Cinder block evaporator design

[ShaunG]

So I have been using this arch for several years. I recently had to move its location. So I figured I take some pictures and see if anyone had some tips on its design.

It is not cemented. It fits 5 full size chafing pans. And near the stack I put a cheaply stainless steel stock pot that acts as a Sap warmer. In the middle I place cinder blocks to take up the interior space. (Not pictured) I will back fill the spaces on the side of interior cinder blocks with some dirt and gravel. Then at the front interior block I will use the dirt and gravel to create a slope. And I line the whole thing with fire bricks. In the very front ,the fire box, I do cement the fire bricks up the sides. Finally I use a fire place grate. I use mostly pallet wood and some tree wood. The chimney also has a damper.

Good air flow is achieved. And it gets HOT, enough to melt the fire place grate.

But I never seem to get good Evaporation rate. Or at least as good as I think I should.

So what does everyone think? Any tips or advice to make it better?
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[ShaunG]

2 more photos
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[ecolbeck]

Two things come to mind
1. Where is the air intake? Ideally air would come in under the grates.
2. How much space is there between the ramp and the bottom of the pans? The space should be minimal, a couple of inches at most.

[ShaunG]

There is a slider vent on the door, but mostly I prop door open.

The distance between pan, (just eye balling from memory. Is probably 5 to 6 inches.

[ecolbeck]

Running the evaporator with the door open will definitely slow down the boil. Cold air should only enter directly under the fire. Raising up the front plate so that air can enter underneath could be a simple solution. The picture below (kinda small, sorry) shows a front plate raised up on a concrete block with a cheap bathroom fan blower directed through opening in the block.

Building up the ramp to within a few inches of the pans will help a tremendous amount as well.

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[ecolbeck]

Looks like you might have a damper installed on the stack? I would remove that. There shouldn't be any flue restrictions. Hope this helps. Be sure to post how it goes.

[tcross]

just a quick thought. you could turn the blocks on the bottom row under your fire so they let in air. i'd guess that'd get your fire hotter?

[Swingpure]

Has anyone ever tried pouring concrete and have solid concrete walls, instead of cinder blocks for their evaporator?

[tcross]

never tried it, but my grandfather did. he built his sugarhouse into a bank. he dug out the bank and poured the concrete into the bank the size of his pans. poured the ramp, sides etc all in solid concrete. if i remember correctly, the walls were about a foot thick. i have no idea if he put any insulation stuff in there or not, but it's still standing and there aren't any cracks. i'm 39 and that concrete arch was built well before my time!! the sugarhouse is only used as a sap collection sight now, by my parents neighbors. So, i'm assuming it can be one!