Need some help on New 2x6

[mol1jb]

Hey all,

Just did my second boil on my new 2x6 raised flue evap. I am loving the step up in boil rate however I am a little disappointed with the gph. After 2 boils I have hit between 15-17 gph. I feel that is a bit under what this rig should run. I'll detail what I have done so far and if you could chime in with ideas I would appreciate that.

I'll detail the evaporator first. It is a 2x6 with hood with 2x4 raised flue back pan and 2x2 4 compartment front pan. No preheater. It has AUF and preheated AOF. Blower is a 1/2 horse bouncy house blower. Fully insulated and fire bricked around the fire box. So at start up I an running around 1 inch in both front and back pan. It usually takes me close to an hour to get everything running consistently around 1k stack temp. That is where I have been maintaining my heat. Firing every 10 minutes with 3 pieces of fist sized wood and the stack usually goes up to 1.1k and at refires around 975. Outside stack is always no visible smoke, even on reloads. Let me know if you need more info.

I know not having a preheater will drop my gph some but it seems like most are running 20-30. Is there anything obvious that I am not doing? Or is my current gph in line with a 2x6 with no preheater?

Thanks for the help.

[n8hutch]

Is your hood drafting good? Any chance that you have condensation dripping back into your pan? How hard does the back pan boil? What kind of a gap do you have between the flues and the arch bottom? It sounds like you have plenty of heat going up the stack. Is that an internal stack temp ? I almost think you could scale back the blower a little.

I would also run the flue pan closer to half or even a quartet inch, often when mine is boiling real hard I will See flashes of stainless steel, I usually adjust the float a touch when that happens.

[Russell Lampron]

How deep are the flues in your flue pan? How much space do you have between flue pan and the bricks or filling in the back of the arch? It should be filled right up to the rails to force the flames and heat up into the flues. If your flues are only 3" to 5" that will give a lower gph than if they were 7" or more. With no blower or hood I was getting 25 to 30 gph with my 2x6 raised flue with 7" flues. I was firing every 8 to 10 minutes and kept no more than 3 layers of wood on the grates. I added a hood and preheater and got 30+ gph. I than added an auf blower and got 35+ gph. My firing interval was still the same but I was filling the firebox to the bottom of the pan. I then added a bubbler and was in the 40+ gph range. This year I bought a new W F Mason airtight arch with auf/aof and don't yet know what I'm going to get for gph but when I did a test boil the flue pan boiled better than I have ever seen it boil. I'm hoping 50+ gph!

[maple flats]

That is far under what a 2x6 with 4' raised flue will give. Start at 1" until you get used to using the pans but then gradually reduce to 1/4-1/2" over the flues. When firing, you are not putting enough wood in. Mine is a 3x8 but I add 2 arm loads every 9 minutes if taking my time and if pushing it I do 2 arm loads every 8 minutes. I also have AOF. I don't think you are putting enough air in the AOF, my stack temp usually runs between 700-850, but without the AOF it used to run at 1200-1500F. How are you distributing the AOF? do you have a nozzle every 6" from each side of the fill door, down each side and across the back wall (of the firebox) and have it aimed down about 15 degrees and at the opposite side of the fire. That way, you burn the gasses under the pans. With just 3 sticks at wrist size every 10 minutes and you get stack temps of 1000 it says you are not putting the heat into the pans. How much space do you have from the bottom of the flues to the "floor" bin the arch? That should only be about 1/4", too much space and the heat is not pushed into the flues where it can boil the sap harder.

[maple flats]

You should be able to get 30-35 GPH once all is right and you get the depth to about 1/4" over the flues

[mellondome]

Way low on the wood . When I burned wood on my 2x6 .... i used 5 pieces of wrist size (not fist) wood every 5 to 7 min. 5 with aof. How you have the arch configured will make a huge difference on your boil rate. But even with a botched arch build you should be getting 25-30 without a hood.

[mellondome]

For your arch with auf, you will want to block off the first and last 6" of your grates. This will stop the cold air from bypassing the fire and going directly to your pans. Your ramp should meet the bottom of your flue pan 18" back. The fill under the flue pan should almost touch the flues. The transition out the back of the pan should be the last 4" of the flue space.

[mol1jb]

Is your hood drafting good? Any chance that you have condensation dripping back into your pan? How hard does the back pan boil? What kind of a gap do you have between the flues and the arch bottom? It sounds like you have plenty of heat going up the stack. Is that an internal stack temp ? I almost think you could scale back the blower a little.

I would also run the flue pan closer to half or even a quartet inch, often when mine is boiling real hard I will See flashes of stainless steel, I usually adjust the float a touch when that happens.

Hood is drafting good but sometimes some steam sneaks out. It has gutters all around and a drip tray under the hood pipe. If I had to describe the back pan I would say front half is a raging, rolling boil and the back is a strong boil. The stack gauge is a probe.

[mol1jb]

How deep are the flues in your flue pan? How much space do you have between flue pan and the bricks or filling in the back of the arch? It should be filled right up to the rails to force the flames and heat up into the flues. If your flues are only 3" to 5" that will give a lower gph than if they were 7" or more. With no blower or hood I was getting 25 to 30 gph with my 2x6 raised flue with 7" flues. I was firing every 8 to 10 minutes and kept no more than 3 layers of wood on the grates. I added a hood and preheater and got 30+ gph. I than added an auf blower and got 35+ gph. My firing interval was still the same but I was filling the firebox to the bottom of the pan. I then added a bubbler and was in the 40+ gph range. This year I bought a new W F Mason airtight arch with auf/aof and don't yet know what I'm going to get for gph but when I did a test boil the flue pan boiled better than I have ever seen it boil. I'm hoping 50+ gph!

I believe they are 7”. Its a leader lead free soldered

[mol1jb]

That is far under what a 2x6 with 4' raised flue will give. Start at 1" until you get used to using the pans but then gradually reduce to 1/4-1/2" over the flues. When firing, you are not putting enough wood in. Mine is a 3x8 but I add 2 arm loads every 9 minutes if taking my time and if pushing it I do 2 arm loads every 8 minutes. I also have AOF. I don't think you are putting enough air in the AOF, my stack temp usually runs between 700-850, but without the AOF it used to run at 1200-1500F. How are you distributing the AOF? do you have a nozzle every 6" from each side of the fill door, down each side and across the back wall (of the firebox) and have it aimed down about 15 degrees and at the opposite side of the fire. That way, you burn the gasses under the pans. With just 3 sticks at wrist size every 10 minutes and you get stack temps of 1000 it says you are not putting the heat into the pans. How much space do you have from the bottom of the flues to the "floor" bin the arch? That should only be about 1/4", too much space and the heat is not pushed into the flues where it can boil the sap harder.

My AOF is basically the Proctor guidelines except for 1/4 in pipe for nozzles. I had been running my AOF at 100 and AUF around 45 percent. Under the flue pan is touching at the back of the firebox and close to 1/4 under the rest of the way.

[mol1jb]

For your arch with auf, you will want to block off the first and last 6" of your grates. This will stop the cold air from bypassing the fire and going directly to your pans. Your ramp should meet the bottom of your flue pan 18" back. The fill under the flue pan should almost touch the flues. The transition out the back of the pan should be the last 4" of the flue space.

My flue pan is almost half exposed in the fire box. I will have to check the back transitions out of the flue pan. And lower the sap level in the back pan. With adding more wood per loading I feel I will have to turn down the air as my stack temps seem to be high for an aof.

[mellondome]

I have the same pans. When I burned wood I didn't use a stack temp. I wanted to boil as fast as I could. Most nights if I turned out the sugarhouse lights there would be a glow to the bottom of the base stack. Lowering your levels, especially in the back pan will help a lot.

[Russell Lampron]

Filling the firebox when you fire will help too. More wood equals more flames and more even heat distribution. Turn down your blower and see how that goes. The guy that built my arch set it up so that 25% of the air goes under the fire and the other 75% goes over. Mine uses a single blower and the air over part of it blows through the arch front only.

[mol1jb]

Thank you for all your advise. I was able to boil today at 25 gph. Over the past few boils I have reduced pan levels to around 3/4 in. The drip tray of the hood was also condensating on the under side and dripping into the flue pan. Fixed that. I have loaded with more wood and turned down the air to 75% over and 20% under. Loading still every 10 minutes with 5-6 pieces depending on stove pipe temp. Today it was 900-1k and that was working well.