Dumont chimney pipe help

[lotawood]

Hi, I'm new here but looked for years. I am stoked about using a, new to me dumont boiler in the shop. The boiler is piped with 1.5 inch black iron pipe to a 500 gallon propane storage tank. I still need to pipe to existing under floor pipe. The 130 dumont is replacing a memco boiler without storage that was underwhelming. My plan was to run it with 500 gallon storage and add on when I get some experience with the present setup.

What I am having trouble with is chimney pipe. The manual says it is under a slight positive pressure with the dumont's induced fan. So I have checked Security chimney and Metal fab positive pressure chimney pipe. The prices for positive pressure pipe is two to three times the price of normal class A. So I wanted to ask if anyone can suggest a safe chimney pipe that is more wallet friendly than $280 per foot. I just need 10 feet through a simple roof and I thought maybe I am over building it. Thanks.

 

[stee6043]

Does the manual say you need "positive pressure pipe"? Most of our gassers will generate pressure, especially during startup, but I'm not aware of any that require anything other than standard class A pipe.

I personally used a little RTV around the seams in my Selkirk to address the issue of positive pressure when I use my draft inducer during startup. Once you have a good fire going you should no longer have positive pressure.

And last, I wouldn't advise installing your unit without the manufacturer recommended pipe. If they say you need a certain kind - use it. If you choose to deviate you will open yourself up to all kinds of liability should you have a problem with the device at some time in the future, whether or not it was caused by the smoke pipe.

 

[stee6043]

One more thought - typically to meet code you don't techincally need class A pipe until you transition through a wall or ceiling. I'm not sure if this is true in Montana but you may be able to further reduce your cost by using normal smoke pipe inside until you get to your thimble.

 

[lotawood]

The manual does not specify which pipe to use. It says it operated under positive pressure with wood. It specifies 8" round pipe or 8" X 8" tile. For what it is worth, the boiler outlet is 7" and is required to immediately go to 8". It just says of approved construction, free of leaks.

The manual goes on to say all sections of the chimney should be locked together with sheet metal screws and sealed with high temperature sealer or tape. It says to do a smoke test. The place I got it from had single wall stainless steel pipe on it, with adjustable elbows. I saw no sign of sealer or tape. I don't think I could seal an adjustable elbow. I am going straight up anyways.

I looked at Selkirk recently and looked like a good cost effective pipe that could be sealed. I have a Security Chimney on a wood stove that looks similar. But the Selkirk had a sealing band on the outside at the joints. I want to do single wall pipe until just before roof penetration and then insulated chimney pipe from there after, obviously following clearance to combustibles.