Page 2 of 24 FirstFirst 12345678912 ... LastLast
Results 14 to 26 of 312
  1. #14
    Quote Originally Posted by skippedover View Post
    Brian GC, what you're simply running against is those who are uneducated. As you've stated, you STUMBLED across a solution that worked for you. Well, a true pro can't afford to just stumble across a solution. He needs a scientific solution that works every time. That begins with a blower door test to establish the air infiltration/exfiltration rate. That rate is then used for a Manual 'J' calculation, that takes all the physics of the structure into consideration. Then a Manual 'D' design is made for low static and adequate air supply to each room in the home, again, based on the shapes within the structure. Manual 'T' is used to determine exactly which register/diffuser should be used on each outlet, as the actual CFM delivered from each supply can vary with the design of the register/diffuser.

    If all of that work is done (rarely and it yes, it costs) then the system should be properly sized and will work properly. Issues that can be more readily solved with zone controls would also be revealed in the design process. When the supply side of the system is properly designed and installed, the actual location of returns is far less critical. However, return location should not be ignored. It does have an effect on the airflow through the occupied space and therefore deserves as much attention as the supply side. But all-in-all, the location, sizing and airflow characteristics of the supply outlets trumps the location of the returns, as long as the returns are adequately sized for the system.

    So once again, this isn't a carp shot nor is it a guessing game. When a company takes the time to actually design and install properly, using the established science available, the results are stellar. When the science is ignored, well, garbage in, garbage out, right?
    Very well written and I fully agree.

    The problem is most of us are dealing with a house where the HVAC system was an afterthought in the house design process that was awarded to the lowest bidder in a high volume development scenario, with very little actual engineering employeed. At least that is very common on the East coast. I have used all the tools you suggested including a full energy audit, blower test etc to start to attack my issues.

  2. #15
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    Brian, cherokee180c

    Brian, as the HO said
    .
    Funny thing is my system as designed works great in the winter without doing anything,
    You do seem to find it convenient to not hear/ read what you find inconvenient to your point of view!

    cherokee180c, the statement:
    Did you not advocate for high-low, the" you can never have too many returns" approach?
    was directed to Brian I wrote:
    I (genduct) happen to agree with a single, high, ducted (no building cavities) return with "jump" or transfer ducts that may be ONE stud space so that the air has a path back to the unit and the difference in zone pressures is less than 2 pascals.
    This is what I have said on several occasions and have found the best approach with the lowest amount of static pressure used (wasted) on the intake or return side of the unit.

    My original statement still stands:
    What many of "us" have been trying to share with you (brian) is:
    a brilliant return duct location will NOT make up for a lack of supply air.
    Since the remark was meant for Brian and you weren't aware of the "history" I can see how you were confused by the remarks. Hope that clears up my opinion about your situation
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  3. #16
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    PS cherokee180c, you wrote:

    I want most of the return air pulled from the first floor, there is no need to cover up anything, since the original design already provides the airflow pattern highly biased to the first floor return.
    which seems to contradict somewhat your earlier statement.

    For the record, if you did in fact leave your obstructed 1st floor return grills alone, and did pull most of the air from the high area My opinion is it would be just as effective
    No need for high/low or adjusting etc. Most of the air problems posted here are supply problems and are not solved with only, additional brilliant return locations.

    Man, this subject does get beat to death. It is clearly like a strongly held religious view and the passion runs deep!
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  4. #17
    Join Date
    Mar 2008
    Location
    Long Beach, CA
    Posts
    3,323
    Genduct,
    Cherokee, correct me if I’m wrong. The reason your system “works great in the winter without doing anything” is because it draws the majority of the return from the downstairs. If you left the supplies alone and drew most of the return from upstairs, it wouldn’t warm the house as effectively, true?

    A “single, high, ducted return” would not be as effective in the OP’s house in the winter. It might decrease static pressure but it is not best for heating. His current low return priority is best for heating, just listen to what he (we) are saying. We are following simple physics.

    The reason I jumped in here is to emphasize the fact that the OP has found exactly what I have found to be true. Locating or balancing the returns so they remove the stagnant, unwanted air first will greatly improve the performance of a system. Of course if the system was designed correctly from the start, as Skippedover outlined, it wouldn’t be so effective. But as we all know most homes/systems are not designed with that amount of care.

    You can continue to disagree with this or not grasp it but the OP’s very impressive data speaks for itself. Or maybe you can explain away his data?

  5. #18
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    Brian, do you not agree with the Man T?

    Locating or balancing the returns so they remove the stagnant, unwanted air first will greatly improve the performance of a system.
    As has been pointed out to you, the effect of the return grill on that terrible, stagnate air is really low. This is where we part company, like Al Gore, you avoid any science that doesn't suit your needs.

    I do see some movement in your position though. In a short time you, like Gore will have invented the internet and will come to embrace the simple fact that you can't suck comfort into a space.

    Keep evolving, you're getting closer to "us" guys
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  6. #19
    Join Date
    Mar 2008
    Location
    Long Beach, CA
    Posts
    3,323
    Quote Originally Posted by genduct View Post
    As has been pointed out to you, the effect of the return grill on that terrible, stagnate air is really low.
    Tell that to the OP. He has data that contradicts your claim.

    …and will come to embrace the simple fact that you can't suck comfort into a space.
    I’ve done it, and the OP has done it.

    Keep evolving, you’re getting closer to "us" guys
    I have no interest in thinking like “us guys”. I get my evidence from actual results like what the OP did, not from a bunch of nay-sayers who lack experience.


    I'll ask you one more time. Show you know what you are talking about by commenting on the data the OP got [post #1].

  7. #20
    Join Date
    Dec 2004
    Location
    Chicago area
    Posts
    1,439
    genduct,

    I am not understanding your argument here.

    Design your next system without high returns, and ballane the supplies precisely to the load, and see how effective that is.

    A single story application may work due to the air rotation effect from the supply velocity, but try it on the second floor, or in a tri-level house, when all the returns are pulling from the floor on the 1st floor.

    A/C 101 remove the heat from the space, if your returns don't pull the hottest air, you will not cool the space.

    I see this scenario all the time in malls in the winter. The engineers never thought to add an exhaust fan for when the cooling is coming from outside.

    Blast all the cool air you want at the problem, but it can't cool if the heat has nowhere to go.

  8. #21
    I have a two story house where the upstairs is much hotter than the downstairs when I am using the central air system. The system was originally designed for heating and I have a main 24x24 return located in the downstairs living room and I also have 12x12 return located in the upstairs hallway. All the supplies and returns are located near the floor.

    I recently had a new 95% efficiency Rheem system installed. At my request, the contractor installed a second return in the upstairs hallway about 5 feet above the original return. When I switched from heating to air conditioning, I closed the lower upstairs return with plastic and left the downstairs return unobstructed. I also changed the dampers in the basement to force more cold air upstairs (opened 100%) and less downstairs (closed 50%). The suction of the downstairs return is much stronger and the upstairs return will barely hold a tissue.

    These changes have made a difference, but I am wondering if the system efficiency could be further improved. I have the following questions:

    - Would closing off the downstairs return by 50% help pull more from the upstairs return?
    - Will the system always be limited since the original supply ducts are undersized (I believe they are 6" ducts)
    - Can changing the blower speed help with providing more cold air upstairs?

    My primary concern is heating, so I would not want to make any changes that would impact heating since this is my primary need and this works fine.

    Thanks

  9. #22
    Join Date
    Dec 2004
    Location
    Chicago area
    Posts
    1,439
    Closing vents will do little if anything. And as far as the returns go, it depends how the returns were ducted. I would try blocking off the 1st floor return 50 percent or so to see what happens with the 2nd floor return.

  10. #23
    Join Date
    Mar 2008
    Location
    Long Beach, CA
    Posts
    3,323
    Heatingman,
    I agree with your post 100%, it’s nice to see pros here get it. Too many do not.

    I’d like to expand on a few of your comments as I see it.

    Quote Originally Posted by heatingman View Post
    genduct,

    I am not understanding your argument here.

    Design your next system without high returns, and balance the supplies precisely to the load, and see how effective that is.
    In the summer, heat loads that penetrate the thermal boundary do not remain where they come through the walls. They naturally rise upwards. Conversely, A/C supply air does not stay at one level, it sinks to the floor.

    Heat load is bad air, A/C air is good air – why position a return low in the summer to remove the good air? Why postion it high in the winter to remove the good air? It's mind boggling that this is not understood.

    A single story application may work due to the air rotation effect from the supply velocity, but try it on the second floor, or in a tri-level house, when all the returns are pulling from the floor on the 1st floor.

    A/C 101 remove the heat from the space, if your returns don't pull the hottest air, you will not cool the space.
    You might be able to cool an area by pumping tons of cool air at it, but it is a wasteful approach. Let air density do what it does and position the returns accordingly.

  11. #24
    Join Date
    Jun 2011
    Location
    Southern, Ohio
    Posts
    4
    What about installing a "Zoned System"?

  12. #25
    Thanks for your response Heatingman. The upstairs return is right above the downstairs return, so I know the ducts ae directly connected to each other. I did quickly try to partially block the downstairs return and the upstairs return was definitely pulling more air. I assume this is what I want to happen.

    Is their any negative consequences to doing this on permanent basis when using the air conditioning. Any other considerations? Is this common for individuals to do with my type of setup?

    Thanks

  13. #26
    Join Date
    Jul 2009
    Location
    Northeast, Md.
    Posts
    126
    I have not had time to read every page so i don't know everything suggested. My opinion is that closing off downstairs returns, and pulling your return from upstairs will help remove the stagnant air from up stairs. The supply air may not drop sensible heat upstairs, but removing the latent heat from upstairs will help make it feel cooler to you. That's how Psychrometrics work on the skin.

    This does have a effect on the refrigeration cycle though. Since Hot air rises you have a higher heat load on the evaporator. Your system is going to work harder then it normally would, and your temp splits will be off that higher temp because you have a constant supply of warm air across the coil. Even though the downstairs is cooling off your only pulling the warmer air from upstairs which makes it harder for the T-stat to satisfy.

    I recommend closing no supplies off until you have a tech out to see your pressures. Let them tell you whats acceptable. Airflow is detrimental to a AC system and there is some shabby ductwork here on the east coast. Closing off too many supplies could get you a block of ice!
    Last edited by budman21901; 06-25-2011 at 10:49 PM.

Page 2 of 24 FirstFirst 12345678912 ... LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event