Air Conditioning - Whats the best way to set the Thermostat during the day while your gone?

I've heard both arguments. Mostly by your typical "experts".


Leave it set at one constant temperature throughout the day.
Increase the temperature several degrees while your gone.


Well, I'm currently utilizing option #2 with questionable results. My electric bill this month is the highest its been in the last two years. I know electricity costs have increased this year due to higher fuel costs, but we definetly used more kilowatt hours this past month then the same month last year.

Currently, I set the thermostat at 83 during the day when we're gone, and I have it automatically jump down to 78 in the afternoon and remain that way until we leave the following morning and its back up to 83. Keep in mind we're down here in Phoenix and the daily temps are anywhere from 110-120. I remember living in Chicago when the temps were in the 90's, we would have the A/C set to between 68-72. If we did that down here, we would free our arses off. Anything below 76 and its time for long sleeves...lol.

So, whats the best method for Temperature Manipulation throughout the day when the house is empty?

id go with one if its as hot as you say other wise you would be trying to fight to get it back the way you want when you get home and it will take a long time to get there thats why the bill goes up

Ill go with #2 also. Have you checked the inside coil is it clean? Blower wheel clean?New filter over 30 days. When running is small copper line warm to hot and big copper line cold and wet at the outdoor unit. That should tell you the freon is ok.

ED;)

When it got to 114 two days ago in california, my house would only get to 80 degrees...

Just keep the AC to a high temp and you will save money, no need to keep it very cool when it's that hot out anyway.

The gain in monetary savings is when the temp is at the away setting. The savings letting it warm up is canceled by the cost of cooling it back down. If it's high for a while, you save. During the day like this, you might not see much savings.

You know, I might have knocked out two birds with one stone. My wife closed off two unused bedrooms and their associated A/C vents. Leaving only the Master Bedroom, Master Bath, and Laundry Room A/C vents opened on that side of the house. In turn causing an imbalance in the system.

I started another thread trying to find out why my A/C vent in the Master BDRM was rattling. It also sounded as if the airflow was real erratic. After opening up both vents in the other two bedrooms, the airflow seems much smoother and the rattle is gone. Hopefully this will help out with my inefficient solution as well...

On SRP's (My energy provider) website, they recommend the following: http://www.srpnet.com/energy/ess/cooling.aspx


Leave at least 90% of the air vents open in your home. Closing air vents in more than 10% of your total conditioned space creates a pressure imbalance. This reduces the effectiveness of your cooling system.
During the summer, set your thermostat between 78-80 degrees when you are home, and 85 degrees or higher when you are away. For every degree you set your thermostat above 80 degrees, you can save approximately 2-3% on cooling costs.


Thanks for your help all!

It will likely take some experimentation but I suggest setting the thermostat as high as you can while you are away & still getting the place comfortable by the time you return.
In my house, the thermostat stays at 75º 24/7 simply because my A/C won't "catch up".

Grady,

Since you are in the business, why won't your particular unti catch up?

Sized to the bare minimum?

Super hot where you live?

Poor insulation in house? (I'm not a big fan of that real white fluffy fiberglass insulation that don't itch. I have seen the stuff 2feet deep in attics and I can feel moist air escaping in the winter and see rafters blanketed in ice crystals. I think that insualtion is TOOO loose. If you step on it walking in the attic, it disappears like cotton candy or Wonderbread. JMO.

Too many windows?

House painted black? :)

What kind of temp blows out your registers?

The equipment was oversized per Manual J when I put it in but there have been some significant changes since then. I've added a room (aprox. 250 sq. ft.) with a lot of glass (low E but still glass) & I leave the door to the basement open to the living area. In the basement there are two freezers & a boiler. None of this was taken into consideration on the original sizing. My equipment will maintain temp on a design day but if the temp gets up to or near 100º & the humidity goes sky high, the best it will do is 76º. Still not bad for a 15 year old 12 SEER Janitrol to which I have done NOTHING other than change filters & wash down the outdoor unit a couple of times a summer. Duct insulation is only R-4 & the ducts are in the attic. When it craps out I'll re-do the whole system.

Grady,

Since you are in the business, why won't your particular unti catch up?

HVAC guys always have poor running and poorly maintained equipment. We work on it all day so the last thing we want to do at home is work on our own. One of these days I'll change that pesky filter.

How much you can turn it up when you're not home also depends on the humidity in your area. If you live in a dry climate then go ahead and crank it up a little extra. If you live where it's humid like I do just set it and forget it.

Just like me. I need a new tub surround...badly! I've needed to replace that rotten Marlite sucker for years. :)

The roofer's place needs a new roof, the mason's chimney needs re-pointing, etc., etc.
Mattison is right on the humidity thing too. It's a lot tougher getting the moisture out than dropping the temperature alone.