mgbinspect 2 Report post Posted March 9, 2011 Here' one for the brain trust: A 44,000 btu furnace with a draft inducing blower (right flue) A 88,000 btu furnace with a draft inducing blower (center flue) And a 75,000 btu gas water heater - gravity (left flue) ALL share this flue. It seems to me that it should have stepped up another size after the third flue joined in. Undersized? Any thought? Click to Enlarge 69.73 KB And, all three units are crammed into a 6 x 9 unvented room in the finished basement ... hmm.... Quote Share this post Link to post Share on other sites
hausdok 19 Report post Posted March 9, 2011 OK, You know that with my second grade math skills I can't do the math for you but the flue must equal the largest connector plus 50% of all others. Get out a pencil. ONE TEAM - ONE FIGHT!!! Mike Quote Share this post Link to post Share on other sites
mgbinspect 2 Report post Posted March 9, 2011 OK, You know that with my second grade math skills I can't do the math for you but the flue must equal the largest connector plus 50% of all others. Get out a pencil. ONE TEAM - ONE FIGHT!!! Mike That'll work. Thanks. Quote Share this post Link to post Share on other sites
Marc 75 Report post Posted March 9, 2011 OK, You know that with my second grade math skills I can't do the math for you but the flue must equal the largest connector plus 50% of all others. Get out a pencil. ONE TEAM - ONE FIGHT!!! Mike Do you mean that the cross sectional area of the main flue must equal the area of the largest flue plus 50% of the combined areas of the remaining flues? Where does this rule come from? Marc Quote Share this post Link to post Share on other sites
mgbinspect 2 Report post Posted March 9, 2011 I believe we're talking volume - a little geometry ala pi. Richtig? If memory serves, it's V = 2 pi R Nah. That can't be right. That's got to be circumfrence. V = piR squared. I think that's it, but I'll look it up. Yes pi R squared is correct. Quote Share this post Link to post Share on other sites
Marc 75 Report post Posted March 9, 2011 Area of a circle = (Pi) times (Radius squared). Pi = approximately 3.14 Sorry Mike O. I couldn't help it. [] Marc Quote Share this post Link to post Share on other sites
mgbinspect 2 Report post Posted March 9, 2011 No prob. I haven't used any of those formulas since I left the drawing board. Many moons ago. I was reaching. Quote Share this post Link to post Share on other sites
David Meiland 1 Report post Posted March 9, 2011 It would be worth finding out if there's spillage at the water heater draft diverter when the furnaces fire up. Quote Share this post Link to post Share on other sites
