Hi Everyone, I am getting ready to replace my furnace and had a few questions about what I would like. I have 3 contractors comming over but wanted to get the pro's opinion. Did a manual J and have a total heat loss of 70KBTUH and a heat gain of 40KBTUH. It appears that based on manual J 75KBTUH at 95% AFU would be great at a 3.5 ton coil. On the heating size the first floor is 68% of the total load and the second floor is 32%. This seems to line up perfectly with a 2 stage furnace output setting.
This is what I am thinking, not sure if it is possible. All main trunk lines are in basement and easily accessible. Is it possible to zone a 2 stage furnace for the above loads? If the furnace kicks on low, 52KBTU for the second floor, and it only needs 22KBTUH, will I be overfiring the furnace? Also, how are the ducts sized for the varios CFM outputs of the furnace? If they are sized for the max, and it is on low, static will be very low?
Sorry the question, just want to get my head around how a 2 stage multi speed operates and if you can zone them and if a static pressure bypass damper is needed in the setup.
Any recomendations on brand would be welcome and appreciated.
Thanks for your help.