From Heat Pump To Natural Gas

[haydenks]

My wife & I just bought a house in North Carolina that has natural gas heat & central air. Previously, the house I owned had a heat pump located in Central Virginia.
In the past, I pretty-much "set it & forget it" as far as adjusting the thermostat goes, not wanting to engage the aux heat by demand greater than 2degrees at a time. Since I'm no longer faced with aux heat, is it all right to "set-back" the furnace,say at night, by as much as 8 to 10 degrees, and then raise it in the morning, either manually or by a programmable thermostat?

Thanks to all for the benefit of your knowledge/experience!

[coolguysfl]

There's a lot of discussion and little documentation about setting back the T/stat at night.

There are several variables that have to be considered:

1) Fuel Cost
2) The insulation quality of your home
3) The general construction (tightness) of your home to infiltration
4) The efficiency of your furnace
5) Creature comfort - just what feels good
6) Benefit gained / lost with & w/o air moving for IAQ

The utility's claim generically that for every degree you set back your T/stat you can save up to 10% of consumption.. conversely, if you turned your system OFF it would save 100%

The bulk of discussion revolves around the economics of how much fuel is consumed in a steady heat mode (no set back or min. set back) vs. the fuel consumed to recover the home back to the desired set point.

There are different variables that come into play for cooling vs. heating and considerations to relative humidity.

Across the industry, as just an educated experience ratio, 10 degrees is considered acceptable.

The following resource may have some credible data:
http://www.fsec.ucf.edu/en/

[fortressofcomfort]

With gas heat, set back as far as you can stand it for maximum savings.

[docholiday]

Setting back a gas furnace should not be a problem but I wouldnt go bananas with it. If you allow all the "objects" in the house to cool down too far you will end up with a odd feel when it warms back up, the air will be warm but the "objects" like your chairs, floors and other things will be cool. It takes a lot of heat to warm them back up. If you want to go 8 degrees or so, that should be no problem but I wouldnt go much more.

Also if your furnace is sized properly, it may take a while to recover on the coldest of mornings. When you know it's going to be real cold, you might not set it back so far.

[BobbyBJr]

Or purchase a good quality programmable stat with intelligent recovery. It will compensate somewhat for those colder mornings by basing the startup time on how long it took to reach setpoint the day before. I've been setting both my gas furnace and heat pump back 10 degrees for years and rarely notice any discomfort. On a heatpump, you'd want to use a higher end tstat that keeps the strips off during warm-up as long as the heatpump itself is gaining ground.

Bobby