Have been reading threads here for some time, and everyone has been most helpful in many projects. Currently insulating my attic and was getting ready to insulate around my b-vent when I noticed it seemed larger than need be. Went down in the basement and looked and here is my setup:
80% 66,000 btu fan assisted Bryant furnace, 3' single wall connector, 2 elbows, no horizontal runs
40 gallon, 40,000 btu with draft hood, 2' single wall connector, 2 elbows, no horizontal runs
Both the furnace and water heater vent through 4" single wall pipe to a 6x5x4 sheet metal wye. The 5" outlet has a 4" reducer that connects to the furnace. The 6" end of the wye then connects to a 6" b vent that travels straight up, no offsets, through a wall chase and through the roof where it terminates, approximately 16'-17'.
From all the sizing guidelines I have read, it looks like I should be running a 4" b-vent connector from the furnace and can use a 4" double wall for the common vent up through the roof. I currently have 6" b-vent for my common vent. Will this cause problems with condensation and furnace efficiency? If I'm going to fix it I want to do it right!
Any help is much appreciated!
Thank you to all in advance.