Too MUCH draft?

[ibby458]

When I set up this evaporator, I put in a small forced draft unit, and it was the most useless thing I did. Within minutes of sstarting the fire, the stack temp was over 700 degrees, and the sap was jumping so high in the flue pan that it was hitting the slopped sides of the hood and running back into the condensate channel. Even with the draft door shut and propped tightly closed, it still was out of control. (I also closed the intake on the forced draft unit.)

I had built a heavy duty stack cover, and shut it to calm the fire down, but the force of the smoke kept it 3-4" open. After a bit, it slowed down to a good strong boil, and I left it that way for the rest of the day.

This rig came with 14' of 14" diameter stack, so that's what I used. It's all stainless, so I don't want to replace it with something smaller.

I'm thinking maybe if I raise the bricks under the raised flue until they almost touch, that might slow it down and increase heat absorbtion. (They're 2" under the bottom of the flues now.

Any comments or ideas?

[mountainvan]

I usually have my stack temp at 800 and get a good strong boil. If the blower does'nt have a reostat on it to control the speed/cfm I would start with that. I have a dimmer switch on three blowers hooked together. I have 1/2 power with dry wood, but full with wtter wood to get good combustion.

[maple maniac65]

My stack temp runs 1200-1400 normally. I fire every 12minutes with good dry hard wood. I have ceramic blanket under a drop flue so the heat has to go through the chambers. Sap temp in preheater runs about 190. Depending on sugar content in sap I can make 3-5 gallons an hour of syrup. The only time that I made 5gph was after a cold snap and there was a foot of ice in my tank with 400 gallons of sap. Sugar content to start with was 2.8 and ended up at 6.2

I have 26' of 10" ss stack. My boil rate on a 30x8 revoulutiondrop flue is 115gph. I make about 35 gallons of syrup per cord of wood.

The hotter it is the faster I boil. Just watch pan temps in all compartments. Defoam at regular intervals. Syrup should bubble up front but not foam.

I visited a sugarhouse last week with a 2x6 oil fired and the back pan was 10" high with foam and the front pan was boiling over all 4 compartments. They could not figure out why that they could not consistently make syrup.

[WF MASON]

People pay alot of money to get their evaporators to work like yours, sorry but I couldn't find a problem.

[maplwrks]

Sounds to me like you may have too much sap in your flue pan. Make sure your rig is level and sap is about 1" over flues. I don't think that you can make an evaporator boil too hard!

[maplehound]

Brad Gillian Told those at the Ohio Maple Days this year that you r evaporatore should sound like a freight train. The more noise they make and the more the sap jump in the flue pan the better. If it is jumping out of the flue pan then lower the level in the flue pan. 1" is all you need over the flues.

[WESTVIRGINIAMAPLER]

Maple maniac,

What are you doing to get 115 gph out of a 30 x8?? Are you using a steamaway or piggyback or just an inferno arch and preheater??????

[ibby458]

Thanks for all the advice! I described it more like a jet engine taking off, but it sure is noisy.

My sap level in the flue pan is about 2" as I get used to this rig, but I will lower it and see how it goes. I use a drop of commercial defoamer whenever I see foam, so that's not an issue. What's happening is boiling sap is jumping 10-12 inches out of the pan. The previous owner told me this would happen, and included some shields he had fabricated to keep the jumping sap in the pan. I put those in, and they helped.

I FULLY believe 115 gph, at least in spurts. The boys filled the firebox solely with dry spruce & tamarack slabs once, and I watched the feed tank drop 10 gallons in 5 minutes. Of course, that firing only lasted the 5 minutes! Mixed slabs and dry, split hardwood seems to be the best compromise.

I guess I don't have a problem so much as a situation that I need to learn to adapt to. Sure is a far cry from working like crazy to keep the back pan boiling full length like I did on the rig I used last year.

I don't think I'm going to make any structual changes this year, but I will raise the deck under the flue pan for next year. That should make it absorb more heat, and slow down that draft just a bit.

[tapper]

Ibby,

The 14" dia. stack sounds like a bit much for a 2 1/2 x 8. maybe if you just take 2 ' off the top that might help some too?

[ibby458]

My sugarhouse roof is flammable (not metal), and I'd rather not lower the stack. I had thought of adding a 14 to 12 reducer and 2' of 12 " pipe, but that would be a bit costly, and may not help much.

[Fred Henderson]

You could just use a piece of galv for a trial, that would not cost to much.

[John Burton]

I like the idea of lower sap depth in the flue pan i typically run 1.5 over flues . any more than that and you get the condition you are talking about.like bill said alot of time and money have been spent to get where you are. as long as the front boils as good as the back i would say your looking great.

[ibby458]

Actually, the front pan wasn't boiling well until I lowered the stack cover. That helped a lot, but the outside channels still aren't boiling as well. With only the one test boil, I wasn't able to experiment with different firing techniques, etc, but I should get a good gather today and try some different things.

Thanks for all the advice!

[John Burton]

i run a beckett oil burner blower for my forced draft unit I haw to choke the intake port with a wooden shingle or i can drive the heat too fast up the stack

[Russell Lampron]

Ibby,

It sounds like you like your new evaporator better than the 2x9 you cobbed together to boil with last year. Are you glad the old farmer decided not to sell it?

Russ

[Fred Henderson]

If any of you guys seen where he lived you know why he has too much draft. On a calm day you still have to hold on to your hat. One good thing is and that is he will never have to take out the ashes because they are all up the stack.

[ibby458]

You got that right, Russ! This is Soooo much better!

You're right too, Fred. After boiling for 5 hours the other day, I don't have a spoonful of ashes in the pan!

Picked up a big load of sap yesterday. Heading out at 4:30 am to start boiling!

[Fred Henderson]

I picked up 300 plus gals and bioled last night. No vapor locking I had the sap jumpin right out ot the flue pan. I need more draft but I like having the SH in the woods.

[ibby458]

We made 22 gallons of medium Amber in 10 hours yesterday. It boiled at a pretty constant 65 gph, but I could push it to 80 gph if I fired virtually non-stop with pine slabs. Way too much work, so I settled for the 65 and firing every 8 minutes or so.

It probably would have been 23 gallons, but there's over an inch of burnt sugar on the side of the flue pan and arch (And plenty of dribbles of syrup on the floor) from the sap jumping out of the pan and running down the outside. I'm heading for the store as soon as they open to get some aluminum flashing to build some really effective baffles to stop that from happening again.

Picked up 280 gallons of sap yesterday. It'll be a good test of the new baffles.

I put a chain on the stack cover control wire, letting the extra weight make it a sort of barometric damper. Stack temps still in the 800 range, but it seems to hold a bit of extra heat in. Shiney Stainless stack is all gold & purple now. :(

Still - it works great, and I'm pleased with it!

[ibby458]

THe sap shields/baffles I made worked great. No burnt sugar on the sides of the pan or arch. All the sap stayed where it was supposed to.

I also lowered the flue pan level to 1", and the syrup pan level to 3/4" Works great, but little margain for error. Almost had an incident when I paid more attention to a visitor than the pan.

Interesting thing is the boil rate. From a pretty consistent 65 gph the other day, yesterday it had dropped to 58 gph, even with the lower levels. I suspect some of it was due to the fact that concentrated sap was no longer jumping out of the pan, and I think I may be getting some short circuiting due to the way the float and float box is constructed. (I switched draw off sides for yesterday). I'm switching back today, so we'll see what we see.

[Fred Henderson]

I don't care what mine is doing. I know that it is faster than my old one.

[archangel_cpj]

what is your fan and how is the draft ducted to the unit???

[ibby458]

I'm not using the blower at all. The natural draft is almost too much. What I put in at first was a huge oil burner assembly, with all the burner parts removed, leaving just the 8" squirrel cage. I ducted it to the arch with 4" round duct. I never meant for it to be a full forced draft, just a draft booster.

[Dave Y]

ibby,
sounds like you got that rig all most figured out. to make syrup I have found that you are only 30seconds from a catastrophe. Thats why it is nice if some one is there when you are boiling. I boil by myself alot, and I don't have time to even go to the restroom. Good luck wiyh that new rig.

[archangel_cpj]

Im thinking of getting one of those floor drying fans (squirel cage and ducting it right in what ya all think OH Ive got a 2x6

[SteveD]

archangle...here is a post from a thread on this same topic last year...complete with a URL for the purchase of the fan...


http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?xi=xi&ItemId=1611630891&ccitem=

4C447 is the dayton blower I put on my 2 x 6. Best bang for the buck ($70) and ran my evaporator very well at almost full speed. I arrived at about 3 cfm per square inch of stack area is a good rule of thumb. (Brandon- I believe this is the one that is on your wood saver too).

I went through several iterations with my blower. The thing you have to be careful with is the amount of pressure (expressed in inches of water) that the fan can generate. The ones with low HP vs. flow rate usually cannot generate much pressure. You need a few tenths of water pressure to adequately push air through the ash pit.

Good luck.

-Steve

[tapper]

I had a squirrel cage blower out of the junk yard on the 2x6 that I used to have. Used it that way for 10 years it made a big difference. I had a rheostat on it to control the speed.

[archangel_cpj]

crap its been discontinued will have to pull out the grainger catolog

[RileySugarbush]

I used a 4C754 from Grainger which had more power and was bigger diameter and slower speed, so I think it is quieter. It has plenty of capacity on my 2x6, and has good performance with some load on it. Get a fan that draws at least 1.5 full load amps and up to 2.0 and you should be OK for an evaporator of about that size or slightly larger.

[WESTVIRGINIAMAPLER]

Plenty of Dayton blowers on ebay if you are patient, especially the 4c447 which is a 265 cfm blower. About everything that is discontinued thru Grainger online is available in local stores.

[Sugarmaker]

Ibby,
I think you are just in the early stages of getting used to a rig that can really boil. I have to keep a little defomer in the back pan to keep it from boiling over. The front pan is a constant rolling boil in all compartments and have dialed our blower (550 CFM) back to low speed because the stack gets too hot! Boil hard as the rig can go!. Yea some one mentioned that when making syrup you are only 30 seconds from disaster. That is right on the mark! Boiling slower than that you are just coasting and not utilizing the equipment to its fullest. I have seen some folks boil in slow motion and wonder why the syrup is dark. Making syrup and controlling and roaring fire are not for the faint of heart!

Regards,
Sugarmaker

[WF MASON]

"Making syrup and controlling a roaring fire are not for the faint of heart"...you certinly have a way with words Chris. I've never quite looked at it like that. But running on the 'edge' of 3/4"of an inch in both pans, knowing what might happen , and not being able to stop yourself from adjusting that float just a little lower, the thrill of having the drawoff valve cracked open with syrup running out nonstop as you boil, for 'thoes' people , there can't be 'to much draft'.
I've never heard of someone giving up sugaring becouse its to stressful, but in todays world , I suppose its possible. I'll pass on the rollercoaster thanks.

[ibby458]

I guess I was unsure of the rig just because it was such a change over what I used last year. That one, I had to crank a blower so hard it was blowing ash all over the place, just to keep a boil. Not a problem now!

I'm still not happy about all the wasted heat up the stack, and the amount of wood I'm using, but I'm making good syrup, and making it fast, So I got no gripe!

[ibby458]

Too much draft wasn't a problem yesterday! The wind had shifted to out of the east, and I had a hard time getting it to boil good. The only reason I could see was the wind was hitting the open stack cover and causing a bit of a down draft. By firing mostly with dry softwood slabs, I was able to mostly keep up the evaporation rate, but it was a LOT more work!

It's a juggling act, for sure - and every day's a new adventure!