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Optimal programmable thermostat settings for mid-atlantic?

post #1 of 7
Thread Starter 

I have a programmable thermostat (2 actually, greenhome.huddler.com/products/honeywell-rth7500d1007-thermostat) and I'm trying to figure out the sweet spot for setting the "sleep" settings for heat).

 

A quick overview on the settings:

Wake

Leave

Return

Sleep

 

I can set a temp setting and time for each.

 

So, my question is, how "low" can I set the temp and still have the unit be efficient when it needs to heat the space back up (they call it "recovery"). I have a feeling if i set it too low (say 50 degrees) and then it has to heat the space back up to 72 degrees that the additional gas used to heat up the space might be more than it would to maintain that space at 72.

 

I know there are tons of variables like sq footage, tonnage of furnace, insulation, windows etc, etc.. but I was hoping for some generic rule of thumb or basic equation. I'd like to get the setting as low as possible on this thermostat since this zone is on the first floor and we sleep on the second (a different zone/thermostat).

 

The home is only 3 years old, so I'd give good marks on insulation and windows and we live in the mid-atlantic, so night time temps can drop into the 30's/20's on average. This zone is gas if that makes a difference (i think it does).

 

Any ideas thoughts or opinions would be appreciated.

 

Thanks


Edited by pgallett - Mon, 23 Feb 2009 15:32:46 GMT
post #2 of 7
Quote:
Originally Posted by pgallett:

 

So, my question is, how "low" can I set the temp and still have the unit be efficient when it needs to heat the space back up (they call it "recovery"). I have a feeling if i set it too low (say 50 degrees) and then it has to heat the space back up to 72 degrees that the additional gas used to heat up the space might be more than it would to maintain that space at 72.


 

This is a case where the lower you set it (in the colder months), the better.

 

Here's the way I think about it.  Your heating system heats up your house to a temperature higher than the outside air.  Because your insulation isn't perfect, you're always losing heat to the outside until the temperatures are in equilibrium - when your home is the same temperature as the outside air.

 

So, anytime you've got your thermostat set above the outside temperature, you're going to have to use some energy to keep it there.  The bigger the temperature difference (the higher your inside temperature), the more energy you need to use, because the more heat is seeping out of your house.

 

If you suddenly heat your house from say 50 degrees to 70 degrees, it does take a lot of energy, but you're using that energy over a short period of time, and you're not losing much heat to the outside in the meantime.  Where you lose the most energy is if you're keeping your home temperature much higher than the outside temperature over a long period of time, because you constantly have to replace the heat you're losing outside.

 

It's a difficult thing to explain, but hopefully that made some sense.  Basically you're better off raising your home temperature a lot over a short period of time than keeping it at a higher temperature over a long period of time.

post #3 of 7
Thread Starter 

Sounds good, 50 degrees it is :).

 

Unfortunately, we are getting towards the end of the season and uber cold nights, so I may have to put this experiment off till next winter.

 

I was leaning towards the lower setting, but have heard conflicitng info in the past. I just didn't want to shoot myself in the foot with a crazy gas bill.

 

I have the opposite issue in the summer, but that's another discussion.

post #4 of 7

The principle is the same in the summer.  Keep the temperature high when you're not home and you'll use less energy cooling your house.  I set it to turn on a half hour before I get home so that it has time to cool the house down a bit.  Also since we have dogs who spend time inside while we're gone, I don't keep the temperature too uncomfortable when we're gone.

post #5 of 7
Thread Starter 

Yeah, summers a different beast for me since I work at home and have cooling issues in my office (it's on the 3rd floor and I get simmered by the heat from floor 1 and 2). I personally begin to melt when the air temp gets over 65, so it's an ongoing battle.

 

I need to figure out some math and find out how long it will take to recover the cost of adding a 3rd zone for my office (right now the 2nd and 3rd floor share the same zone) that I can keep frigide (without cooling the 2nd floor).

post #6 of 7

Well, does anyone know where i might be able to find a proper Programmable Thermostat, as mine had some wiring problems and had to have it repaired. The cost of having it repaired is twice of what it is actually worth. So where can i get one, best buy, malls? anyone?

post #7 of 7

If you can wait a few days (which is a big IF), I'd shop on Amazon. If you need it locally, Home Depot, Lowe's, or the like are probably your best bet. Hope this helps!

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