Adding secondary air tubes to 1500 Hotblast

[BruceMilo]

I have heated my house in central Nebraska for 19 yrs solely with a USSC 1500 Hotblast wood stove. It has done me well, I have seen people on here reference it as a wood hog, but I have nothing to compare to, so maybe it is. I have been exploring ways to improve efficiency, I am going to add secondary air tubes to see how that works. I have read a few threads a few years old that some have modified this exact stove, would like to know how that is working out over the years. I'm using 3/4" pipe, my questions mostly is:
1 How many holes for air, and what size of holes?
2 Is there a need for air regulation on the air tubes being installed?
3. Has anyone had a dangerous situation with a stove getting too hot, warping steel, or burning through?

If anyone has any general input on these questions, if you have done these mods before to stoves, I would love some input. More burn time and more heat out of the wood is always a plus, if I can achieve that then I'll call it a win.
Thanks, Bruce

 

[aokpops]

Bruce if you get it right it will burn very hot . Just make sure to beef it up to handle the heat . Was looking in the stores about all the new stoves had tubes . Maybe a retro fit could be found ?

 

[BruceMilo]

Manufacturer said no mods available other than an induced draft kit, dont think that's what I'm after.
I will be running the air tubes under a baffle above the fire. This baffle is plate steel only, I planned on setting firebrick on top of it to absorb heat from the baffle. Or is that going about it backward, the brick should be between the fire and the steel?
The stove has firebrick lower in the chamber where the coals would be, but any secondary burn would be adjacent to exposed steel of the sidewall of the stove. Not sure if I need to do anything there?
Another thing there is no window on the stove, I wont really know what is going on in there. I dont like that.

 

[Bobby Kirbos]

My fireplace insert has reburn tubes. Enviro uses some sort of heat resistant material that must have come out of the US space program. It's about 3/8" thick and super light, but about as strong as cardboard. If you can find it, it might be easier to design around than fire brick.

 

[BruceMilo]

Hey, there's an idea. Have you ever worked with cement board, used for backing for showers, or for subfloors when you tile? It wouldn't be cement board in your stove, would it? That would be easy to work with for sure. It wouldn't have the mass of brick, but might be enough to keep direct flame/heat off of the steel. Hmmmm.

 

[Bobby Kirbos]

Hey, there's an idea. Have you ever worked with cement board, used for backing for showers, or for subfloors when you tile? It wouldn't be cement board in your stove, would it? That would be easy to work with for sure. It wouldn't have the mass of brick, but might be enough to keep direct flame/heat off of the steel. Hmmmm.

It's not cememt board.
https://www.amazon.com/Lynn-Manufac...locphy=9006623&hvtargid=pla-474941865826&th=1

Google "superwool fire board".

 

[BruceMilo]

I see, thank you. Have anyone ever worked with it, can it be cut to fit, or not so much?

 

[BruceMilo]

Googled it, can be scored and cut with a knife, or use a hacksaw. Thanks!

 

[BruceMilo]

I dont know.... if it doesnt work I'm not out much.

 

[brenndatomu]

Hey, there's an idea. Have you ever worked with cement board, used for backing for showers, or for subfloors when you tile? It wouldn't be cement board in your stove, would it? That would be easy to work with for sure. It wouldn't have the mass of brick, but might be enough to keep direct flame/heat off of the steel. Hmmmm.

Ceramic fiber board is what you want...and that black iron pipe will last a couple months...need to go stainless if you want longer life than that. Good enough for the first round of testing though, there are always lots of changes made before its over...and its never over

 

[Bobby Kirbos]

Something else to consider in your design,

In my stove, the fiber board is angled up toward the smoke outlet from the fire box. See attached sketch (side view of stove). I'm no expert on the subject, but I suspect they did this for a reason.

 

[BruceMilo]

I figured the same, trial run with black pipe, then if I think it's worth it, I'll rebuild it with stainless before next season.
And thanks for the sketch. I have steel baffles lying flat in my stove, which the tubes I installed are running directly underneath. I left enough space to insert a fiber board between the tubes and the existing baffle. The baffles come out, I could wedge the baffle up in the front, along with the fiber board, to give it an angle like your sketch. Wonder if it aids in getting the exhaust to roll out of the chamber easier. More to ponder....... In the meantime I have my gas furnace running, which I do not like!