Class A Chimney Pipe for NG?

[Crazyjake8493]

I've been using a wood stove in my garage, 6" single wall pipe up to the ceiling, then 6" Class A chimney pipe up to a few feet over the roof peak. I'm looking at taking out the wood stove this summer and installing a hanging natural gas heater that requires a B-vent system.

Is it possible to connect the type B vent (3 or 4" I assume) from the heater to the 6" class A pipe through the roof? I know the Class A pipe is rated for natural gas, but not sure if the increased diameter is an issue. Or could I run the type B vent pipe up inside the chimney pipe and leave it and the existing cap in place? I've installed several HE natural gas furnaces with PVC vents, never with metal B vent.

If these aren't possible, I can always install the heater across the garage against an outside wall and cut a new hole in the wall for the vent system. I don't plan on taking out the wood stove pipe, so I wanted to utilize this existing hole if possible.


Sorry for any stupid questions. Any help is appreciated!

 

[zak77]

I'd say there probably shouldnt be an issue running the b-vent through the class a. You'll need to make a collar of some sorts to take up the space between the exterior of the class b and interior of class a near the cap. That's what i'd do if i were in your shoes.

 

[u3b3rg33k]

Your chimney provides draft - i wouldn't want to increase from 3" to 6" for a small appliance. There shouldn't be an issue capping the 6" on both sides and passing through it with the appropriate venting.

 

[NUTTSGT]

Your chimney provides draft - i wouldn't want to increase from 3" to 6" for a small appliance. There shouldn't be an issue capping the 6" on both sides and passing through it with the appropriate venting.

My thoughts as well.

I think the 6" may be too big for your appliance and may not get a proper draft.

Honestly, I'd send an email to the manufacturer and inquire about the larger pipe before you buy anything.

 

[Showkey]

Honestly, I'd send an email to the manufacturer and inquire about the larger pipe before you buy anything.

Good idea.......qpredict two answers:

We don’t talk to end users on install and troubleshooting questions only certified installers or service techs.

We only recommended venting is clearly printed in the install manual........alternations or combinations of A, B, class III is not approved.

B through the A works........or just take the A down and install a complete B system or classs III and side venting leaving the A inplace for the future.

 

[Crazyjake8493]

Thanks for the input, guys! I think I'll run the B-vent up through the chimney pipe and bend a sheet metal collar for the top and bottom of the Class A pipe to cover the gap.

 

[Jackfre]

I prefer to use either Selkirk or Duravent B-vent. The locking system is better than the competition. They make an assortment of flashings that you could use, at least part of, to flash the Class A pipe. It will take a bit of fabrication and do not screw the flashing to the Class A. I do agree that using the B-vent as a line and the A as a pipe chase is the way to go.

 

[NUTTSGT]

Good idea.......qpredict two answers:

We don’t talk to end users on install and troubleshooting questions only certified installers or service techs.

We only recommended venting is clearly printed in the install manual........alternations or combinations of A, B, class III is not approved.

B through the A works........or just take the A down and install a complete B system or classs III and side venting leaving the A inplace for the future.

Very possible to get that type of response. Although people don't mind spending an hour poking around on the 'net but they don't have time to spend 3 minutes shooting an email out with a few questions.

Not saying the OP wouldn't but just typical behavior of people in general.

 

[Showkey]

True...........I was being a little sarcastic because the garage heater manufacturers seem to be very tight with technical information.........a few have noted here when troubleshooting is requested.