Double Wall vent pipe

[FlameOut]

I installed my 45000 BTU Mr Heater and it works great, but I was a little concerned about the venting.

I bought some 3" double wall vent from HD and installed it with no problems, but I noticed it gets VERY hot. I thought the reason for double wall is the outer pipe will stay cooler??

I'm worried about where it is passing through my wall. It is real close to fiberglass insulation and it's also passing trough the outer OSB and vinyl siding.

Right now I have the hole cut in the drywall and OSB to have a snug fit on the vent. Should I have the openings bigger so the vent doesn't touch? I am also assuming I should be sure no insulation is touching the vent?

Other than that, the heater seems to be working well. Took no time at all to bring over 900 sf up to 60 deg with outside temp at 45

 

[chevelle67]

B vent will still get hot, just not hot enough to ignite surrounding materials. the vent you bought should have a listed minimun clearance to combustables which is 1", so if you have a 3" vent pipe the od is somewhere around 4" that means you need a 6" hole to maintain clearance. There should be a wall thimble where you penetrate the wall to ensure clearance. Did you use a thimble?

 

[FlameOut]

Ok, thanks.

I didn't use a thimble. What is it, like a sleeve? Would that have that at Home Depot or hardware store?

I'll go out now and cut the holes bigger

 

[lametec]

What you need is something like this:

A B-vent wall thimble.

As a side note, I wouldn't be worried about fiberglass insulation touching it.. it's
glass after all, it's not gonna catch on fire.

 

[chevelle67]

thats the piece

 

[FlameOut]

Thanks, going to pick one up today

 

[CraigFL]

I thought that with a lot of these double wall vents, the idea was to bring the fresh, combustion air into the furnace through that outer annulus to cool the inner pipe.

 

[FastEddieG]

I thought that with a lot of these double wall vents, the idea was to bring the fresh, combustion air into the furnace through that outer annulus to cool the inner pipe.

The furnace has to support that, and in my research when purchasing mine, it was ~2x the cost. That's a must have if you have fumes in your area but for my garage, the vented should be fine.
-Ed

 

[pseudorealityx]

The furnace has to support that, and in my research when purchasing mine, it was ~2x the cost. That's a must have if you have fumes in your area but for my garage, the vented should be fine.
-Ed

International Mechanical Code requires 50 cubic feet per 1000 BTU to not require some sort of outside air vented to the space. If you do vent the space, you are supposed to have 2 openings, 1 high and 1 low. (within 12" of ceiling/floor)

 

[Nvr2loud]

I thought that with a lot of these double wall vents, the idea was to bring the fresh, combustion air into the furnace through that outer annulus to cool the inner pipe.

You are thinking of the pipes specifically designed to bring combustion air in along the outer pipe and exhaust out through the inner pipe. B Vent is only double pipe for heat insulation purposes. The outer pipe will not be really hot like the inner pipe. B vent is different from the pipe you are thinking of.