how do I get more of a boil in the rear flue pan

[grimmreaper]

I have a 7'x30" rear flue pan(raised ).it was bricked to half way of the flue pan,and I het great boil in the front.what I need is more boil in mid way of pan & towards the rear .any ideas ?

[West Mountain Maple]

refer to this thread - http://mapletrader.com/community/showthread.php?16652-Common-Evaporator-problems-and-their-solutions

[PerryW]

Does it have a ramp just behind the firebox that slopes upward and almost touches the bottom of the flue pan. This forces the fire up into the raised flues?

You can also open up the damper more (if it isn't already)

You also may need more draft (taller stack or bigger stack diameter)

You could also try burning longer wood, or chucking some wood further back.

[Brent]

with 3 different evaporators over 6 years and various combinations of blowers over and under the fire, I've never seen anything like a uniform boil front to back.
About 80% of the boil is in the front 25% of the pan.

If you find a way to make it boil everywhere, please let me know.

[Maplewalnut]

I like Brent have fiddled with my rig for a couple years. Sloped the ramp more, sloped it less, 6 inches from stack, 12 inches from stack. Vermiculite is almost touching the rails so heat is getting pushed up in my raised flue. Nothing seems to help. I have gotten it to the point where the front third of my back pans rips and the boiling bubbles just sort of flow backwards. Best I can do. I may add a section of stack next year but it is already about 24 feet high...

[Brent]

I think what is really going on is that the front gets the most heat, boils up, sap flows to the back on the surface then descends into the flues near the back and starts flowing forward. As it goes forward it boils again. I think it will be nearly impossible to make the whole pan boil without pumping in HUGE amounts of heat ... most of which will go up the stack.

[PerryW]

I wouldn't worry too much. If the very back of the flue pan is a full raging boil, then you are losing a lot of heat up the stack.

[Big_Eddy]

One thing I've done that seems to be helping a bit is I placed a firebrick on its side at 90 degrees to the arch, right behind the last flue in the center of the arch. It forces the gasses to go around (outside) before going up the stack and seems to be making the sap boil just that bit better at the back of the pan. What was happening before was I would have a good boil all the way down my middle section, but not in the 2 outside sections. Now I get a more even boil in all 3.

But the front 25% always boils a lot stronger than the rest of the flue pan.

[grimmreaper]

Thanks for all the help guys.my firebrick waas lined in a slant to half way of the rear flue pan.so I added brick to force the flame to the front and carry to the rear .I have 22 feet of stack so I have great natral draft.

[sam1234]

Hi,

As it was said before, the draft is the key to the right ''hot spot''.
Low draft will keep the flame towards the front.
Hi draft will bring the flame towards the back.

If you inject air in the chamber, it automatically decrease the draft.
Cut a little bit of air and it will bring the boil towards the rear.

You can purchase a Magnehelic and do some test with the damper or air or adding stack... you'll see how important it is...
Good luck.

Sam1234