Newbie here (please be as patient with me as you can and let me know if I am breaking any rules).
I am remodeling my new house. I am replacing the furnace and am moving it from the closet in the foyer to under the house. I live in Salinas, California, where freezing nights are extremely rare.
My contractor has suggested a New American Standard, Under-Floor Furnace with a new Return Air Duct with Filter Grill and a Digital Setback Thermostat.
He also suggested that I go for 2-speeds and 2-stages.
As I understand it, once the house has reached the desired temperature, the other stage would reduce the number of heating elements that came on once the temperature dropped, thus saving propane, and that the fan would come on at a slower speed, thus saving electricity.
But I don’t understand. Doesn’t the thermostat continue to ask for more heat until the house again reaches the desired temperature? If fewer heating elements are on, then, instead of propane being used quickly for a short time, aren’t I just using half as much propane but for twice as long?
Then, as for the variable speed fan, if the air is being pulled/pushed through the ducts at a slower speed, spending more time under the house, won’t there be more time for some heat loss than when the fan is at full speed? Wouldn’t the rooms at the farther ends of the house tend to be cooler then than those in the middle? And wouldn’t this effect be compounded if the air isn’t as warm to begin with because only half of the heating elements are in use? And again, wouldn’t I be trading the speed of the fan for the amount of time the fan had to be on?
I’ve been told that the 2-stage, 2-speed thing will keep the temperature more even, without large drops or over-heating the room before turning off, but the furnace in my current house (which is the same size as my new one) seems to do a perfectly good job without any of the foretold temperature extremes. Have furnaces just been changed to the point that single-stage/speed furnaces now run hotter and faster than they used to?
The cost for the 2-stage/speed is $1000 more than the 1-stage/speed version, which is a 15% increase. There are other things I can spend that on if the variable stage/speed is not necessary.
So, if my logic is all messed up, remember, I have already admitted I don’t understand this at all. Please explain it to me. I don’t like being in the dark.
Thank you for taking the time to answer.