Air Conditioner on when not home

Reply

  #1  
Old 06-05-06, 03:59 PM
Member
Thread Starter
Join Date: Sep 2005
Location: Where the cows roam, CA
Posts: 2,204
Air Conditioner on when not home

Do you guys leave your air conditioner on when no one is home? If so, at what temp?

Summer is here...or around the corner. This past weekend felt like it was in the 100 degrees mark. It was HOT! I remember last summer I did not leave the air on when I left @ 7am but when I got home about 7pm...it was 80-98 degrees inside (all windows and curtains closed of course). I would get in and run the ceiling fans and the air on and all windows and doors open so it would take a while for the inside to cool off.

This weekend I had the temp set @ 78 degrees and it never got that cold. It ran all day 'til it started cooling off in the evening.
 
Sponsored Links
  #2  
Old 06-05-06, 04:03 PM
lexmarks567's Avatar
Banned. Rule And/Or Policy Violation
Join Date: May 2006
Location: Warren MI
Posts: 610
Do window units count if so I have THREE of them and I leave them running when Im not home.This house faces the sun so it gets very hot in here.I leave them on full cool or 11 on the stat (thats as high as they go.
 
  #3  
Old 06-05-06, 04:09 PM
Member
Thread Starter
Join Date: Sep 2005
Location: Where the cows roam, CA
Posts: 2,204
WOW! Isn't your bill outrageous????!!! It must be nice going home to a "cool" home during the summer time though huh?
 
  #4  
Old 06-05-06, 04:29 PM
lexmarks567's Avatar
Banned. Rule And/Or Policy Violation
Join Date: May 2006
Location: Warren MI
Posts: 610
Don't you know it you have air don't you?
 
  #5  
Old 06-05-06, 06:51 PM
Member
Join Date: Aug 2003
Location: Cape Cod
Posts: 4,320
"It ain't the heat, it's the humidity"

The humidity travels too fast to make it worth it to turn the ACs off when not home
The AC has to work so hard to get the humidity out before you feel a bit cooler
Granted, in a better insulated house it will work better

But as the AC has to work at full capacity just to dry the air before it feels cooler, you are usually better off keeping it on, but set at a higher temp while you are gone

It can actually save you electricity
 
  #6  
Old 06-05-06, 07:04 PM
tae's Avatar
tae
tae is offline
Member
Join Date: Nov 2002
Posts: 2,469
http://michaelbluejay.com/electricity/cooling.html And many other tips...

Q. Which uses less electricity:

1. Keeping the AC on constantly.
2. Having the AC on during the day, then turning it off and opening the windows instead in the evening when it's cool, then turning the AC back on when we go to bed.

The reason I ask is that my roommates think it takes more electricity to turn the AC off and then turn it back on later.-- Julia Van Voorhies, Sept. 2004

A. As I've said many times all over this site, there is no such thing as a household device needing "extra" electricity when it's turned on. So the answer is as simple as you would expect: The less you use the AC, the less electricity you use. When the AC is running you're paying for it. When it's off you're not. So whenever you turn it off, you save money. It's that simple.

Maybe your roommates are thinking that in the evening when you open the windows it's still a little warmer outside than inside, so you're making the inside air warmer, so the AC will have to run longer to remove the extra heat when you do turn it back on. If so, what they're failing to consider is that your house is having heat added to it even if you didn't open the windows. That's because people and light bulbs generate heat, and because the heat from the warm air outside will slowly migrate into your house even with the windows closed. This means that when you leave the AC on it's constantly working to remove that heat. And it definitely takes more energy to remove that heat constantly rather than removing it just once when you turn the AC back on later. See the July 2002 question for more on this.*******

Q. I was reading about turning the air conditioning off during the day to save on costs. I have argued this with my fiancee and others for so long. They believe it should run all day to avoid the cost of trying to get the air back to a 75 degree comfort level. My question is this, you state turning it completely off. Is this efficient to do in the middle of a 95 degree summer, or should I just turn it up to around 85 degrees? -- Kevin Work, Houston TX, Ju/y 2002

A. It doesn't matter what you set your thermostat to (before or after you get home) or how hot it is outside -- you'll always save by keeping the AC off when you're not home. Think about it: Heat constantly penetrates your home, and that's what your AC removes. If you turn on the AC when you get home, then your AC has to remove the accumulated heat only once. If you leave it on during the day, your AC must repeatedly remove heat that enters your home.

You might think that there's no difference, because your house should absorb the same amount of heat either way. Not true. With the AC off, at some point your house will be so hot that it can't absorb any more heat. But with the AC on, your house will always be cool enough to absorb more heat -- and you'll be paying to remove that heat, over and over again.

By the way, if your fiancee isn't comfortable unless the temperature is at a meat-locker-like 75 degrees, then you should probably marry somebody else. Thanks for writing!
 
  #7  
Old 06-06-06, 05:00 AM
Member
Join Date: Aug 2003
Location: Cape Cod
Posts: 4,320
Good article there
Now that I think about it, the way it was explained to me by the HVAC tech, it was in a commercial application with an old and under-powered A/C unit

When the boss turned off the unit at night to save money, in the morning it had to run at full capacity for 4-8 hours to get comfortable

When the HVAC tech explained it like above, the boss decided to keep the A/C on, but higher temp

This absolutely saved on electricity
(I wrote the checks)
But that is a pretty specific example, and not applicable to all situations by any means
 
  #8  
Old 06-06-06, 05:06 AM
lexmarks567's Avatar
Banned. Rule And/Or Policy Violation
Join Date: May 2006
Location: Warren MI
Posts: 610
That is a good link I did not know that but since I home almost all day I just leave the window units running. I gone maby an hour or 3 at the most so I just let them run.
 
  #9  
Old 06-06-06, 07:40 AM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA
Posts: 44,014
I would think that each house could be different. I agree not using electricity is always cheaper I would think a lot would depend on how long it would take to get your home to a comfortable condition. If it only takes a short while to cool your home down it makes sense to turn if off while gone for a while but it doesn't make sense to turn it off and then have to spend a long time cooling it back down.

My house in my location, it is often feasable to turn the air off at bedtime and open windows. With the exception of the hottest nights the house will stay cool and not need air until well into the next day. If the air is left on it will cycle on and off thru the night and run early in the day.
 
  #10  
Old 06-06-06, 08:14 AM
mattison's Avatar
Member
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,549
If a residential system is properly sized it will take several hours sometimes even up to 24 hours to properly remove the humidity in a home. If you were to put an hour meter on a properly sized unit and run it for a week at one temp and then another week shutting it on and off during working hours and also take humidity readings you will find that in most cases the runtime of the unit that is set at one temperature will be less and more comfortable due to lower humidity levels.

Besides the link above is all written by an electrician not an hvac pro. Humidity plays a big part in comfort and a healthy home.
 

Last edited by mattison; 06-06-06 at 08:24 AM.
  #11  
Old 06-06-06, 11:00 AM
Annette's Avatar
Member
Join Date: Aug 2003
Location: Midwest
Posts: 4,158
i keep hearing that, for wood floors & furniture, it's important to keep the temp & humidity fairly constant, or you'll get problems with warping & swelling, etc.

not to mention the dust build-up from having open windows, or the extra bugs, and humidity.....

we run ours all the time. i can't imagine coming home to a hot house. getting into a hot car is bad enough. heck, we even crank it down a little more at night! i loathe humidity!
 
  #12  
Old 06-06-06, 12:06 PM
Member
Thread Starter
Join Date: Sep 2005
Location: Where the cows roam, CA
Posts: 2,204
Great posts guys! Thanks. I think I'll be leaving my air on at a higher degree when I'm out. Does make sense. Not only do we have to worry about our own "comfort level"-I'm perfectly fine at 78 degrees...we have to worry about any plants in the house and like Annette said...flooring and furniture. That's another thing!

In that article Tae posted it mentions about closing isolating unused rooms...calling a pro about which ones to close and how many so no leaks happen...guess I gotta post another thread or search for this answer unless you guys know!!! Tell me tell me! I have 8 vents (I think) and I could go without 4 of 'em b/c the rooms stay pretty cool...
 
  #13  
Old 06-06-06, 05:01 PM
tae's Avatar
tae
tae is offline
Member
Join Date: Nov 2002
Posts: 2,469
Close the doors to the rooms and close the vents. you may find they get hotter than you think, but try it out.
 
  #14  
Old 06-06-06, 05:08 PM
Member
Thread Starter
Join Date: Sep 2005
Location: Where the cows roam, CA
Posts: 2,204
Thanks but I vote to not to try and find out b/c I don't want it to get hot...I'll take your word for it. I take it I should leave the vents open huh?
 
  #15  
Old 06-06-06, 06:15 PM
lexmarks567's Avatar
Banned. Rule And/Or Policy Violation
Join Date: May 2006
Location: Warren MI
Posts: 610
I should leave the vents open huh
I would say so but try closeing them half way or If possible aim them to the hallway and use fans to blow the air around. (I read that in another post.)
 
  #16  
Old 06-07-06, 11:28 AM
mjd2k's Avatar
Member
Join Date: Aug 2005
Location: Canadian Prairies
Posts: 352
When I was working, I set the timer on the thermostat to keep the house cool (about 78 degreess). An hour b4 we came home it kicked down to about 74.

Since no one was home during the day, the house was relatilvly cool so it was perfect by the time we got home.

My suggestion.... buy a programmable thermostat.
 
  #17  
Old 06-07-06, 06:10 PM
nap's Avatar
nap
nap is offline
New Member
Join Date: May 2006
Location: north
Posts: 4,163
My puppy dogs like it cool so the A/C stays on all the time.

On top of that, the last thing I want after a day of dirt dogging in the sun is to come home and wait for the house to start to get cool. The boss won't spring for a new truck with a/c for me so I want it cold when I walk in the door at home.
 
  #18  
Old 06-08-06, 04:35 AM
mattison's Avatar
Member
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,549
Mjd2k makes the best use of a programible t-stat. Taking it up or down 4 - 5 is ok. I would never suggest shutting it down for hours though.
 
  #19  
Old 06-08-06, 02:26 PM
Jay11J's Avatar
Member
Join Date: Sep 2001
Location: Rochester, Minnesota
Posts: 18,433
I totaly agree with Matt.

With heat pump and A/C system, you are almost much better off just set it and forget it!

yes, you can save money when you turn off your system. but man it has to work twice as hard to catch up. My biggest pet peeve is when people shuts off the A/C when they go to bed, open pretty much all the windows. The humdity rushes into dry air. The next afternoon, house warms up, they turn on the A/C and the thing runs and runs trying to cool down the house. All the humidity is sucked into the woodworks/walls.

I only turn up the A/C if we are going to be away from home more than a day. otherwise, it's left alone at 76.

If you want to save money, make sure you do the following things.

-make sure air filters are clean.
-Blower motor/fan is clean and oiled (if has port)
-indoor coils are clean
-outdoor unit coil is clean and clear of grass, leaves, good air flow and NO SHRUBS next to it.
-pull blinds/shades on windows that getting lot of soler gain.
 
  #20  
Old 06-08-06, 02:30 PM
Ed Imeduc's Avatar
Member
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Wink

I think I checked all the post here. And Ill go with MATT. From FL to MO Let the stat alone. Most of the time people like it set at 78o and let it alone.
Over the years have found out that like a cool night or day and you open the home up. Bang it takes over 5 day for the poor AC to try and get the humidity out again to where it should be. So you feel cool at a higher temp.
The main thing with cooling is the humidity. You could like we do in FL run the AC off a humidistat when your not home are going to be gone for a week or so. When you get back you just go back to the stat and set it for 78 and the AC run off it.
This is why the Trane V/S units have a humidistat control you can add to it. With this when the humidity is or gets high it will slow the blower speed down like 80% so the unit can take out more humidity.
On close a room off BAD BAD just think is there any insulation in any of the inside wall?? So any drop in temp in them goes right on through. To close some of them down just a little is good. but you want to let as much air that the blower can blow over the coil there go over it.

Ed my .02 cents
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes