Solving a problem with smoke from my arch

[renaissanceman]

Hi:
I'm having trouble with smoke coming from under the pan and any little crack in the arch bricks etc. on high humidity days. I built an arch in 2011 from an old wood stove as my firebox and cobbled together an arch. There has been a lot of warping and twisting over the last four years. The fire box is 21 inches and it rises to a 6 inch bed that is 2 feet long before the stack for a total six foot long. The slant area is approximately two feet. The whole area is lined with ceramic blanket and firebrick. I took out the baffle that is in the attached pictures at the back before the stack. The smoke stack is 9 feet above the five foot stack. I added forced air but I'm sure the way it is blowing it now comes in at the fire level and not from underneath. When we open the door to fire every 20 min. it seems like we just lose the rolling boil. I do shut down the fan when firing. Any advice? Maybe it's time to just buy an arch and admit defeat.1032910330

[maple flats]

Do you have a gasket on the arch rail, to seal the pans from the arch? I don't see one. Get either the cheap method and lay a layer of ceramic blanket, usually about 2" wide and maybe 1/2" thick before compressing under the weight of the pan. Or use the longer lasting method and buy the woven gasket sold by the evaporator companies to seal.
Then the next question, what diameter is the stack, above the base stack, it may need to be bigger. When I had a 2x6 it used a 7" stack and that was OK, but most now days sport an 8" and some even a 10" stack on a 2x6. You may just need more draft. In the short run, try the gasket andthen add some more stack on top of what you have. I suggest you use lighter weight to test it, then if that correcdts the issue be sure to change over to 24ga or heavier (lower number). If that fails, cut your base stack to where it is 2 or even 4" bigger (but not over 10") and replace the whole top portion, to add up to a minimum of 12' total, counting the base. The stack minimum is 2 times the pan length.

[Schiefe4]

Do you need to shut down the fan while firing? I have read others do not shut down the fan.

Are your firebricks mortared into place? Looks like you have gaps in your fire brick.

Why is the arch warping if you have the steel protected with ceramic blanket and firebrick?

You can pick up a high temp caulk at Lowe's (1300 F I believe). Use it to caulk the seam around the outside of the arch rail and sheet metal.

[renaissanceman]

Hi: Thanks for your response. I do use a 2 inch flat gasket under the pan. But every year it gets hardened and compressed. I think you may have put me onto something with the stack. I have 11 1/2 feet of 8 inch chimney, but when I welded up my arch I didn't figure in the 2 1/2 inch for the fire brick so the back of the 10 inch x 20 stack pipe is reduced by the width of the brick. I do know if that does something to mess up the air flow or not. I messed around with the forced air today and I think I have been blowing in way too much. I have a 10 inch squirrel cage blowing without any reduction right into the ash pan. Schiefe4 asked about mortaring the bricks and calking the top edge which I will do. I think I need to skim the whole inside of the bricking to fill all the gaps after caulking. I may have to weld a piece on to extend the back of the arch and move the fire brick to the out side of the back steel to create a full 10 inch wide space. All the warping is going on in fire box above the fire brick. The steel plate just dissolves where it is not bricked in the top 12 inches.

[Schiefe4]

Why isn't the top 12" around the firebox bricked?

[maple flats]

I don't think the gaps in the brick, nor the brick reducing the width are causing the smoke leak. With the size you say, just try adding 2 ft at a time to the stack height. You just need more draw.
The gaps may cause heat damage, but not smoke leaking.

[mellondome]

With forced draft/air under fire, your stack height will not matter. I have a 2x6 with a 465cfm blower attached to the ash box with no resteictions.... and a 1hp dust collector providing air over fire.. no smoke anywhere. Even before the aof... I would only have smoke leaving the stavk after firing... nothing inside the building.. my arch is blanket lined with brick loose fit in the firebox. I fire every 5-7 min depending on wood and weather. 8" stack with a restricted entrance.

You will lose the boil because you are drafting cold air across the bottom of the pan when you open the door/s to fire.

I use blanket to line my rails under my pans and to fill the gap between the pans.

Where it smokes, you have a gap.. and your fire either is not hot enough or doesnt have enough air.

[Super Sapper]

If you have blanket you do not need the firebrick by the stack. It is only needed where the blanket can get damaged by adding wood or cleaning the bottom of the pan. Adding more height to your stack will increase your draft for natural draft but will add resistance in forced air. I would caulk where you know it is leaking and try reducing your air some.

[Flat Lander Sugaring]

all good advice above but no need to shut down fan where good welding gloves and long sleeve shirt. only keep door open long enough to put what wood you have in hand inside close door, then grab another arm full if needed open door back up etc.

[mellondome]

What are you using for wood? How dry? What size is it split to? If I waited 20 min to fire... my fire would be out!

[Sugarmaker]

First DONT give up, your almost there!
Lots of good suggestions too!
Your arch looks great! I am not sure where you have the dissolving steel problem above the brick? Looks pretty well bricked to me and should hold a fire real well. I will say since I have been there that the steel you have going across the arch will not hold up long and is not needed. It will not take the extreme heat and will do a melt down! Have you replaced it more than once? Looks like grating. Is that to support the pan?
Anyway I think you hit on your problem, You may need to control/ damper the air from your blower. Either with a damper or speed control or both. You may be adding just a tad to much air in the fire box. You should dial it in so that you can open the door and not have it belch fire out at you with the blower running. Fire the rig close the door and should not loose much boil.
Your stack sounds right sized and height for the size rig.
Don't give up!
Regards,
Chris

[Flat Lander Sugaring]

What are you using for wood? How dry? What size is it split to? If I waited 20 min to fire... my fire would be out!

they say size of your wrist my a little bigger like bicep (which is still pretty small haha) perfect wood one year in arch I was going 9 to 11 minutes, but most of time my wood to dry so usually around 6 to 7 minutes. I can throw iced logs in my unit and they will be devoured in a matter of minutes.

[maple flats]

I can throw iced logs in my unit and they will be devoured in a matter of minutes.
While you may be able to throw iced logs in your arch and have them be "devoured" in minutes, that cost you thousands of potential BTU's. Wet wood will not burn until the heat has evaporated the moisture and the heat needed to evaporate the moisture could have been used to heat the pan. Being the fire is not in a pressurized environment, the steam generated can not go over about 220 F. That moisture must be driven out before the log can generate heat enough to boil the sap effectively.

[Flat Lander Sugaring]

While you may be able to throw iced logs in your arch and have them be "devoured" in minutes, that cost you thousands of potential BTU's. Wet wood will not burn until the heat has evaporated the moisture and the heat needed to evaporate the moisture could have been used to heat the pan. Being the fire is not in a pressurized environment, the steam generated can not go over about 220 F. That moisture must be driven out before the log can generate heat enough to boil the sap effectively.
i understand what your saying but to the human eye there is no change in the boil, and hope to finally add temperature probes to arch this year.

Also with small arches people who add AOF just pipe in outside air at what ever temperature it is. I preheat my AOF which makes a huge difference from some one introducing 36F air to some one introducing 600-1000F.

Like Laps force 5 4x14 stack temp is around 720-780f but at rear of arch its 1900f where did that 1200F go? reintroduced into arch via AOF (I believe).