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  1. #14
    Join Date
    Sep 2005
    Location
    Bay Area, CA
    Posts
    843
    THe most efficent air conditioners are ones that dont turn off and match btu gain in the summer. Long run times are better for the system, short cycling or excessive cycling will cause strain on the system and can reduce system life.

    As far as what temp at night it should be, depends on your climate and house, I just leave mine at 72 heat load on the house is reduced at night so it rarely cycles anyway and I cant sleep at 80 degrees.

  2. #15
    Join Date
    Jul 2003
    Location
    Philadelphia Pa.
    Posts
    461
    In past years I would keep the stat set to 76 during the days, and then 73 for a return and night time temperature. 73 all weekends.

    Last summer I started working at home and kept the temp set to 73 all the time. I am on a billing budget and two months ago I got my new monthly billing amount which increased from $173 to $210 per month I guess as a result of running it 73 all the time, but not sure.

    Now I am thinking about running it 76 during the day starting at 7:30am, 75 for a return temp at 5:30pm and 74 during the night starting at 11:30pm. 74 during the weekends. I am just going to sit at home during the day with little to no clothes on. Do you think I will realize any savings from these temps or would some other pattern be better?

  3. #16
    Join Date
    Sep 2005
    Location
    Bay Area, CA
    Posts
    843
    I also let my customers predict the tempature, when they get a new system or a new customer, I tell them set there tstat at 80 degrees, and leave a notepad by the thermostat. If during the next two weeks you have to lower the temp more then you dont have to then program the occupied time two degrees lower and repeat.

    I've found more customers doing this will actually end up keeping there thermostat set higher. I of course tell them to repeat the procedure when they upgrade the insulation or windows as well.

    You have to get through to some customers that yoru comfort is not a # on a thermostat, 72 at your office does not feel like 72 at your house.

  4. #17
    Join Date
    Jul 2003
    Location
    Philadelphia Pa.
    Posts
    461
    I can say right now that I can not stand 80F

  5. #18
    Join Date
    Apr 2008
    Location
    MO. USA
    Posts
    46
    Quote Originally Posted by jerrod6 View Post
    I can say right now that I can not stand 80F
    76F to 78F yea, but 80F? No way.

  6. #19
    Join Date
    Apr 2008
    Location
    Beaufort,SC
    Posts
    16
    I personally have found that a setback greater than 4-5 degrees during the day cost you more money. The residual heat load you have from 80*F down to 72*F at night costs you a lot more money than keeping a tighter temp range. The guy is thinking backwards though, like everybody else has said longer runs are better than short cycling but it also costs a lot of money if it has to run for hours to bring the house down to temp. Much cheaper to run it for 30-45 mins to bring the house down a few degrees rather than a couple of hours from 80*F. MY .02s.....

  7. #20
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,452
    I think we covered all the possibilities with the previous answers. For the future, we should have systems that can be off when the home is unoccupied during normal wealther conditions for several hours/days/weeks. The system should have enough capacity to reach comfortable temperatures in about a hour or two. This will save a tremendous amount of energy. Eight -10 hours of "off" during the heat of the day would reduce cooling energy by +50%. The system that can cool down in a couple hours will also handle extra occupants during hot weather. A slightly over-sized simple a/c is capable of providing these temperatures. Yes, ideal humidity control is impossible during wet cool weather. Let us get another issue on the table.
    The other issue is fresh air ventilation. Homes that have the correct amount of fresh air to purge indoor pollutants and renew oxygen providing a healthy inviornment for the occupants are now required by more and more codes. The ASHRAE minimal recommendations are 7 cfm per person plus .1 cfm per 100 sqft of home. The recommendation assumes additional fresh air will infiltrate from various sources. Overall, an air change every 3-4 hours is ideal. When oudoor dew points are low (<50^F), moisture generated inside the structure (1 lb. per hour per person) is controlled by fresh air change. As the outdoor dew point excedes 50^F, the indoor %RH increases. The level of relative humidity for health and comfort for most is <50%RH. Exceding 65%RH, supports dust mites, mold, and is uncomfortable. Many require lower indoor temperatures to be comfortable at higher %RHs.
    Using the above post, proper fresh air ventilation while maintaining 80^F would result in a wet home after several air changes. You solve the problem however you want. Healthy, comfortable, and economy are a must in a well designed system. I feel most of you know my solution. Be back later. Regards TB
    Last edited by teddy bear; 05-07-2008 at 10:28 PM. Reason: correct gramar
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  8. #21
    Join Date
    Apr 2008
    Location
    MO. USA
    Posts
    46
    teddy bear: Excellent points!

  9. #22
    Join Date
    Jul 2003
    Location
    Philadelphia Pa.
    Posts
    461
    Quote Originally Posted by jerrod6 View Post
    In past years I would keep the stat set to 76 during the days, and then 73 for a return and night time temperature. 73 all weekends.

    Last summer I started working at home and kept the temp set to 73 all the time. I am on a billing budget and two months ago I got my new monthly billing amount which increased from $173 to $210 per month I guess as a result of running it 73 all the time, but not sure.

    Now I am thinking about running it 76 during the day starting at 7:30am, 75 for a return temp at 5:30pm and 74 during the night starting at 11:30pm. 74 during the weekends. I am just going to sit at home during the day with little to no clothes on. Do you think I will realize any savings from these temps or would some other pattern be better?
    Do you all think I am going to save any money with these proposed set backs or should I try something else?

  10. #23
    Join Date
    Apr 2008
    Location
    Beaufort,SC
    Posts
    16
    Valid points indeed T.Bear but down here in the south where we have RH of 70-85&#37; most of the time that theory doesn't work so good. Most of the time down here we need to get the humidity out, not in. Didn't work when I lived in Western N.C. either where it rained all the time. All depends on your climate.

  11. #24
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,123
    You'll save some. How much, only time will tell.
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    How many times must one fix something before it is fixed?

  12. #25
    Join Date
    Apr 2008
    Location
    Beaufort,SC
    Posts
    16
    Quote Originally Posted by jerrod6 View Post
    Do you all think I am going to save any money with these proposed set backs or should I try something else?
    Sounds to me like you would be better off investing in some insulation first. I added 18-20" of blown insulation in my attic and my light bill fell from $250 in the 95*F summer down to a nice consistent $108. My a/c kicks on about every once in awhile. Oh yeah and I put in an attic power vent fan. By the way I have a 20*F delta too.

  13. #26
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,123
    Insulation effects the light bill?

    Oh, you meant your electric bill for cooling.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

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