Fan and airflow issue on my home made evaporator

[SmellsLikeSyrupNH]

Hi Everyone,
Any advice is appreciated!!

Got my evaporator this weekend and boiled with it to test it out on Saturday and Sunday. I found that no matter how much I kept the flue open on the front of the door that I didnt get enough air to keep the fire hot, I got a much faster boil opening the door almost fully as opposed to keeping it closed. I ended up removing the flue on the front entirely and that didnt seem to help much either. Keeping the door cracked was my best option. Fully open was my best result. The inside of the stove is fully lined with brick and blanket and I have a pretty tight seal between my pan and the top of the stove.

Im guessing a fan/blower is my best option for keeping the fire burning hot while still keeping the door closed. Does anyone have any other thoughts on this? Pix attached to this message so you can see what im working with. Also anyone know where I might be able to find a blower that I could mount to that front opening?

Thank you!!
-Scott
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[TunbridgeDave]

Is the stack tall enough? Do you have an idea of your stack temp?

[maple flats]

The stack should be at least twice the length of the pans total. If that is not enough, add more, in 2' increments. How are you firing the arch? You should use dry wood, split wrist sized and refuel every 7 minutes. At the initial fueling and each refueling, fill to within 6-8" of the pans. If you criss cross the wood it burns best, especially until you have a full bed of hot coals. Refuel by the clock and have the door open as short a time as possible.
Most likely the issue is stack height.
That looks like an old Shenandoah stove. If it is, you must alter it some. They were super tight very efficient stoves, but not really suited for boiling sap. You need more air inlet. You need to be able to open a draft door that is about 60-70 Sq. inches, and it feeds the air under the grates. The air inlet I see looks like maybe a 4"-5" hole, far too little air to burn like you need it to.

[maplehick]

Scott, on my first block arch I put a small blower from a old boot dryer In the door. I think it was 2in pipe. Mite work?

[bowtie]

If you use a blower your stack height should not matter except you will want it high enough that if the wind shifts it will not blow back in your face or drop debris in your pans. A small blower and rheostat would help, also it looks like your wood is quite "wet" , this would cause you to have the door wide open to get a hotter burn,if can not get dry wood I would look into a blower, personally even with dry wood I would look into a blower, it will help get your boil going a lot faster and allow you to maintain an even fire with regular loading.mixing in pallet wood if available will also help.

[bowhunter]

With or without a blower the stack has to be high enough to generate enough draft to keep the arch under a slight vacuum otherwise you will get smoke out every leak and the door when it's open. That's just physics.

[SmellsLikeSyrupNH]

Thanks Everyone….Id have to say my stack pipe is 6ft tall….certainly not double the length of the pans…as for the wood, the pix are from Saturday when i was just testing with some wood i had around the yard, on sunday I boiled with dry pine and it did burn a lot better and hotter. I had a delivery of seasoned wood on Sunday and used that. So the fire actually draws in oxygen through the stack pipe? I didn't assume anything flowed down it with the smoke coming out of it. Hmmmm I don't see a way where I could create a bigger opening to allow more air flow except to leave the door open, OR get a blower…the boot dryer idea sounds ideal but the task would be finding one…The opening on the door is probably 5" diameter and that is the only available air inlet I have in this stove.

I didn't realize the stack was so important….I just went out and measured, it is 5ft tall, and 7" diameter. My pans are 24x46" for my back and a 24x24 on the front….I am going to see if there is a way for me to open the holes in the grate on the bottom a bit more. I really would rather not keep the door open, so if extending the stack doesn't solve the issue, i guess a blower is my only other option?

Thanks again!!

[bowtie]

What law of physics would that be? Hot up and cold down? If you draw air down your chimney you have a serious problem as air should always be drawn in under the fire through a draft door. In the wonder wood stove I use at work I can open the bottom pan door and keep the upper door open and have little if any smoke ever come in the door as long as it is burning hot. In a tight system with blower you stack doesn't matter as air will naturally be forced up. Get enough air in your draft door and keep your pan sealed to your evap and the fire will chase up your stack up whether it is one foot or twenty.