This is my first time posting to this forum, which I found while googling for information on furnaces. I have found some valuable information on these sites, but I still have some questions.
I moved into my house last February, so only used the original furnace 2 months or so. It was an 82,000 BTU Lennox furnace which was about 25 years old. When I went to start it this fall, it needed a new blower, and the electronic ignition was obsolete, so I needed to purchase a new furnace.
I chose the Bryant 95I Preferred variable speed 2 stage furnace, and had a Lux TX9000TS single stage thermostat installed with it.
In reading about multi stage vs single stage thermostats, I still am not sure which would be the best set-up. It seems people differ on which is best. Right now with the single stage thermostat I have, it appears the furnace is doing most of the decision making on when the furnace runs. I notice that the high speed runs more than the low speed (which I understood would only happen in the coldest of weather, which I took to mean in the low teens and below). I also notice the high speed sometimes runs well past the set point on the thermostat, sometimes to the point where it almost gets to hot in the house. The other thing I notice is that sometimes the furnace won't come on right away when the temperature shows 2 to 3 degrees below the set point, and thus it gets a little cold. Is there some kind of timing interval on the furnace to keep it from running again to soon, so it doesn't overheat (I think I read this somewhere)?
My understanding of a 2 stage furnace was that having 2 speeds allows the furnace to run longer at a lower speed, thus giving a house more even and constant heat. I thought the high speed would only be needed occasionally. But it seems to run more than the lower speed. Wouldn't a 2 stage thermostat help cut down on these variations of temperature? Having a timer determine when the furnace runs, doesn't seem to be the most efiicient way to use this furnace.
One last concern: There is a loud gurgling sound on the vent pipe on the outside of the house. It doesn't do this all the time, but I do notice it mostly when I come home from work in the evening. Could this be due to the furnace being set at a lower temperature (62) during the day, and then going back up to a higher temp(68) in the evening? Is this normal, as I don't hear it on my neighbors vent pipe (she doesn't have a two stage furnace, so maybe that's the difference)? Seems this could be a concern with the condensation backing up and causing rust/mold issues.
By the way, last week I had foam insulation sprayed in the side walls. I have not noticed any change in the furnace running. I thought by putting insulation in the walls, the heat loss would take longer, and thus the furnace would run less. Is there some adjustment I should have the furnace installer make to the furnace default settings due to the insulation in the walls?
Thanks for any insight you can give. I appreciate it.