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  1. #66
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    Mar 2008
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    Quote Originally Posted by beenthere View Post
    You say you tested this.

    But, you haven't. Since you never tried using the right supplies.
    …and you are quick to discredit my theory while never testing it either. I could walk you into several homes where only my approach would work over yours. They have very open floor plans with high ceiling. These poor people have heaters in their attics with ceiling returns and they shiver all winter long. They have resorted to using space heaters downstairs while not even bothering to use their heaters anymore. But no worry, the GC, HVAC contractor, and architect got their pay for another job poorly done.

    I feel for these people as the HVAC industry should. If the HVAC industry was more sensitive to these people and they know the answer is these “magical” registers, why don’t they abolish old registers and highly criticize these inept systems as I do?

    Brian

  2. #67
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    Mar 2008
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    Quote Originally Posted by kamikaze126 View Post
    so if your job is sealing house envelopes (im guessing that means saving people money on thier energy bills) and your saving people 50% on thier heating bill by showing them your invention. Why are you not charging them for this? surely anyone would be glad to pay for an idea that would save 50% on thier heating bill.
    I’m a GC who routinely insulates exterior walls, attics, and install a lot of energy efficient windows and doors. I’m not in the ducting business.

    Brian

  3. #68
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    Mar 2008
    Location
    Long Beach, CA
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    Quote Originally Posted by beenthere View Post

    So his house sealing is worthless.

    Incomprehension, frustration, and criticism are sometimes a simultaneous occurrence.

  4. #69
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,754
    I'm in ana area, where we commonly use high and low returns.
    So your wrong on that.

    You haven't tried changing the supplies, so you don't know if your covering up a problem, by curing the symptom, or fixing it.

    Since you don't see how much your sealing saves them first. You have no idea if the lower return is doing anything to save them money.

    A real test would have a control, and only change one thing at a time.

    So, your just spectulating.

    You have posted most of this in other threads already.

    You saying the same thing over and over, hoping it becomes true.
    But you don't really test it.
    You just claim to.
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  5. #70
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,292
    Quote Originally Posted by Brian GC View Post
    I realize these manuals are Bibles to the industry but I have performed field tests too. The results are amazing. If the HVAC experts can’t recognize this or if they are simply disregarded, their credibility in my opinion is diminished.



    They do not grasp it because they have never seen what is accomplished with such a simple change like this does. Also, the HVAC manuals obviously won’t lead a person to it either. So where are they to gather this knowledge? BTW I have heard of HVAC contractors who follow this rule, but they are few.
    Although Manual T explains that the "sphere of influence" around a return air intake is small, regardless of location, I've been thinking about that aspect more globally, in that while I agree with Manual T's thought in principle, I also trend toward the understanding that a return air grill drawing air from a room affects the air pressure surrounding the intake.

    The thrust of this discussion is that if supply registers are high, low returns are best for heating. The thought that a low return draws cold air off the floor, heats it, and reintroduces it back into the room through the high supplies is not in dispute. The focus is one of total air movement in a room with supply and return air provision, and whether location of either affects air distribution and comfort performance. We already know that improper supply air distribution can lead to discomfort, especially if a blast of supply air enters the "occupied zone" of the room, which is measured from near the floor to just over six feet above it. This blast of air can feel drafty to most people. So the HVAC designer is then charged with not creating such a condition. He does so by careful supply register selection, one that will allow maximum throw and spread, which in effect entrains air that surrounds the supply jet. Air from the occupied zone will actually be drawn up toward the supply jet as the entrained air needs make-up air to continue the entrainment process. If the air near the floor is cold, it will be drawn up, causing the occupants to feel discomfort. Why is the air near the floor cold? Insufficient thermal boundaries, ranging from infiltration to inadequate glazing that allows cooling of air adjacent to the glass to sink to the floor, adding to a pool of cold air in that region, are among many contributors to a cold floor condition.

    The low return with high supplies creates a low pressure region at the floor. The supplies above introducing heated air do so at a higher pressure. The entrainment of air occurs at higher levels in and/or above the occupied zone, with lower regions showing influence toward a low return. Manual T supports this, in that if the system's primary task is for heating, and supply air introduction must be high, low returns are best.

    Equipment in the attic has its own set of flaws. Putting it in the attic is what brought about ceiling returns because it simplified the install. It aids in the performance of the AC and weakens the performance of the heater.
    That was precisely the point behind my tirade against attic installs. It was a builder decision, most likely, over any other trade associated with HVAC installation. Ask any tech or installer; he/she would LOVE to stay out of a superheated attic during a summer heat wave and service equipment on the ground. Ask any builder why the equipment goes into the attic, the near unanimous reply will be regarding maximizing the square footage of the floor area for living space and/or storage.

    Attic installs hinder a/c performance just as it does heating performance, because the ducts are not in the conditioned space, nor the equipment. In my area, many homes were built with the equipment in a hall closet and the ducting in the attic. This is an improvement, but not ideal. Yet it does yield the benefit of low returns. Few homebuilders are willing to build a soffit and drop ducts into them, although one did, Fox & Jacobs, and did it on a massive scale, finding economy as well as making it a marketing point for their homes.


    A flawed or inadequate ducting system (and attic ductwork) can easily diminish the system efficiency by 50%. Unit specs of efficiency are too easily quoted by HVAC contractors as what a HO has in his house. Other factors (ducting and attic installs) are glossed over when quoting the real efficiency of the system.
    Let's take an 80% furnace rated at 80,000 input btuh. Output around 64,000 +/-. To see a total loss of 50%, as you suggest is possible, would mean the sum total of all supplies into the home, only 32,000 btuh is reaching the interior of the structure. You would be saying, in effect, that 32,000 btuh is being lost to the attic. Meaning, if the furnace is moving 1,200 cfm of air, raising the return temperature from 70 degrees F to 119 degrees, it is then emerging from the supply registers at ~94 degrees, due to losing ~ 32,000 btuh to the attic (1.08 x CFM x delta T).

    So there you have it...if you ever wish to determine if your 50% loss is anywhere near actual in the field, that's how you could determine it. I grant some installs might be that bad...even then it would depend on the outdoor ambient temperature, and that of the attic air and structural members.

    I don’t build new homes but I did recently lay out the ducting-runs on a job and forced the HVAC contractor to install a low return. He didn’t agree with my theory, but most HVAC contractors don’t.
    He might have "disagreed" because his equipment was up in the attic, and adding the low return ate into his job cost if you didn't compensate for his time and material.


    Saving on heating bills involves many aspects of a house. I agree, floor returns are only one of many.
    We're on the same page, there. There will inevitably be a house that cannot practically accomodate a low return mod for an existing high return placement. A house such as this will require other remedies to yield greater comfort to the occupants. Return relocation is not a cure-all for the wounds.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  6. #71
    Join Date
    Mar 2008
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    Quote Originally Posted by shophound View Post
    The thrust of this discussion is that if supply registers are high, low returns are best for heating. The thought that a low return draws cold air off the floor, heats it, and reintroduces it back into the room through the high supplies is not in dispute. The focus is one of total air movement in a room with supply and return air provision, and whether location of either affects air distribution and comfort performance. We already know that improper supply air distribution can lead to discomfort, especially if a blast of supply air enters the "occupied zone" of the room, which is measured from near the floor to just over six feet above it. This blast of air can feel drafty to most people. So the HVAC designer is then charged with not creating such a condition. He does so by careful supply register selection, one that will allow maximum throw and spread, which in effect entrains air that surrounds the supply jet. Air from the occupied zone will actually be drawn up toward the supply jet as the entrained air needs make-up air to continue the entrainment process. If the air near the floor is cold, it will be drawn up, causing the occupants to feel discomfort. Why is the air near the floor cold? Insufficient thermal boundaries, ranging from infiltration to inadequate glazing that allows cooling of air adjacent to the glass to sink to the floor, adding to a pool of cold air in that region, are among many contributors to a cold floor condition.
    The accumulation of cold air on the floor is constantly being replenished by the typical R-2.5 dual pane window. That is why I feel it so important to just remove this cold air with the proper ducting layout rather than trying to stir it up.

    Quote Originally Posted by shophound View Post
    The low return with high supplies creates a low pressure region at the floor. The supplies above introducing heated air do so at a higher pressure. The entrainment of air occurs at higher levels in and/or above the occupied zone, with lower regions showing influence toward a low return. Manual T supports this, in that if the system's primary task is for heating, and supply air introduction must be high, low returns are best.
    I often use my fireplace to heat my downstairs. It does the job very well without moving any air at all. I believe it employs the theory of low returns to do so by: constantly radiating heat while constantly removing the low strata of cold air off the floor. And by allowing the heat to collect on the ceiling and work its way down. I doubt a radiant floor heater that produced the same heat would work as well if the exhausting/removal process did not take place.


    Quote Originally Posted by shophound View Post
    Let's take an 80% furnace rated at 80,000 input btuh. Output around 64,000 +/-. To see a total loss of 50%, as you suggest is possible, would mean the sum total of all supplies into the home, only 32,000 btuh is reaching the interior of the structure. You would be saying, in effect, that 32,000 btuh is being lost to the attic. Meaning, if the furnace is moving 1,200 cfm of air, raising the return temperature from 70 degrees F to 119 degrees, it is then emerging from the supply registers at ~94 degrees, due to losing ~ 32,000 btuh to the attic (1.08 x CFM x delta T).
    I’m not saying the furnace output or the heat at the supply registers are decreased by 50%, I'm saying the arrangement and type of ducting can affect the overall performance by 50%. A hypothetical example: If a supply register was blowing directly into a return grill and the house temp was unaffected, the system efficiency would be 0%. As you pulled the two apart from one another the house temperature would rise and the overall efficiency of the system would increase dramatically. My 50% estimate is when an improved ducting layout can raise the room temp in half the time, thus equating to a 50% more efficient system from what it was originally.


    Quote Originally Posted by shophound View Post
    He might have "disagreed" because his equipment was up in the attic, and adding the low return ate into his job cost if you didn't compensate for his time and material.
    In that case the unit was in a laundry room and the old system return was ceiling mounted. It could have gone either way and at no additional work either way. But if it was an added expense to HO, I agree it would be a hard sell opposing both the HO and the HVAC contractor.

    Quote Originally Posted by shophound View Post
    We're on the same page, there. There will inevitably be a house that cannot practically accomodate a low return mod for an existing high return placement. A house such as this will require other remedies to yield greater comfort to the occupants. Return relocation is not a cure-all for the wounds.
    I agree, most two story homes would be next to impossible to mod.



    Brian

  7. #72
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    Feb 2007
    Location
    Great Lakes Region
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    A hypothetical example: If a supply register was blowing directly into a return grill and the house temp was unaffected, the system efficiency would be 0%.



    This is why the thread should be closed

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