AC Control

Discussion in 'After Hours Lounge (Off Topic)' started by Chris Huber, Jun 7, 2005.

  1. Chris Huber

    Chris Huber Second Unit

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    When you go to work durning the day, do you turn off the AC in your house? Seems like a waste to cool the air 8 hours you are not there...
    Also, to cool the air back down when you get home should not be that big of an energy draw, right?


    How do you guys handle your AC?
     
  2. Dave_Brown

    Dave_Brown Supporting Actor

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    I set mine to be a bit warmer, but to still cool the house when I'm not home. I then turn it down a bit when I do get home.

    I have heard it takes longer and more energy to re-cool the house then to leave it on a higher setting when away at work.
     
  3. Mike Brogan

    Mike Brogan Second Unit

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    I turn it off when I leave and turn it on when I get home, though having a programmable thermostat is the way to go. Either way, turning off saves the most energy. The AC isn't like a gas engine where it burns more fuel to get to a desired speed/temperature so you'll save money by turning off.
    Some helpful tips here
     
  4. Abby_B

    Abby_B Supporting Actor

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    I keep it on but set it so it won't go on as often (then again, I live in an apartment and don't pay a separate electricity bill). I also close the blinds as much as I can so the place doesn't get hotter than necessary.
     
  5. MarkHastings

    MarkHastings Executive Producer

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    My uncle works in the A/C - Heating business and he says not to make drastic changes in the A/C. It's actually cheaper to run the A/C at a constant temp because the unit won't have to work as hard.The fact that the unit will run at full speed until the place is cooled off again (which could take a while), I would think that you'd end up losing all of that $$ that you saved by turning it up during the day (which is how my uncle explained it to me).
     
  6. Micheal

    Micheal Screenwriter

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    I agree Mark.

    Having it set a degree or two warmer while you are out of the house during the day isn't that big of a deal, but shutting it down and having it come back on to cool off the house is expen$ive.
     
  7. Ted Lee

    Ted Lee Lead Actor

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    ditto. i generally keep it a few degrees above/below my target temp.

    so for summer, if i want it to be 77 degrees when i get home, i'll generally keep it about 81 degrees throughout the day. then, when i get home, i kick it down to 77. the house cools down pretty quickly.

    this definitely works better then having the house try to cool down from 95 to 77. [​IMG]
     
  8. RobertR

    RobertR Lead Actor

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    I thought a member posted a DOE link that shot down that idea. It said you should not try to cool the house until just before you get home.

    My heating/AC has 4 independent time/temperature settings for every day of the week.
     
  9. Joe Szott

    Joe Szott Screenwriter

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    Well, I've heard the exact opposite. And based on what I know about thermodynamics, it is no easier keeping a house at a constant cool vs. cooling it down at certain points throughout the day.

    If you think about it for a moment, have you have seen/heard an AC unit or furnace that comes on at half power? Quarter power? No, they come on full blast until the temperature range is reached, then they turn completely off. So how does it work harder to cool it all down once vs. all day long? Sure, it works longer at one clip, but so what? It's designed to do that.

    Or think of it empirically. Let's say we are arguing over an 8 hr period a day (when Chris is at work) where the AC will either be maintaining or off completely.

    Version one: maintain. Regardless of the outdoor temp, let's say the AC must run 7 mins each hour to maintain the temp loss (ummm, 72 deg inside, 92 deg outside). Since it runs full throttle, that means it runs 7 x 8 = 56 mins over the course of the day.

    Version two: off. So no maintenance running, but let's say it takes 30 mins to bring the temperature from 92 to 72 in one shot one hour before Chris gets home. Then it maintains the temp for 3 mins in the next 30 mins, rounding up is 34 mins.

    Again, since the AC is either 100% on or 100% off at any given time, it would seem that version two offers significant advantages. Not only is the AC unit not sucking as much electricity, but the filter also isn't getting as dirty. One more point to make is that the hottest hours of sun in the day are 12-4 pm. If he isn't trying to cool his house during those peak times, there is a good arguement for even more savings by not combating the worst of the heat.

    I think you should get a programmable thermostat Chris and do some experimenting day to day. You know, let it cool all day one day and take meter reading before/after, then turn it off the next day and take some readings (and note the outside temps of course as well.)

    Let us know what you discover...


    PS - I don't even have AC, so this is pedantic ramblings. I use an Evap. Cooler, came with our house and does the job 90% of the time. But regardless, a programmable thermostat is the way to go whatever you decide.
     
  10. Philip_G

    Philip_G Producer

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    The only thing joe leaves out is the heat absorbed by your walls, furniture etc. You've got to pull that out. You also hit a brick wall at the dewpoint and have to dehumidify to get below that, taking more energy.

    so which is better? fucked if I know.
     
  11. Ted Lee

    Ted Lee Lead Actor

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    [​IMG]
     
  12. Micheal

    Micheal Screenwriter

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  13. Micheal

    Micheal Screenwriter

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  14. Todd Hochard

    Todd Hochard Cinematographer

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    Having experimented with this at length when I lived in FL, I found that kicking the system up 5* while we were gone was optimum.
    You have to consider humidity infiltration and heat soak of your walls and "stuff" in the home, too.

    Any PROPERLY sized AC unit is going to take WAY WAY longer than 30 minutes to drag the indoor temp down 20*. On a hot summer afternoon, my unit could take 2+ hours to pull down from 92 to 79.

    You only save energy, if the house reaches equilibrium. That may or may not happen, even over an 8 hour period.

    If your going to get a setback thermostat, get one with a run time meter. Then, you can try it all ways, and see which works for your home.

    Todd
     
  15. MarkHastings

    MarkHastings Executive Producer

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    Yes, the key (as I said in my first post) is to not make 'drastic' changes.I'm not exactly sure, but I can't imagine it's good to have the unit working constantly for many many hours each day. I would think the larger units can handle this (like in office buildings), but the smaller "home-sized" versions may not be up to such tasks on a daily basis.

    I kind of compare it to exercising. Working out 30 minutes each day is a lot better for your body than working out for 4 and a half hours straight, only one day a week.

    Again, I'm not sure if this is a fair comparison, but it seems like it would be.
     
  16. Joe Szott

    Joe Szott Screenwriter

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    I don't see how comparing a mechanical device to a biological system is a straight comparison, but ok. Do you pull your car over to 'rest' a couple of times each hour so it doens't get 'tired' and give it something to eat, or do you drive straight to where you need to be because it is a machine and not an animal? And if you wanted to make the comparison, isn't closer to saying working out 1 hour a day vs. 5 mins each hour you are awake?

    Anyway, that's just being argumenative [​IMG] Seems like folks in the know have the answer here, a 5* shift while you are out is optimal in your area (the South).
     
  17. Holadem

    Holadem Lead Actor

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    That is one bizarre comparison Mark. Literally apples and oranges. One's got nothing at all to do with the other.

    --
    H
     
  18. Philip_G

    Philip_G Producer

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    air conditioners are opposite, if the compressor could run 24/7 it would run for YEARS. Trane has/had an old compressor that has been running for 20 or so years straight, but if you shut it down it would probably not start back up again. You might find a story on it by searching "old frosty" on google.
     
  19. MarkHastings

    MarkHastings Executive Producer

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    Source - They recommended a 5 degree difference between the time you're away and the time you return.

    So this definitely seems to be the most energy efficient difference.
     
  20. Rob Willey

    Rob Willey Screenwriter

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    Another factor here is that your electricity provider doesn't charge a fixed price for juice all day long. When demand goes up, such as when everybody returns home from work, $/kwh goes up too.

    That said, I've heard it is best to cool the house throughout the day rather than all at once when you get home, but I've always found that counter-intuitive.

    Rob
     

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