Hardly Working

I'm a carpenter asking the Pro's this one. What is the best tempatures to set a programable T-stat at with a 7 day program. I know what I like and feel comfortable (warm) at, but what is going to save me money and keep me warm. Right now it set like this.
Wake 69
Leave 56
Arrive 69
Sleep 60
So what's your house set at? Oh as a side note I'm located in the Seattle area in Washington state so no extreme temp swings except for this week. Lovely 25-33 degrees with snow.

mdshunk

Mine's on about 75 all day, and I crack a window when I sleep. That's no joke.

SLSTech

Hmmm, question looks familiar
http://www.contractortalk.com/f22/wh...r-house-48415/

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Hardly Working

Damn that Search box . Thanks. Between the jokes and BS I think I'm in the ball park.

Dr Heat

Set the temp were you are comfortable. Then remember the set back should be less than 5% of the set point, anything more will not be cost efective.

Even electronic stats are not accurate so there is no benefit to talk numbers. We are told 72 with 45% RH. Summer 40% and 78 seems good.

That being said I set mine at 58 and have no humidifier.

If you heat with wood you will need to add humidity at higher levels. still the same 45% rh though as temps drop outside lower rh so you do not get moister then mold on windows.

Incidentally if you have a tight house and a 90%+ efficient furnace you will not save much if any (certainly not the cost of the stat)

90% of my customers set the stat to 72 then press the hold button.

ATH

Can you please provide data to back up this claim?

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mdshunk

I remember reading that on a Department of Energy pamphlet. Anything more than 5 (degree) setback for 8 hours or less gets used up again when you reheat the place when you get home. More dramatic setbacks will yield net savings if the away time is very long or for a period of days.

I do agree that a programmable thermostat on a plus-90 furnace is silly. The upcharge for that stat makes the payback close to 10 years.

ATH

Thanks, I'll have to look for that pamphlet. If you can provide a pointer it would be appreciated.

I do like that your answer has time associated with it. It appears to me that a simple answer of % or degrees is a bit too simplistic.

I would really like to see experimental results that show a point at which it is no longer a savings.

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duckdown

My thermostats are programmable and allow temperature to vary M-F vs the weekends. M-F from 6pm to 6am, the temp is set at 68. Outside of these times, I set it to 65. During the weekends, I have it set at 69.

ATH

I've searched through the Dept of Energy WWW site without finding the reference cited here. I did, however find a couple of other statements that do not support the 5% (or 5 degree) statements:

from http://apps1.eere.energy.gov/consume.../mytopic=12720

"You can save around 10% a year on your heating and cooling bills by simply turning your thermostat back 10°–15° for eight hours."

and

"The fuel required to reheat a building to a comfortable temperature is roughly equal to the fuel saved as the building drops to the lower temperature."

This statement seems to imply that one would not save any energy (nor expend extra energy) until the setback temperature is reached and that you get the savings for each minute the temperature is maintained at the lower level. I'll have to ponder that one for a while.

A similar statement to the first was in a number of places, including:
http://www1.eere.energy.gov/consumer...rgy_savers.pdf

"You can save as much as 10% a year on your heating and cooling bills by simply turning your thermostat back 10% to 15% for 8 hours."

These documents did, of course, exclude systems like heat pumps that have a hard time altering the temperature quickly without resorting to expensive electric resistance heat, etc.

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Dr Heat

The old Honeywell install guide recommended the 5% setback. I've been doing this for 28 years and have grown extremely weary of all the money saving gimmicks and how much they will save in energy and cash. Some examples

Vent dampers (you will save 15 to 20% on fuel bill)
Chronotherm stats
70 80 90 90+

Some actually save money some do not but none of these work when used improperly.

My point based on the things I have been taught in years of listening to sales pitches dressed up as tech classes, nothing works like the salesmen say.

Use sense, insulate and heat your home leave the stat alone.

flashheatingand

I agree that usually, nothing works like the salesmen say.There are a lot of examples. But...

In my opinion, a programable t-stat will save a lot of money if used in a home that uses a gas furnace or electrical furnace as heat. Here is my reasoning.

Imagine riding your brand new ten speed bike from Christmas. There are the gears that have no resistance, and your legs are pumping hard and not getting you far. Then there are the gears that seem to give a little resistance and you get good distance. Finally there are the gears in which you need to get some momentum and then you get good distance with a few pumps. Well, convection heating systems are a lot like the low resistance gears and radiant heat is a lot like the high resistance gears.

Remember, you are only heating the air in the building with gas furnaces. It doesn't take too long to heat that air, and the air will cool down quickly as well. So, use it while you are home and lose it while away. Also, it is better that the furnace run steadily as opposed to cycling on & off.

I can't say that I have any data or lab experience to back this up. It's just my reasoning. With radiant heating systems, and heat pumps, I would say leave the t-stat alone. But, otherwise I believe they will pay for themselves within two years. And feel free to have 10 degree temp swings.

Having said that, it is important that the end user know how to use the programable t-stat. Otherwise potential for head aches are "a-plenty"

oldguy2

hello to everyone. yes i am new here and have been surfing the hvac site.been installing hvac for 24 yrs now and really never got into the service side of it b/c most companies ive worked for always had a seperate service side. so basically i installed the product if she dont work id call the office and they would send in a service guy to fix it.but anyways being on a resi job site new home construction. i had a customer ask me why his furnace runs more if he sets it at a lower temp at nite then if he sets it a few degrees higher. i find their house cooled ive never kown anyone that set the temp this low.during the day he sets the stat at 17c = 62.6f and at nite it is set at 14c =57f he says the furnace comes on more often at this setting.if he sets it at 16c = 60f its not on as much.he thinks at 14c the furnace should be off longer i said no cuz theres no heat in the housethe furnace comes on more i'm just at a lose trying to explain why the furnace runs more.details furnace90plus hieff house is 2400sq two story t-stat pro 3000 honeywell. new home constuction so standard insulation no upgrades home faces west in ontario canada near ottawa.and yes it had heatloss heatgain and duct design

Dr Heat

Just because I am a know it all on the web (I am more humble in person)
A few thoughts:

1 Stat's are less accurate (as any meter would be ) the further you get from the mid setting.

2 at cooler temps the heat anticipater may operate differently

3 gremlins

4 I think it may just be because he is fixated on the furnace at night

Or I could be just guessing

sorry

HVAC

This is similar to how I have mine set as well. I don't agree with the 5% rule although I may be wrong. As long as the system is fairly new, the lower and longer the stat is set at a lower temp, the more you save, even if it is over 5%

Dr Heat

I went back to some old tech papers from the late 70's its a carrier guide. This is old so disregard if you want, but the detail said 5% for an 8 hour set back on heat nothing said for ac, further in the text it said two percent per 8 hours additional set back.