engineers that work in this field that don't grasp the concepts we are discussing.
    Perhaps you should have read the instructions before calling.

  5. #109
    Join Date
    Apr 2002
    Posts
    11,808
    can tell spring has sprung, ducks are flying north, can hear them quacking

  6. #110
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    18,836
    Quote Originally Posted by Brian GC View Post
    I never improved my dual two story system I described earlier. Rerouting an upstairs ceiling return to downstairs is next to impossible. But, I tested and fixed other one story houses with amazing results. I will outline them in a later post.

    I know we have beaten this subject up partly on an account of my personal interest, so I thank you, and other, for hanging in there. But one more question--- your last statement said “change in return is unnecessary if the system had been designed properly”. So, you do recognize that a “change in return” (lowering) can be beneficial to a heating system? Then, if lowering a return can “heal’ the ills of a poorly ducted supply system, then why wouldn’t it be as, or more, beneficial to a properly ducted system?

    BTW – Sorry for being a little testy earlier. The engineers I referred to each had ten years of education plus twenty years of experience in their fields. One was even a Licensed Engineering Contractor who operates and re-builds oil refineries…a level few of us ever achieve. So, heat flow, loss, stratification, and convective properties were right up his alley.

    Brian
    100 cfm from a properly designed supply can cause 10 to 20 times that cfm in air movemnet,much of it below 75 feet per minute.You always feel some movement several feet away.

    How far away from a return do you feel movement?

    Do you believe the lw return can pull air from the far side ,or even the middle of the room??

  7. #111
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    Mar 2008
    Location
    Long Beach, CA
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    3,731
    Quote Originally Posted by dash View Post

    Do you believe the lw return can pull air from the far side ,or even the middle of the room??
    Without a doubt. In the same way heat (or smoke) will spread across the entire ceiling, cold air will spread across the entire floor. If a return is down there constantly sucking it out that stratum will eventually be evacuated and replaced by the ever accumulating upper heated strata. This is exactly how a wall furnace, a baseboard heater, a floor mounted heater, and a fireplace works. They produce absolutely no air circulation at all and work just fine. This basic heating principal has not only been abandoned, but it has been reversed with ceiling mounted returns. And, if this principal was used with FAV heaters, you'd have a properly designed system, irrespective of supply throw, velocity, or direction.



    Brian
    Last edited by Brian GC; 03-21-2008 at 12:00 PM. Reason: added info

  8. #112
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,376
    Quote Originally Posted by Brian GC View Post
    Without a doubt. In the same way heat (or smoke) will spread across the entire ceiling, cold air will spread across the entire floor. If a return is down there constantly sucking it out that stratum will eventually be evacuated and replaced by the ever accumulating upper heated strata. This is exactly how a wall furnace, a baseboard heater, a floor mounted heater, and a fireplace works. They produce absolutely no air circulation at all and work just fine. This basic heating principal has not only been abandoned, but it has been reversed with ceiling mounted returns. And, if this principal was used with FAV heaters, you'd have a properly designed system, irrespective of supply throw, velocity, or direction.

    Brian
    Pertinent to the discussion regarding return air placement and influence, allow me to quote from ACCA Manual T, page 7-2, Section 7-3, Guidelines for Locating Returns, addressing combination heating/cooling arrangements:

    In the case of a combination heating and cooling system, the return location depends on when the largest stagnant zone is likely to occur, during heating or during cooling. When perimeter supply outlets are placed low in the room, the largest stagnant zone will occur near the ceiling, during cooling. Therefore when low outlets are used the returns should be placed high in the room. When high supply outlets are used the heating performance is poor and the largest stagnant zone will occur near the floor, during heating. In this case the returns should be placed low in the room.
    So, if I interpret the above quote correctly, return location for heating/cooling combos is dictated by supply outlet location. Hmm...that makes sense.

    What this also tells me is that supply and return location should be a team effort. High supply, low return. Low supply, high return.

    What this does not tell me is where the stagnant zone is during cooling with high supplies and low returns, but that's a given...it's at the ceiling. If a ceiling diffuser is used, or high sidewall outlets actually aimed toward the ceiling, this stagnant zone can be reduced. But...should anyone care about stagnant, warm air against a ceiling where nobody lives? Perhaps not in some of the giraffe barn sized cathedral ceilings in many newer homes...older homes with more modest ceiling heights can use ceiling surfaces to increase throw and reduce drop, increasing total air movement within the room.

    Regarding baseboard heaters, wall heaters, and fireplaces. Those devices heat primarily by radiant heat (granted there is also a convective element involved). If you want to create a comparable forced air situation to these devices, you need low supplies with high returns. Even so, forced air heating and cooling is all about air exchange, not as much regarding radiation for heating.

  9. #113
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    The heaters produce heat,and convection tkes over.

    The return grille doesn't change the temperature,but the supply air does.To me your example supports the reason the supplies are the greater infulence,and return location has little effect on comfort.

    When we built our home,we ducted high and low returns,tried it summer and winter ,couldn't tell the difference.I didn't take any measurements,just home we felt ,so not scientific at all.


    Will you be posting you test/measurement results??

  10. #114
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    Mar 2008
    Location
    Long Beach, CA
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    3,731
    Quote Originally Posted by dash View Post
    The heaters produce heat,and convection tkes over.



    Will you be posting you test/measurement results??
    The most effective test I did was on a 1500 sq. ft. single story house. All dual pane except for one single pane patio slider. 5 year old FAV heater (do not know rating or brand) but did not lack cfm’s, hall mounted ceiling return, registers in every room, and two each in living and family rooms.

    Homeowners were complaining that hallway was always cold and “it seems like the heat that should be collecting in the bedroom is being chilled by the ever cold hallway” that was just outside each bdrm.

    I told them the ceiling return was not allowing the heat to accumulate in the hall and as the bedrooms heated the return was removing all heat below the tops of the doorjambs. So I built a return duct cover out of ¾” Styrofoam that went down the wall and drew off the bottom 5” of floor strata. Unit thermostat was in living room.

    Tested over several days: With original ceiling return, the unit ran 35 minutes to increase room temp from 67 to 72 degrees, and the hallway was always colder than the rest of the house. After the modification it only took 8 minutes to raise the temp from 67 to 72 degrees and the hallway was the same temp as the rest of the house. The thermometer used was away from the hallway and the HO said “it feels like the house is more completed heated”. This is just one example.

    Another was a lower cfm rooftop Rheem heat/AC unit. Well sealed single pane throughout, 1,100 sq ft single story. Also, hall mounted ceiling return. It would not get above 67 degrees in winter regardless of run time. With the same duct device it would reach as much as 75 degrees.

    With results like this I have become pretty stubborn on the subject. I fully understand the circulation effect discussed below and respect it, but ignoring this principal seems, well, just as stubborn.

    Brian

  11. #115
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    Mar 2008
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    Long Beach, CA
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    Quote Originally Posted by jrbenny View Post
    Buy this book. They've done the field testing to show that returns are irrelevant when supplies are correct.
    My test results (below) show the inverse....supplies are irrelevant when a heating return is low. Either one can be considered “correct” if either one can fix the problem.

    Brian

  12. #116
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    Aug 2003
    Location
    Fort Worth, TX
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    Quote Originally Posted by Brian GC View Post
    With results like this I have become pretty stubborn on the subject. I fully understand the circulation effect discussed below and respect it, but ignoring this principal seems, well, just as stubborn.
    Brian
    Please note my quote from ACCA Manual T above, which supports your obstinance.

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