My friend just got a variable speed furnace installed and he was very happy that it eliminate some cold spots in his house.
I have a two-speed furnace. With fan always on it seems not eliminating the cold spot (two room addition on the 2nd floor, always cold w/o inline booster fan ON). It actually gets less comfortable in warm rooms, since the fan circulate cold air when the furnace is not on. I can feel cold air out of the floor vent.
What is the advantage of variable speed furnace? If the furnace is not always ON, what is the difference? Thanks in advance.