Was at a call today noisy furnace upon taking a quick look around started to notice multiple code infractions anyways long story short gas is off to both a cv water heater and fan assisted mid furnace .
Question I have is bvent is inside of the home ect is there a max allowed length to be outside above the roof or no ?
Also no way to drop a liner to both appliances so pitched him on hi eff firm and new pv tank
Anyone else ever run into this sad thing is the furnace is only 5 yrs old but major venting issues have caused damage inside unit another fly by night guy burned a customer again
Are you asking how long in total the B-vent can be or how high above the roof it must extend?
QuoteClause 8.14.4 - A chimney shall extend not less than 3 ft (900 mm) above the highest point where it passes through the roof of a building and not less than 2 ft (600 mm) higher than any portion of a building within a horizontal distance of 10 ft (3 m).
You would use Table C.3 or Table C.4 to size the venting. You would need to know the diameter of the existing B-vent and the chimney height, as well the BTU's of each appliance vented up the chimney.
The topic says B-vent outside, but you mentioned the B-vent being inside of the home.
Download Director's Order FS-051-04 - Here (http://www.hvactechgroup.com/article.php/20070429202902486?query=b-vent)
Keep in mind Director's Order FS-051-04 was revoked and replaced by Annex N in both the B149.1-10 (FS-212-14) and B149.1-15 (FS-225-17) Code books.
Download Director's Advisory FS-052-04 - Here (http://www.hvactechgroup.com/article.php/20090407213614589)
Don Park B-vent is max 6' above roof line if that is your question.