Switching from steam pans to divided - help with evap modifications

[Openwater]

Got it. Finally starting to understand the thermodynamics. I've used wood in a wood furnace to heat the house before where I wanted long-lasting hot coals. With the evaporator, however, it sounds like we don't want just hot coals, but flames stretching as far thru the arch as possible, correct?
Last night, I welded-up some steel braces/brackets(old bedframes) to set in the arch to hold up the cementboard. Will fill the space underneath with mineral wool/insulation or vermiculite.
Any advantage to putting a skim coat of refractory cement on the cementboard? I've got a small bucket of the premixed stuff.

[Pdiamond]

won't hurt a thing.

[Openwater]

Did a test boil on my new/first divided pan yesterday (14" x 48") which is 18g stainless. Didn't get the hard boil I was hoping for. Here's my questions after test boil:
1. Is it normal to have little to no boiling in 1st channel coming from float box? I did get some boiling in 1st channel, but mainly in front of pan right over firebox.
2. Front of pan definitely boiled better/harder than back of pan, so I need more heat in back of pan. Planning on laying a piece of 2" angle iron or something about 2/3 of the way up the ramp to try to force more heat up under back part of pan.
3. Could I use a stronger/better blower for my AUF? Right now I just have a bathroom exhaust fan (100cfm) blowing thru a 4" duct into ash space under grate hooked up to a dimmer switch used for ceiling fans to control fan with 3 different speeds; I assume I get the 100cfm at the 3rd/highest speed.

Last year I boiled in restaurant steam pans that I think were only 22 gauge and the whole pan sat down in the arch so sides of pan got scorched; those pans produced a HARD rolling boil. The new divided pan did produce ALOT of steam when boiling so I couldn't even see the water surface or bottom of pan, so I'm not sure if my expectations are too high. I would really just like to make sure I get enough heat/boil to create the sap/syrup gradient and I don't know if that may be impossible if the back of the 3 channels isn't boiling as hard as the front of the channels.
Thanks for any advice or suggestions.

[Cjadamec]

I would try more air first. I did the exact same thing as you going from 6" steam pans to a proper syrup pan.

I ended up raising the floor of the evaporator with brick and ceramic blanket. It was just what I had around at the time.

You don't need the whole floor raised that high. I went with a "wedge" floor where the floor just slopes up to it's highest point for the last 6" of pan length. That last 6" has about 2 inches of clearance. I run an 8" stack. Just after the pan the flue spaces opens right back up and out the stack it goes.

If you have any inflatable lawn ornaments those can be a good source of fans in a pinch. They generally have good cfm and are positive pressure blowers.

[Pdiamond]

Openwater, what kind of space do you have under your pan from where the ramp begins? You only need about 1/2 to 3/4 of an inch under the pan in this location, then just before it exits the arch have a drop.

[Openwater]

Openwater, what kind of space do you have under your pan from where the ramp begins? You only need about 1/2 to 3/4 of an inch under the pan in this location, then just before it exits the arch have a drop.

Maybe that's my problem. Front of ramp right after firebox is about 7-8" under the pan and then ramps up to about 2.5" under back of pan before opening up into the bigger space in stack before hitting 6" pipe.
I thought I always had to keep at the least the same space/area under the pan as the cross-sectional area of the 6" stove pipe. I didn't know if it was ok to "choke" the opening under the pan to an area smaller than the flue pipe.

[Pdiamond]

I believe if you narrow that space you will achieve the boil you want. Ceramic blanket works well for this.

[Openwater]

I measured it. front of ramp right after firebox is 4.5" from pan and ramps up to 3" from pan before entering stack.
If I put in a firewall right after firebox that goes up to 2" from pan, would I still need to fill in the space after the "wall", or will the flames stay up against the pan bottom for the length of the pan?
I don't have much time for fabrication at this time since I plan on boiling sap this coming Sunday.

[Cjadamec]

I measured it. front of ramp right after firebox is 4.5" from pan and ramps up to 3" from pan before entering stack.
If I put in a firewall right after firebox that goes up to 2" from pan, would I still need to fill in the space after the "wall", or will the flames stay up against the pan bottom for the length of the pan?
I don't have much time for fabrication at this time since I plan on boiling sap this coming Sunday.

I would simply lay 1 course of brick under the back edge of the pan. That will bring the gap down to 2 inches or so right at the back of the pan and give you more heat there.

That's a quick and easy way to do it and should get you results right away. There is no need to alter the rest of the ramp.

[red/one]

I used vermiculite and ceramic blanket last year and it worked very well. If you build a wall to 2" or so below the pan you can fill behind it to the stack.