TEMPORARY galvanized stove pipe

[Maple River Sugar]

I am asking about the feasibility of using galvanized stove pipe in my temporary set up for boiling sap.

I will be boiling under a lean to which has a 24" over hang. If I place the evaporator out enough to allow proper clearance from the soffit I will be exposing the evaporator more than I want to the elements. I have looked around and have found 10" galvanized 26 gauge adjustable elbows and a 60" straight piece for a reasonable price.

I also understand the off gassing of the galvanization during the heating process this would be a concern until it is gone, this is an outside operation with lots of ventilation.

My question is, if used temporarily until my permanent set up is built 2-3 seasons will there be a fire hazard using this product.

Set up: Place an elbow at the top of the first section from the evaporator, then run a 48-60 inch section of galvanized pipe horizontally, then place an elbow and run the rest of my stainless steel pipe. I also know I would need to support this setup in several locations.

In normal stove pipe it would run $300 vs. $50.

Thoughts?

[SmellsLikeSyrupNH]

I used galvanized for multiple seasons, it works, but its not going to last too long depending on your heat. I have stainless now, but you should be fine.

[wiam]

I ran 10” galvanized on my 2x6 for close to 10 years. It should be fine.

[Cjadamec]

I'm not going to say its right or wrong but I used galvanized duct pipe for a flue last season and everything worked out just fine. I too am outside in the weather so there was no place for any off gassing of the zinc to collect around me to breath in.

Its not the best way to do it but it will get you by.

However you should limit any horizontal run of pipe to as little as possible, really none is better. Its best to run the flue without any 90's if possible.
4-5 feet of horizontal run is going to kill your draft and really stress that thin pipe with excess heat.

It would be much better to use (2) 22* bends and run the pipe at an upward angle to get out from under the lean to. This will result in much better draft and less thermal stress on the pipe.

[Maple River Sugar]

I'm not going to say its right or wrong but I used galvanized duct pipe for a flue last season and everything worked out just fine. I too am outside in the weather so there was no place for any off gassing of the zinc to collect around me to breath in.

Its not the best way to do it but it will get you by.

However you should limit any horizontal run of pipe to as little as possible, really none is better. Its best to run the flue without any 90's if possible.
4-5 feet of horizontal run is going to kill your draft and really stress that thin pipe with excess heat.

It would be much better to use (2) 22* bends and run the pipe at an upward angle to get out from under the lean to. This will result in much better draft and less thermal stress on the pipe.

They are adjustable and if my clearances allow I could make them 45 degree angles leaving me with only one 90 degree.

My evaporator has a AUF which would help a little, I think.

Thanks for the input guys.

[Biz]

My old half pint with an old homemade 55-gallon drum arch had 3 elbows, about 15' total stack (6" diameter cheap stovepipe), and there were often flames shooting out the top of the stack when stoked well. Had a 6 ft horizontal run. I'm sure it was terribly inefficient, and I wouldn't recommend that you design it that way, but it had a really good draft - maybe due to the length - and I got a good boil on it even with all those elbows.

Dave

[maple flats]

A couple of things, I doubt that anyone with a stack over 4' ever get flames from in the fire coming out the top. What you see when there is a flame at the top, is wood gases re-igniting as they get more oxygen, having used up the oxygen in the firebox. It exits with enough heat and ignite again.
My first 3 evaporators came with galvanized stack. As far as a fire hazard, just make sure you have the stack far enough away from combustibles or have it protected. From wood the stack should be 3' away. You can cut that distance in a few ways. A layer of tin, spaced 1" or more cuts that in half, a second layer spaced another inch cuts it in half again. Another way is to either use insulated stack where it will not be 3' from combustibles or insulate it. To insulate you can use ceramic rigid or bat insulation, 1" then gives you 2" clearance, 2" gives you 1/2". Another way is to make your own triple wall pipe. I did that on 2 evaporators. On each I made spacers out of tin to hold the next layer at least 1" away. On mine I made the spaces 1.5". Thus on my 3x8 when I set that up, it had a 12" stack, the next pipe was 15" and the outer pipe was 18". The spaces between them were left open to allow the heat to get up and out. I now have my 12X stack insulated with 1.5" ceramic blanket and that is covered with a light gauge SS pipe. That outer pipe is suspended from the rafters using light weight chain and the bottom is slit every 1" all around 1.5" deep and those tabs are then folded inward to protect the bottom of the blanket. Any of those ideas will guard against fire if done correctly.

[Maple River Sugar]

Just for clarification this is heat duct pipe which is galvanized. The gauge is 28 normal single wall stove pipe is 26 gauge.

[Maple River Sugar]

Just for clarification this is heat duct pipe which is galvanized. The gauge is 28 normal single wall stove pipe is 26 gauge.

I think it would be best to just reduce from 10" to 8" then make the run and then open it back up to 10". That way I stay with actual stove pipe.

Thanks