Gas and Oil Home Heating Furnaces - B-vent

I have several questions, I am replacing an existing 100kBTU furnace. Currently, the FLU vents via 26ga pipe throught the roof, with 1" clearance to combustible surfaces. However, I am uncertain if this is acceptable for today's standards. Any thoughts?

Secondly, depending on your answer above, I may consider installing a B-vent. I understand that B-vent is a double walled pipe. Also, I understand the concept of 1" clearance to conbustible materials. However, when installing the B-vent through my roof, does the 1" clearance apply to the outer wall of the pipe, or does this apply to the flu pipe itself? I thought, the outer pipe, provided safe clearance required to the, hotter, inside pipe.

Last, I am not going to terminate the B-vent to the appliance, because two appliances use the same vent. I am going to run the B-vent about 1' below the ceiling and out the roof. I will subsequently, attach a 26ga Y-pipe to the B-vent and run the rest of the 26ga pipe. Therefore, is this acceptable, and do they make couplers to create a "smooth" transition from the 26ga pipe to the B-vent?

Thanx,

Frank

To answer your first question single wall vent pipe used to vent gas appliances requires a minimum of 6" clearance to combustable material. Dry wall is a limited combustble.

Secondly, B-vent as you say is a double wall pipe. The required clearance to combustble material is one inch from the outer jacket.

Finally, there is an adapter from b vent to single wall pipe that is required when you make this transition.

P.S. you should check in the International fuel gas Code for the limitations on length height and sizing of the of the vent that you install.

Good Luck!

This new B vent pipe has to be big enough so it can take two vents in it. You cant put two vents on the same pipe if you dont inlarge it.

Yes the out side of the B vent has to be 1" from all conbustible materials.

Yes they make Increasers and tees for the B vent.

What you have there now, you have get it out of there right now its a NO NO

;) ED

i have always run the singlewall right into the doublewall, i am not familiar with an adapter. how long is the horizontal run, btu's of the appliances, and vertical run, we can give you needed diameter of flue with this.

Thanx for all of the help with my previous B-vent question. The type of furnace I am installing is a Utica MGD-100 Boiler (100kBTU). The vent pipe is 6" 26ga pipe, the total vertical run is ~ 9feet. In addition, a 3" pipe joins near the top of the run for a 35kBTU water heater. I was going to install a 6" B-vent to go through the roof. Is this adequate, if not, what size vent should I use?

Thanx,

Frank

6" will do it