Oil Boiler Flue Vent Option

ken22079

Hello, in need of some advice for an oil boiler flue vent. Currently, the flue is connected in the chimney. We will be doing major renovation and the chimney will be demolished.

A new flue vent will need to be put in. Do I need a class A 6” insulated double wall or a 6” B vent sufficient? Both will need a 2 inch offeset.

Thank you.

Intplm.

A good way to start is to find out what your boilers manufacturer suggests. From there you can build an exposed piped chimney, a new conventional chimney, a chimney liner or a type of power venter that vents through an outside wall.

ken22079

Thanks, I’m trying to avoid the exposed chimney (not a fan of the look) and power venter (extra component to maintain or breakdown). I can easily run a new chimney pipe and enclose in wall. I know Class A is completely fine but B vent is a concern bc it’s not for boilers but 2 contractors suggested this.

Class A option was to Duravent DuraPlus triple wall chimney pipe. Metalbestos was way too expensive.

Steamhead

B-vent is for gas only. L-vent can be used with oil.

EBEBRATT-Ed

What @steamhead said . No B vent use Type L

Bob Harper

B-vent is aluminum inner liner with an outer galvy casing rated at 1" clearance to combustibles with a maximum operating temperature of 550F. It cools the stack temps by conduction. It can offset to 90 degrees from vertical with long horizontal offsets. It is air cooled.

L vent is similar to B-vent with these exceptions: The inner liner is stainless steel. It is rated for a 3-clearance to combustibles. It is rated for 570F max continuous but also a 1,400F flash fire. It runs with hotter stack temps because the ss liner does not conduct away as much heat as aluminum. It carries a lifetime warranty. It is air cooled.

Class A factory chimney is also called "All-fuel" chimney because it is rated for CAT I gas, oil, and wood under natural draft. It requires a 2" clearance to combustibles. The "HT variant is rated for 1,000F continuous, 1,400F for one hour and 2,100F for 10 minutes run x3. It can offset a maximum of 30 degrees from vertical. It is heavy because it is insulated with solid packed insulation. That means it keeps the stack gases warm, even when exposed to direct exposure. Because it is so heavy, it requires substantial support. It carries a lifetime warranty.
HTH,

EdTheHeaterMan

@Bob Harper is correct on all the different vent specifications however this does not say whether B-Vent can be used on a fuel oil boiler. I am here to say that you can not use B-Vent on an oil fired boiler because most if not all oil fired boilers may exceed the maximum 550°F temperature on a regular basis. Even if you can get the boiler to operate with a 350°F temperature regularly, there is always the availability for a professional technician or DIY repairman to install the next size larger nozzle and leave it in there.  In a week or 2 you will read about how the fire department showed up after that wrong nozzle event only to find a damaged vent that almost brought the house up in flames..   Or did burn the place down.   

The bottom line is the boiler manufacturer’s venting instructions.  That will tell you if you can use L-Vent or not. And if not, then you need to go with the Class “A” manufactured chimney, or “All Fuel” manufactured vent system.  

Here is some information from the International Association of Certified Home inspectors (whoever they are) https://www.nachi.org/type-b-l-vent-inspection.htm

ken22079

Thank you all for the comments. I will proceed with the class A triple wall for a piece of mind. It’ll be enclosed and frame with metal as well. May be overboard but it’ll make us feel safer.

Last obstacle is the flue going straight up from the boiler and will need to have 3-4 pieces 45 degree turns so that it will come out the back side of the roof. Kind of like a Z shape. I see they sell the fittings and assume this is ok.