New 3x10 homegrown arch F A LAZY

[windyacres]

:(Front half arch boils 100% . Only 2 feet boiling pan working. 10 inch stack (oil conversion ) 800 cfm -8 WC .Over air 15 3/8 nozzles dual feed thru 2 inch stainless header. Under air 15 3/8 ho les in 60 inchs of 1.5 header under fire :(. Suggestions ?

[mapleack]

Do you have dampers to control how much over fire and under fire air you're getting? Do you have castiron grates or do your under fire nozzles come through brick? If they come through brick you need a lot more of them. 12 holes per square foot of chamber floor is recommended. How long did you boil when you made your observations? How often did you fire, how full was the fire box, etc? Did you boil long enough to guess at your evaporation rate? More details will help.

[nymapleguy607]

Okay so it sounds like you have a 5ft fire box? Im guessing the flue pan is around 7ft, sounds like you have a draft problem either your lacking enough draft to pull the fire and flames back under the rest of the flue pan or your running the blower to hard and shoving heat up your stack. What are you running for stack temps?

[windyacres]

Stack temp very low -300 ?? should be closer to 1000. My stove therm wouldn,t stick to stainless. funny thing is that cutting air back can actually be as good as more air depending where in the load cycle air is cut back . 4 foot firebox then one inch clearance till about 9 inches from back exhaust (not vertical exhaust)

[windyacres]

Andy ; Have 3 dampers ,2 for over air-one each side,one under air .Over nozzles 5 each side and 5 across back of firebox-6 inchs below the start of 7 foot flue pan. under air isof firebox fed by i.5 inch stainless manifold 40 inchs -15 3/8 holes - 3 runs at 16 inch . 400 sq inch base of firebox .i am going to change to 3/8 nozzles before next boil in base . Air is cover by grates leaving small cavity at base of fire. no wood first 3 inches of box and an insulated airtight door. 40 gph for 1.5 hours- mediocre wood no hood preheat.

[mapleack]

It can take an hour for the fire bricks to totally heat up and reach peak evap rate, but 40 is way way too low. For one thing I don't think you're getting enough air under fire, you need twice as many nozzles in your under air. I was wondering if all your heat was going up the stack, but if it's 300 then that isn't the problem. Do you have a barometric damper installed? Long term you'd be well served to get a stack therm with a probe into the stack to be able to monitor as you boil. I think you have a big enough blower so the lousy wood shouldnt matter as much. How much wood at a time and how often? If you haven't read the publication in this link, do so. http://www.uvm.edu/~pmrc/Combustion.pdf

[windyacres]

i used the proctor research on combustion as a blueprint, but deviated ]in that i did not initially use nozzles . i will be adding twice as many nozzles under air and a better grate system to put a thin layer of air under fire. have not got a real run of sap yet. i have fired on a 12-20 minute interval . Thanks for all the good advice. i will report progress.

[nymapleguy607]

I would agree you need more air ubder the fire. If your only at 300 in the stack the upper air is not really doing anything but cooling your pans. Gasification takes place at temps around 1800 degrees in the firebox. You will need to play with your air settings but generally seasoned wood you'll want your overfire air on fully and the grate air shut off, if its bone dry wood you can cut back on the overfire air a bit grate air will still need to be shut off, and if its green wood then overfire air on full and you'll need to play with the underfire to hold a certain temp. Definitley get a probe type stack thermometer this will help you see how your adjustments effect the temp.