2x4 evaporator questions

[bubblinhutnh]

I have a 2x4 arch with 3 chamber flat pans front and rear. I have 12' of stack on the arch with a cap on top of the top stack. By cap I mean a lid with open sides to prevent snow/rain from getting in. \
My problem is that I can have a strong boil in the front pan but not as fast a boil in the rear pan. From what I have learned this is caused by too short a stack, not enough "flow". Do I need to make my stack even higher or do I need to take the cap off the stack? Could I just run my damper open more?
Unfortunaly I havent been able to upgrade the pans to drop/raised flue so I really need to make this setup work as well as I can.
thanks for the help
Tyler Rich

[ClarkFarmMapleSyrup]

I run a 2x3 half pint evaporator. I test boiled with new hood and stuff in the sap house so i could get a feel for how this would work for this season. we had a cap on it for the smoke sstack and for the steam stack. Took them off after 10 min. of smoke building up alot and not getting real good draft. The steam , we custom built a cap thats 1ft tall so there is enough room for it to escape and we put a fan in that steam stack.
But for the smoke stack i have no cap. If you dont want to have anything in it, just get one of the caps you pull on the string and it flips it up, then you can have it wide open when boiling. I fired the other day and wind was bad. But, i had such strong of a draft that i didnt need any forced air because that wind was drafting the stack so good.
just my thoughts,
J.C.

[vtwoody]

How close is the bottom of your back pan (that is not boiling well) to the bottom of the inside of arch? If you have too much space, a lot of the heat is escaping without getting up close to the pan. Not sure what the right height is for your setup, but for a drop flue, it is recomended to have the floor of the arch 2 inches from the bottom of the flues. I have a 2X4 as well and what I'm finding is that the short length of our archs does not give as much opportunity to capture the heat being generated in the firebox as well as some of the longer arches.

As to the height of your stack, if the fire is burning good and hot once you get it going(little to no smoke out chimney and fire burning briskly) than that is probably not the issue. If the fire isn't roaring, open up the damper on the bootm and add a blower - try a leaf blower or even a hair dryer just to see how much of a difference, if any, this will make for you.

Every rig is different but the tools avaiable for tweaking are consistent - lots of good ideas, of course, on this forum on various tweaks that have little to no expense.

Good luck!

[bubblinhutnh]

From the bottom of the pan to the tunnel where I have half bricks is about 4.5 inches. Maybe I should cut this distance in half and see if that helps? I can just use sand so I dont have to buy any more bricks......
I may also try it without the hood on the stove pipe, maybe that is restricting some draft......although with 12ft of stack on a 4ft arch I would think that is enough stack for it...
thanks for the help
Tyler

[fresh spout]

you definitely have enough stack, rule of thumb is that your stack should be double the lenght of your arch, so 8' should be plenty. 12' is more than you need.

[sbingham]

Tyler - My last unit was a 2x4', it sounds like you have plenty of stack at 12'
I would definitely tighten up the space between the pan and bricks in the rear of the pan, a space of 2" would be a good starting point to try.
After that if possible with your unit, I'd suggest a small blower to increase your evaporation rate.

[bubblinhutnh]

Ok I can just use sand to close up the tunnel right? I dont want to buy any more bricks for that purpose.
I will get some sand and close that up and take the cap off my stack and do a test boil, hopefully today, and let you guys know how it goes.
I'm not sure I can do a blower on my rig, but I will look into it.....
thanks
Tyler

[Fishgill]

You mentioned you had a damper. I would definitley leave it wide open. Or remove it all together.

[sbingham]

Tyler - I have been using vermiculite insulation instead of sand, light weight & easy to move around.
Last year I picked up a roll of 1/4" or 3/8" thick ceramic blanket to line the arch with before fitting the fire bricks. Had some extra left over and laid it over the top of the vermiculite to keep it in place, worked out great.
Most home improvement type stores will stock or can get a bag of vemiculite

[Stamford sugarmaker]

Tyler,

I bought a 2X4 from Randy like yours. I put a small blower on mine and it seemed to work very well during a test boil. I believe the 4.5 inch gap in your tunnel is too much. I have about 2 inches for mine. A cap at the top of my 8' stack was too restrictive so after removing it my stack temp went up to 900F. I leave the cap on when not boiling.

More tweaking probably will be necessary once I start boiling, but for now everything seems like it will work pretty good.

Peter