This unit is a 100,000 Btu upflow gas furnace with a power vent, and on the vent instruction's that vent pipe may be B-1 pipe to vent outside. I'm wondering it's it alright to vent directly into the chimney with 5" smoke pipe, the furnace is 20" away from the chimney. It notes that Common venting is allowed. Follow the National Fuel Gas Code. ANSI Z223.1 and/or the Natural Gas Installation Code, CSA-B1149.1