Hottest part of firebox

[clw]

I have 2x4 flat pan with 3 channels. The firebox slopes up to the chimney at the back. Does anyone know whether the front or rear is the hottest part of the pan and firebox?

The sap is input at the rear and drawn off at the front. Has anyone reversed this and drawn off at the rear? Is there any reason not to try this?

I am having excessive niter build up at the drawoff. The pan is physically turned around every boil and cleaned if appropriate.

Any and all comments and advice would be appreciated.

[treehugger89]

The front of the arch should be the hottest or were the pan sits over the firebox. Try to level out the pan, this may help with the niter.

[TreeTapper2]

What type of Maple tree are you tapping?

[clw]

We're tapping sugar maples, sap runs close to 3%. We have discovered the importance of leveling the pan and have made a greater effort to insure the pan is level.

[treehugger89]

How long in between time do you refuel?

[clw]

We have a timer and fire 3 sticks every 6 minutes. The sticks are mostly ash, split small, arm size. We usually have a good boil everywhere except by the end of the day we have foam at the drawoff instead of small bubbles. It's niter buildup and then we clean the pan after the next shutdown. We're wondering if we should have a slower boil at the drawoff, maybe drawoff at the rear instead of the front?

[treehugger89]

What's the temperature you drawoff at? Should be around 217 degrees.

[clw]

We shoot for 219, then use a hydrometer. Subsequent drawoff temp is adjusted by the first hydrometer reading. Niter and foaming in the drawoff channel affect later temp readings so we're frequently using the hydrometer to adjust subsequent drawoff temps.

[Super Sapper]

You can try running it the opposite way but your niter is probably a result of your sap makeup. I end up with "corn flakes" in the last channel every 300 to 500 gallons depending on the year boiling raw sap.

[treehugger89]

The temperature you drawoff will often change day to day. If you have a barometer you could calculate what temperature you drawoff at.

[clw]

I had not heard the term "corn flakes", but I think I have them. Is that niter that has started to harden at the drawoff? When we turn the pan around we do some light scraping at the old drawoff and white flakes break off, we scoop them out with a small fish tank net.

Instead of a barometer and calculations, we use the hydrometer for the first draw each day and use the corresponding temp as a guide for subsequent draws. But we do find that when the syrup is foaming and there is lots of niter, if we wait for the temp then the syrup is way overdone. So we start testing before the target temp is reached. Does anyone else see this phenomenon?

[dcast99]

I do the same as you as far as adjusting the draw off temp. Each day I use the hydrometer to test the first daw off and then figure at what temp to drawwoff at. Some days it may be at 6 others it may be at 8. A little foaming is normal. It usually is only a problem when the foam begins to reach the the middle of the partitions. A drop or 2 of defoamer solves that problem. If the evap is ramped correctly, the back of the arch should be the hotest and boil the most. It needs to be that way because that is where you need to get rid of most of the water. The build up of niter is also normal and it can vary from yr to yr and also from beginning of season to end. That is what the filters are for.