2x6 rate

[small_operator]

i have a Small Brother’s Lightning 2x 6 raised flue. i have vermiculite with insulation blanket on top even to rails, tapering 6” from back. i run dry hemlock some pine. i fire about every 10 minutes or when back pan starts lagging. i have a 15’ stack, no blower or steam hood. stack temp measures about 300 degrees, not sure of significance of that. only a little smoke to front when i first fire it. i seem to consistently boil 18 gph. this year is when i retinned my arch and raised insulation level. before, insulation level was about 2” below rails under back pan. i have 1” blanket all over with 1” brick in firebox and 2” brick on arch. i was really expecting to get over 20 gph. any suggestions? i thought about adding air over fire, but not sure how to do that with insulation so high in back. i guess i could put it just before insulation gets too high at the top of slope. i thought it would do better by raising the insulation level.

[BAP]

Easiest thing to do would be add air under fire. Either put a blower in your draft door location or cut a hole in the back of the ash chamber and put one in. Any squirrel cage blower would work and help. Also, fire a little more frequently, if you are noticing your boil slow down in your rear pan, then that means you should have added wood already.

[johnallin]

i have a Small Brother’s Lightning 2x 6 raised flue. ... i run dry hemlock some pine... i fire about every 10 minutes or when back pan starts lagging. i have a 15’ stack, no blower or steam hood. stack temp measures about 300 degrees, .... i seem to consistently boil 18 gph. .... i was really expecting to get over 20 gph. any suggestions?

- I'd suggest you fire more often and not allow the flue pan to start losing the boil...you're taking 2 steps forward and then 1 back...
- Hemlock and Pine are fast-burning woods and not real high in BTU's, Lots of heat but not for very long...again the need to fire more often.
- Stack temp seems low at 300, we run closer to 800-900 deg, but your stack gauge may be off.

I think the biggest culprit is your wood and firing technique.

[maple flats]

18 gph is far under what a 2x6 raised flue should get, regardless of the type of wood burned. First, what size do you split the wood? Then for fueling do you use a timer? Back when I had a wood fired2x6 evaporator, it was a drop flue, raised gets slightly more than drop flue. I fired every 7 minutes both on that 2x6 drop flue and on my next evaporator which was a 3x8 raised flue. Every seven minutes, before I added AUF/AOF, high pressure air under fire and air over fire. Once I had that I changed my fueling time to every 9 minutes. If your 2x6 has double doors, only fuel one side at a time and have the door open as brief a time as you can without tossing wood in and hitting the flues, fill the firebox up to about 2/3 of the distance from the grates to the pan. Close the door as soon as you can. You will notice that the boil slows or even stops when you open the door, so keep it a brief as you can. Split your wood to wrist size and make sure it's fully dry. Even just AUF will help, but both AUF and AOF are needed for best results. Keep the sap level at 1-1.25" deep, not more. If this list of points to follow doesn't get your evaporation rate up to more than 25 gph there is something wrong with what you are doing, my guess is it will be 30 gph +/- 2 gph. Make sure you give the arch all of the air it can take, open that draft, until you can add AOF/AUF and never have a damper in the stack on an evaporator for wood fired, if one is there, make sure it is full open. It takes lots of air to burn hot enough to get a boil burning real hard, the faster the fire the faster the evaporation rate.

[small_operator]

thanks for the info guys. i tried a timer every 8 minutes, and got a little better than 20 gph. i bet i just need more air flow. i used a laser pointer thermometer on the stack to get temp. sometimes it goes to 320 at peak burn. my stovepipe has a slight lean to it, and some leaks along the way, that probably cuts draft too. Also, i’ve been jamming the firebox too full from what Dave is saying. i’ll try with 2/3 full

[BigJon]

I used to get 60-65 gph boiling rate on my old 2x6 with good wood, filling the firebox about 10” under the pans. This was an airtight arch with AUF and raised flue back pan with a rear hood and preheater. Try to keep your stack temp at least 900 degrees. On my current evaporator, I average about 1200-1300 degrees using mostly pine slabs. Even if it’s a standard arch you should be at least around 25-30 gph.

[small_operator]

Anyone know a source for a squirrel cage blower. i saw some cheaper plastic ones online, but was afraid they might melt if close to arch. Maybe like an old furnace gun without the fuel pump?

[darkmachine]

On my home built 2x6 I'm using this blower. Got it off amazonDayton 1TDT6 PSC Blower, 2 Speed, 115V Works pretty good for us.

[maple flats]

On my 2x6 raised flue when I had added AOF/AUF (air under fire/air over fire) I hads stack temperatures with a temperature probe right in the stove pipe of 800-950 most of the time.
I suspect 2 main issues, but without actually seeing it i'm just guessing. 1. wood split too big or not fully dry
2. over filling the firebox, both can cause low evaporation rates. Even without a blower, if you give it enough air it should burn better.
Keep in mind, you need a real hot fire to boil fast, give it lots of air. If that doesn't help enough find a blower to push more air in, look for a blower that will move between 350-550 cfm (cubic feet per minute). If you find a bigger blower, use it, but you may need to use a slide gate to restrict eithen inlet or outlet air flow, if that's the case make it adjustable. Next, try criss-crossing the wood, a layer front to back, then one side to side and repeat until it's up to 2/3 full. Keep the door open as little time as you can without risking throwing wood in and denting the pan, especially the flues, but dents in eather pan is not good.

[maple flats]

You should get 25-30+ gph once you get the operation right. in fact 35 gph is possible.

[darkmachine]

I agree with Dave about technique too, I've noticed a huge difference in evaporation rate if someone else adds the wood and they aren't particular about how the wood goes in, evaporation rate can drop by 10 or 15 gph just like that. have to criss-cross that wood so that fire can breathe.

[maple flats]

It's about getting enough air to the fire.
One thing I noticed after I added high pressure AOF and AUF was that I no longer needed to criss cross the firewood. Apparently the abundance of high pressure air negated the need to criss cross the wood. If you search out the topic you will find it on the Proctor site, combustion efficiency.
You however need to learn the difference between a squirrel cage blower and a high pressure blower. Just because a squirrel cage blower moves lots of air, it is not high pressure air. The difference is huge. I like to describe it as a squirrel cage blower flings the air, while a high pressure blower throws it, The high pressure blower had paddles that each throw the air at the blower outlet. It's not the volumn of the air but the pressure of it. While I lucked out getting a HP blower free, most need to pay big bucks for one. My free one came from a closed down factory, it was mounted up high in the rafters and a friend discovered it was still there several months after the factory had been closed down and cleaned out. It was actually used to create vacuum for presses punching doilies out of paper. It was 3 phase and had to get a new motor, and mount, but in the end it worked perfectly as a high pressure blower and one I could afford. If I recall it cost me 1 qt of syrup, maybe it was 2.
Anyways, back on topic, this could solve your efficiency issue and more than doble your gph. While my efficiency was quite good before, with the HP blower AOF/AUF it rose about 20% more after while burning about 1/4 less wood, a win win in my book. Take note that I ran HP air to both under the fire and over the fire, not just over it like the report about combustion efficiency describes. I suspect my gain would not have been as good and likely I would have needed to criss ross the wood too. For me to get the HP air to both, the blower was coupled to a 4" pvc pipe, outside, under my head tank. From there it went inside the sugarhouse using 3 long sweep ells to end up on the floor facing the arch. I had a trench for it. As that 4" pvc pipe got under the arch, I split it using a 4x3x3 wye. One 3" went in under the back of the arch in a 4" heavy gauge galv. steel pipe, the pipe was on the floor and was ended and capped at 6" short of the front of the arch. In the pipe I had 3 rows of 5/16 holes, one row top center spaced about every 3", and one on each side facing theouter edge of the grates spaced the same. Each 3" pipe had a ball valve in it to regulate the portion of air to each. The other 3" went up into the slope of the ramp behind the firebox in the arch in a 2x2 square tube, which split into 2, one going to the rt and one to the left side of the fire and each had a 1/4" b;ack pipe nozzle, facing downward about 12-15 degrees and facing the opposite side grate. The nozzles went completely arond the fire except over the doors. I'm going from memory, but I think I had the AUF valve open about 1/3 and the AOF valve open about 3/4. For better details look at my original post from way back when I had first built the system. In the beginning I experimented with various valve settings, but in a very short time I found what worked best and never adjusted them again. My big question in the beginning was if the 2x2 tube I used would be large enough, Since I never tried using larger I'll never know, but the results were fantastic so I never changed them. Where the AUF transitioned from 3" pvc to 4" steel pipe (like smole pipe) I cut slits and pushed it over the 3" pvc and clamped it using a hose clamp and sealed it with duct tape. The 3" to 2x2 square I used a Fernco connector sized to do the job, I woyld guess it was 3.5" x 3 maybe, and hose clamped it together. Bothe connections were under the arch, not in the heat of the fire.

[SeanD]

Hey Dave,

I just tried to send you a PM, but your box is full. Popular guy!

Sean

[maple flats]

Thanks for the heads up, I cleaned it out. I should request from Peter Gregg that as a moderator, I should get more space in my inbox, I do get lots of activity. However, I must admit, some of the messages I cleared out were not really current. Maybe I just need to watch it closer.\

Dave

[SeanD]

Ok, great. Just sent it. Sorry if you get more than one. I was getting an error on my side before it finally went through.

[small_operator]

thanks Darkmachine, i’ll check that out.

[Super Sapper]

It sounds like you are not getting enough air. Even without AUF you should be able to do 30 plus. A few things that come to mind are having a large enough draft door under the grates to let enough air in, make sure that you fully cover the grates with wood. If not fully covered the air will short circuit around the wood. Do not let too many coals build up as that will choke off the air also. Stack should be at least 8 inches without any damper in it to restrict air flow. With my home built 2 x 6 drop flue, I could get close to 40 gph without AUF and up to 50 plus with a blower. Do not fill your firebox full, fill it 1/2 to 3/4 at the most. How much will depend on the air coming in and the wood you use. When using a blower, you can fill it fuller as you have more air for combustion.

[220 maple]

If you add steam to your 2x6, you can get 25 to 30 gallons of syrup off an hour as long as you sweeten it to 22 brix. That I guess is a good boiling rate, source Clayton at MES!
Mark220maple

[amasonry]

I know on my evaporator burning hemlock and or pine I lose 10 gallons an hour off the boil rate. just from having to open the door so much. loading every 3-4 minutes

[Gord]

Anyone know a source for a squirrel cage blower. i saw some cheaper plastic ones online, but was afraid they might melt if close to arch. Maybe like an old furnace gun without the fuel pump?

I have bought from surplus center many times. They have a pretty good selection of fans and blowers. I have a simple blower on my evaporator with a varying speed switch on it.

https://www.surpluscenter.com/Electrical/Blowers-Fans/