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  1. #300
    Join Date
    Mar 2008
    Location
    Long Beach, CA
    Posts
    3,437
    1) By moving the return upstairs it places the return in the hotter, stagnant zone and continually removes the hottest air as opposed to removing and re-cooling the cooler downstairs air.

    2) In the “before” the cooler upstairs supply air would be “pushed” downstairs by the downstairs return. In the “after” the upstairs return depressurized the upstairs and prevented the cold air from falling downstairs. The upstairs then retained its cold supply air.

    3) With the general air pattern and building pressures forcing an upward draft up the stairwell, this reduces exfiltration type pressures on the downstairs envelope. Reducing upstairs/downstairs temp gradients further reduced infiltration.

    4) Leaks may be present in the extended return ducting. This would pressurized the house and reduce infiltration.

    5) Moving warmer air through the handler is more efficient.

    6) In the ‘after” all structural heat gain that did not get mixed would ascend upstairs and be removed by the return or be mixed with the retained supply air. In the “before” the upstairs supply air was lost to the downstairs and could not offset that amount of heat accumulation.

  2. #301
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,350
    Quote Originally Posted by tipsrfine View Post
    Changing the return location resulted in upstairs t-stat being satisfied by changing the pressure patterns of the home to improve air delivery/mixing & eliminating stratification.
    With the thermostat sensing from the upstairs location, and with the downstairs return grill 90% covered, the upstairs return air grill could actually draw near its nominal inflow, resulting in adequate turnover of air for the upstairs areas. The downstairs still remained cool because that's where the refrigerated air, whether it is introduced upstairs or downstairs, wants to go, since reverse stack effect is still a factor, as you noted above.

    A fundamental component of good air conditioning is successful turnover of air in every room served by the system. You can't get the heat out in sufficient quantities if air in that room never makes it back to the cooling coil. With weak return upstairs and a plume of stratified hot air pooling at the ceiling (aggravated by reverse stack), this was a large contributing factor to Cherokee's discomfort.
    • 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.

  3. #302
    Good summaries guys. My savings is still continuing. I have been on vacation so I have some really low days, but most days in the high
    40kWh to low 50 KWh range.

  4. #303
    Join Date
    Mar 2008
    Location
    Long Beach, CA
    Posts
    3,437
    Quote Originally Posted by cherokee180c View Post
    Good summaries guys. My savings is still continuing. I have been on vacation so I have some really low days, but most days in the high
    40kWh to low 50 KWh range.
    Cherokee,
    You are in the middle of the test area and may be the best person to point out the leading a trailing causing of the increased efficiency of your system.

    Many possibilities have been discussed here. Could you please give us your summary…of course from a theoretical standpoint as we have?

  5. #304

    re

    To be honest with you guys, I think you nailed it. I will review the summaries again when I get a free moment (work has been nuts) and highlight or add to the points. I actually just got on as I got my August bill. It was actually 1 kWh less than my July bill at 1302 kWh and was the lowest on record for August as one of the highest average temperatures (82). I was out on vacation for 4 days, however, that reduced the usage by about 80kWh max. My other August bills have been between 1500 - 1800 kWh and also had full one week vacations in the data.

    Lastly I am having another blower door test done today to re-establish baseline so I can qualify for MD energy improvement credits when they seal my HVAC ductwork using the Aeroseal process this Friday. I will post back with any of the data and my experience using the Aeroseal process. I will also do a video or two. I am hoping my baseline leakage is around 250 - 350 cfm and we can reduce to below 50cfm. This would give me a 20-30% improvement in delivered air into the envelope while also reducing infiltration. I know for a fact that the ductwork leading up to my master bedroom is leaking pretty bad in the walls of my garage, because it showed up as an issue during the IR scan of my garage. You could see the cold temperatures at the top of the garage walls in the bay that has the HVAC ductwork. This may be a contributing factor to our issue in that room. I also ordered 3 more Activents to install upstairs (2) in my Master Bedroom, and (1) in my son's room, to get ready for the winter where they will close if it gets too hot upstairs to again act as a poor man's zoning system. I am really happy with the current units. Stay tuned for additional updates with some pics / vids.

  6. #305
    Blower door test yesterday showed the baseline leakage at 50 kPa is now down slightly to 2078 cfm from 2300cfm a few years ago due to me sealing up a few of the problem areas. I am hoping the Aeroseal process should knock out another few hundred cfm when they test out after the duct sealing process.

  7. #306
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,969
    I think Brian is right about the return placement being able to increase proper air flow to certain areas of the home. I'm picturing what a vacuum cleaner can do by creating a vacuum in an area that allows the presure already present in that area to push dirt up into the vacuum. Why couldn't changing the location of a return positivly affect air flow/cooling to an area? After all, a high pressure needs to be connected to a lower pressure for there to be any air flow at all. We all know what happens to air flow in a room that has a supply vent, no return, and the door is closed---no air flow! The rooms pressure becomes equal to that of the pressure comming out of the vent and air flow stops. Open the door and air flows.
    Brian has already ackowledged this is a remedy that only needs to be used when the supply side delivery/mixing is faulty.
    My biggest problem with Brian is his apparent tendency to have this be his first tool he takes out to fix problems of this nature. The old "If all you have is a hammer, everything looks like a nail" analogy. I think it's a shame his attempt to prove his theory resulted in it being turned into a "I'm right and all the HVAC pro's here are wrong" type situation. No sense in trying to go back and point fingers as to who started that conflict, and I'm sure an arbitrator would find fault on both sides of that coin.
    The good news is that this is probably the end of this age old conflict that keeps appearing in thread after thread, year after year...probably-hopefully.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  8. #307
    Join Date
    Mar 2008
    Location
    Long Beach, CA
    Posts
    3,437
    I realize I have not made many friends here with my often abrasive and persistent approach but my objective was for this to be understood, not to acquire converts. Cherokee has done an incredible job of accumulating data to prove this point, I applaud him.

    Though there are many ways to increase the effectiveness of an HVAC system there is one lesson that should be learned by Cherokee’s test comparison. In the summer the return should be upstairs to cause the naturally ascending heat gain to flow up the stairwell and prevent the cool upstairs air to be lost to the downstairs. When the return is downstairs it will not stop the heat gain from ascending upstairs but will encourage the upstairs cool, supply air to flow down the stairs, only to be sucked up by the return.

    Other factors like infiltration may be at play, but they are minimal in contrast. And for those who doubt this explanation, get your rebuttal ready for when Cherokee comes back in the winter and has to go back to the low return for best system performance.

    Tips, thanks for the acknowledgement. I am thankful that some are coming around to this but I wish more pros would have been involved in this thread, seeing how many have refuted it in the past. These are our natural resources and money that can be saved.

  9. #308
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,350
    Cherokee, forgive me if this has been asked already, but have you had a duct blaster test done? It would give you a baseline for before and after your Aeroseal project.
    • 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.

  10. #309
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Quote Originally Posted by Shophound View Post
    Cherokee, forgive me if this has been asked already, but have you had a duct blaster test done? It would give you a baseline for before and after your Aeroseal project.
    The Aeroseal procedure itself essentially does that with reading airflow rates during the process and recording the starting leakage, the gradual reduction and the final airflow.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  11. #310
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,350
    Quote Originally Posted by lynn comstock View Post
    The Aeroseal procedure itself essentially does that with reading airflow rates during the process and recording the starting leakage, the gradual reduction and the final airflow.
    Good to know. Thanks.
    • 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.

  12. #311
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,736
    Client in Baltimore just had aeroseal done. Because of a disconnected supply they discovered they only got the supply done the first day.

    Immediately noticeable results. Improved humidity and shorter cycles.

    When the returns were done he had whistling. His return ducts now make a lot of noise. (makes you wonder where his return air was coming from before).

    The air sealing crew found attic bypasses and sealed them and a couple dozen can lights. Brought his CFM50 from over 5000 to 1050.

    I guess his ac hardly runs and it feels like Arizona. I want to start selling this aeroseal stuff. For 3x the cost of just diagnostics you can get the work done AND have before and after numbers for plugging into your model.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  13. #312
    I will corroborate the improvements, but my CFM 50 rate was already down to 2078CFM due to other work I had done and then dropped down to 1955 CFM now after the Aeroseal process. Biggest improvement is reduction in basement freezing effect as a lot of leakage was down there, and better airflow in my upper floor. People should read this thread if they are interested in the continuation of this story. http://hvac-talk.com/vbb/showthread.php?t=745181

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