Fire box length and ramp for raised flue.

[KReinisch]

I have a 30x8, with a 6 foot flue pan. It sits on a leader arch. The arch has a long fire box. I am assuming its for there older set ups that had 3 foot syrup pans. My question is... where should the ramp meet up under the flue pan. Right now it is about 1.5 to 2 feet into flue pan. I hope that this is a good enough explanation.

The reason I ask... is that I don't think I am getting the boil I need out of it. I have a blower and I have put a preheater on it and I am just getting 50-60 gph.

[Sugarmaker]

your 50-60 is not bad but may be able to be improved with changes to your ramp design under the rear pan. There must be a cross section of the typical raised flue/ arch design. One of the things is to have the size of the opening at the back end sized about the same as your stack area in sq inches. This will keep a little more heat up in the flues. To much area may let out too much heat too fast. Also do you have a idea what your stack temps are? Watching those temps can be indicators of how the arch is running. I would think 75 might be a upper limit on your rig???
Just some changes in firing may help too? how often, type of wood .........??
Regards,
Chris

[Sugarmaker]

your 50-60 is not bad but may be able to be improved with changes to your ramp design under the rear pan. There must be a cross section of the typical raised flue/ arch design. One of the things is to have the size of the opening at the back end sized about the same as your stack area in sq inches. This will keep a little more heat up in the flues. To much area may let out too much heat too fast. Also do you have a idea what your stack temps are? Watching those temps can be indicators of how the arch is running. I would think 75 might be a upper limit on your rig???
Just some changes in firing may help too? how often, type of wood .........??
Regards,
Chris

[KReinisch]

As far as stack temp... I can put my hand next to it without getting hot. As for wood and firing... it has been a mix of hard wood and pine but all has been dry. I fire one door every 5 minutes.

[n8hutch]

I personally would make your firebox about 3 feet deep , followed by a vertical wall right up to level with your arch rails. Then level with your arch rails all the way back to within 6-8" of the back of your flue pan & then have it drop down to exit through your smoke stack .

Does your pan boil hard in the back?
When my Evaporator is boiling hard you can not see anything in the front panel or the back without cutting the steam with a torch.

I have mine setup as described and the sap will jump over the sides even in the Back half of the flue pan at times.

[treehugger]

I personally would make your firebox about 3 feet deep , followed by a vertical wall right up to level with your arch rails. Then level with your arch rails all the way back to within 6-8" of the back of your flue pan & then have it drop down to exit through your smoke stack .

Does your pan boil hard in the back?
When my Evaporator is boiling hard you can not see anything in the front panel or the back without cutting the steam with a torch.

I have mine setup as described and the sap will jump over the sides even in the Back half of the flue pan at times.


Do you have a pic of how your arch is set up? Or maybe a diagram? I would love to see a boil in the front and rear of a flue pan.

[mellondome]

You want your rampnto meet the flue pan 1/3rd the way back. 6ft flue pan-- 2ft open to the firebox/ramp. How you exit the gas will make a huge difference as sugarmaker stated above.
Treehugger...a properly setup arch will boil aggressively the entire length of the flue pan. The front and rear usually boil harder than the middle.

[KReinisch]

So I Have a 12 inch stack. That means 113 square inches. That means my opening should be about 4 inches. I tried doing that and I had flames shooting out of the fire door.

My pan boils hard in the front half in the middle channel and 1/3 in the out side channels.

[mellondome]

So I Have a 12 inch stack. That means 113 square inches. That means my opening should be about 4 inches. I tried doing that and I had flames shooting out of the fire door.

My pan boils hard in the front half in the middle channel and 1/3 in the out side channels.

Do you have an air tight door?

[treehugger]

You want your rampnto meet the flue pan 1/3rd the way back. 6ft flue pan-- 2ft open to the firebox/ramp. How you exit the gas will make a huge difference as sugarmaker stated above.
Treehugger...a properly setup arch will boil aggressively the entire length of the flue pan. The front and rear usually boil harder than the middle.

The front 1/3 boils great the rest not so much. Maybe I need to restrict outflow by the stack. I have it ramped halfway back in the flue pan, may I need to adjust that too. Sorry to have partially hijacked this, it seems to be a common issue.

[mellondome]

The front 1/3 boils great the rest not so much. Maybe I need to restrict outflow by the stack. I have it ramped halfway back in the flue pan, may I need to adjust that too. Sorry to have partially hijacked this, it seems to be a common issue.

Restrict the opening for the gas to to put of the pan. This will slow down the flame/gases so that they will actually heat the pan. I had the same issue when I first started boiling. Most rigs will only need about a 4in opening for the exhaust to exit the flue pan.

[KReinisch]

I do not have air tight door.

[treehugger]

Restrict the opening for the gas to to put of the pan. This will slow down the flame/gases so that they will actually heat the pan. I had the same issue when I first started boiling. Most rigs will only need about a 4in opening for the exhaust to exit the flue pan.

Thank you I really appreciate the help. I think I'm around 7-8 inches now.

[KReinisch]

So what about the flames I had shooting out my doors when I restricted.

[mellondome]

Path of lease resistance for the flame. Or it is a source of oxygen to burn. Anytime you have forced air, you want to make sure the only place for fire to go is where you want it... up through the pans. Seal up the door or turn the blower down. What size stack? How often do you clean the under side of your flue pan?