Recently replaced my forced air oil furnace with a 5 ton dual speed WaterFurnace Envision. My HVAC guy told me the not to worry about my ducting as the ECM motor will overcome the lack of duct size. I mainly concerned about my return air vents.
Here are some details;
- 2 story house - 2800 sq/ft
- Near Toronto Ontario
- Two supply ducts 12"x8" and 12"x7"
- Two return duct 14"x6" and 12"x8"
- 18 heat registers feed by 5" dia ducts
- 4 return air vents 15"x7" (2 up stairs, 2 downstairs)
- Design heat loss of 63,312 btu/h
- Heat gain 30,000 btu/h
- Furnace blower settings - 1st stage CFM=1500, 2nd stage CFM=1950
Quite honesty everything seems to be working fine...... slight noise from downstairs return vents, however we're warm. Defiantly much long run times over oil.
I've read many times the CFM should be 400 per ton (cooling?)..... I'm nowhere close. So I having trouble sleeping at night not know if I my ducting is incorrect or I shouldn't worry as the ECM motor overcomes it by pushing more air. Also adding to my confusing is the supply duct on the furnace measures only 14"x14".
I'd very much appreciate your thoughts and advice, Thanks