Need to run 5" B vent through 8" chimney pipe

rubantin

I am replacing a woodstove with a 65,000 BTU/Hr Enclosed Front Console Propane Gas Room Heater (Williams model 6501521A). I need to run a 5" double wall B vent through the 8" chimney pipe that has 2 45s and 15' of straight pipe through the roof of a 2 story house.

1) Do I need to seal the space around the 5" vent at the bottom and top mof the 8" flue?

2) Can I take remove the 8" pipe up to the 1st floor ceiling and then run the 5" through the 8" to the roof? That would eliminate the 2 45s

3) What do I do at the chimney cap? Do I remove the 8" top and do the same same thing I did at the bottom, extend out the 5" vent and put on a 5" cap? Or can I run the 5" vent up to the 8" cap and just leave it open inside?

Any advice would be appreciated

ChrisJ

I'm not a pro, but wouldn't a flexible liner be a whole lot easier and probably cheaper?

How are you going to lock the connectors together inside the chimney?