gasifier class A chimneys rated for draft induced appliances

[loggie]

I have got my switzer 1250 in my basement and will be running a class A chimney up thru my attached garage from my basement and after looking at the simpson and selkirk brands they both say they are not rated for positive draft appliances only natural draft only,simpson makes one rated PT for this purpose which I cannot find out any more about. I will have a 3/4 hp inducer on my system (part of the switzer)Anyone else run into this?

 

[TCaldwell]

Loggie, Have you asked what the reason for this is, the pipe is stronger than the single wall pipe gary normally use and it could be sealed with high temp silicone. the garn is induced through most of system and pressureized or positive flow to discharge flue gas,it reccomends a simpson type class a , for it's discharge. Many boilers with higher flue temps do not mandate a class of flue only the size and let local codes dictate safe install. How long will the flue be, my garn has 18 ft of class a that has a 2hp or about 450cfm of volume and no ill effects.

 

[webbie]

It would seem as if oil boilers were forced draft......I guess they cannot have a blanket testing cert. because they would have no particular situation to test to.

 

[loggie]

I will have about 16' class a from the inducer in the garage up thru the garage attic and thru the roof.I will have about another 20' from the inducer to the boiler most of this will be single wall pipe.I know gary says this is ok,it raises a red flag with me if this one thousand dollar chimney is not rated for this installation,I can use hi temp rvt on the seams and or foil tape but wonder why it is not rated for this.The only thing I can think of is if the chimney were to become blocked the joints could not contain the flue gases under the pressure of the inducer.with my boiler inside my house I am trying to keep everything proper.

 

[BrownianHeatingTech]

Is the Switzer positive-pressure, or just induced-draft? They are two different things.

The presence of a draft inducer does not mean that the gasses will be pressurized relative to the ambient air. The size of the inducer, and the level or restriction in the pipe after it are the determining factors in that. If the chimney and connector are large enough relative to the size of the inducer, there will still be negative draft - the inducer will simply reduce the degree of negative draft, but not actually create positive pressure.

Joe

 

[loggie]

Joe, you pose an excellent question,but reading the simpson manual it says not for anything other than natural draft.My inducer will be mid stream in the chimney with strait pipe out 8" dia probably not much pressure there and three 90 degree turns on the suction side of the inducer.I guess I am wondering If everyone uses this pipe on there gasifiers

 

[BrownianHeatingTech]

Joe, you pose an excellent question,but reading the simpson manual it says not for anything other than natural draft.My inducer will be mid stream in the chimney with strait pipe out 8" dia probably not much pressure there and three 90 degree turns on the suction side of the inducer.I guess I am wondering If everyone uses this pipe on there gasifiers

Having an inducer is still natural draft, as far as the chimney is concerned. Natural draft, in terms of a chimney, means that there is negative pressure at the point where the flue pipe connects to the chimney. As long as that pressure is negative, you still have a natural draft chimney.

Joe