Combustion efficiency

[maple flats]

https://mapleresearch.org/wp-content.../combeffic.pdf
Use this link to guide you for AOF, (air over fire).

[Swingpure]

https://mapleresearch.org/wp-content.../combeffic.pdf
Use this link to guide you for AOF, (air over fire).

In paragraph 5a, they talk about a 15 to 25 minute wood charging cycle? What is that? Is that different than adding more wood every 6 or 7 minutes?

“ You will find that very little air will be required from the system, except at the end of the 15 to 25 minute wood charging cycle. Frequently, at the end of the cycle, it is advantageous to open the under fire air to a much higher level to burn down the charcoal that is built up, particularly if hard wood is being used as a fuel.”

[DrTimPerkins]

In paragraph 5a, they talk about a 15 to 25 minute wood charging cycle? What is that? Is that different than adding more wood every 6 or 7 minutes?

Yes, with properly designed and operated AOF systems you don't need to add wood as frequently.

[blissville maples]

I'd have to see it to believe it. Many things in this trade don't happen the same in the sugarhouse as they do for the makers of this equipment. It's kind of like that new truck that says you're going to get 24 miles to the gallon but you only get 18 very common with Maple sugaring just like an RO - show me an arrow that actually moves 600 gallons per membrane per hour. They don't but that's what they claim.

The only way I could see loading every 25 minutes is if you had some dry locusts or hickory about 8 in size!!

Best advice I can give anybody about boiling with wood just give yourself a stack thermometer and add wood according to that. 5 minutes 10 minutes 20 minutes I don't care about the minutes I care about keeping a step temperature around 850 to 900 regardless of timing.

I think these systems are Incorporated by LaPierre but if you look at their production rates per square foot of pan area they are not as high as say for instance a leader inferno which is what we run. We easily evaporate 5 to 6 gallons per square foot not too many other evaporators doing that and all we have is a blower up through the grates. A lot of technical jargon in all of that Aof read when it comes down to it all these manufacturers are trying to sell their latest and greatest just trying to make a sale sounding fancy in my opinion.

I was at the LaPierre open house they were running a two and a half by eight or maybe it was a 3x10 which is what we have and I asked the guy what the evaporation rate was he said something like 60 or so gallons an hour I don't remember the exact figure and I had to ask him is that syrup or sap because if it was syrup I would have been impressed but he goes no that's just sap and I thought wow I pretty much have the same size evaporator and I'm doing three times that lol instead of being a jerk I had to walk away before I did should have told him packed that thing up and get it off the lot because it doesn't evaporate half of what it should for the price!! And from the perspective of somebody that watched their neighbor boil on an evaporator that does high production they go get yapped at by one of these salesman buying evaporator that they think is going to keep up and at the end of the day it doesn't do what their neighbors rig that they saw does. Talk about a 30k dollar lesson!!

[Robert K]

Thanks Dave,
It been a few years and I forget to tell people about that research. I built my arch 2x12 around that along with help from some wonderful sugar makers on this site and a power generation engineer. If you are willing to take the time and build it right with the proper materials you can have a evaporator that boils very efficiently.

[eustis22]

This is pretty close so I will try here. This season I constructed a new shack but had to reconfigure my 2X3 Mason to exhaust out the wall and up the side of the shack using doublewall vs prior year's single wall out and up thru the roof. I am having issues maintaining a good burn and have to spend a lot of time turning the blower (AUF) on and off and keeping the door open at times. I got thru a small boil but it's not how I am used to doing and I'm wondering if my draft is now an issue.

The Mason exhausts from the back and the prior configuration was: six inch 90 degree elbow to 6-to-8 inch adapter to 9 feet of single wall 8 inch.

Now the config is 6-to-8 inch adapter to 24 inch 8 inch double wall thru side wall to tee and then 9 feet of double wall capped with 2 feet of single wall with chimney cap.

Do I have too much horizontal going to the stack?

[nymapleguy607]

Try removing the chimney cap, it might be causing a restriction.

[maple flats]

Any time you make the exhaust go horizontal, you are asking for problems. Why is it you went horizontal rather than vertical all of the way? Off hand I can't think of why that would be a good idea, maybe you can enlighten me.
What size is your wood split to and is it fully seasoned? What kind of wood are you using?
I once had a chunk of scotch pine with huge knots in it, the splitter I had (big box store basic splitter would not split it. I threw it in my firewood stack and said "I'll let the fire split it". When I threw it in the rapidly burning fire in the arch, it remained there for several hours. As I was cleaning up that night I noticed it was still unburned in spite of being in the inferno all day. I thought it was a fluke, and I foolishly put it back in the next day with the same results, I then threw it into the woods and someplace it's still out there. When this all happened I had high pressure AUF/AOF but that unsplit chunk of Scotch pine refused to burn. It was as if it was asbestos.
In all of my years since I never ran into any other piece of any kind of wood that refused to burn. I have heard that pines have a fire protectant in the bark, but why wouldn't the ends of the chunk burn in and just leave a hollow tube of bark? Sorry for the off topic rant!

[eustis22]

I went that way because I didn't want to deal with cutting a hole in the metal roof for the new stack. Didn't do a great job on my southern shack and I was pretty sure that my second attempt would be more butchery.

I am ignorant of pyrodynamics and had no idea if or how the config change would affect my burn. It didn't even occur to me to ask/google BEFORE I made this alteration.

my wood is wrist sized white pine that was cut down early last summer.

[eustis22]

Well the good news is if I open the ash door some I am able to maintain a good flame/boil rate without using the AUF. I did remove the rain cap and pull the extra grating from the firebox so crisis maybe averted for now. I will take relocation the stack under advisement but it would be a summer retrofit.