A different blower question

[Uncle Tucker]

My 2x6 is new his year and I put a blower on it. The thing I noticed is after about 5 or 6 hours of boiling the boil in the flue pan slows, and only boils about half the length. The stack gets bright red about 5’. There is black smoke shooting out the stack. I thought that the blower was pushing the fire up the stack but the front pan was rolling right along. I tried shutting the blower off and opening the draft door to see what would happen. The red spot on the stack shrunk to about 1’ and the flue pan boiled the whole length, the front pan slowed right down and the front corners stopped boiling. The stack was still shooting black smoke out.
The thing I don’t under stand is if the stack is so hot, why won’t the flue pan boil the entire length? And why is the smoke black? I know it is unburned gasses but I though it would get enough air with the blower.
The other thing I was wondering is, how much heat is going up the stack to make a stainless stack glow BRIGHT red for 5’? Too much???


I am considering drilling a ¾” hole in the ramp and attaching a 3” flexible duct from the blower to a piece of 3/4” pipe and sticking it in the hole to get some air in the back of the fire and in the flues. I talked with Glen Goodrich and he though it would work.
Any thoughts??

[ibby458]

I have no idea what might be causing those things, but my first thought was cresote/soot buildup on the bottom of the flues. Is your wood dry? Have you brushed them? It almost sounds like you have a chimney fire in there with forced draft, but when you slow down the hot gases by shutting off the blower, the heat seeps thru the soot and makes it boil better.

How much room is there under the flues? It shouldn't be much. I could see where a forced draft would blow the heat under the flues instead of between them.

[Brent]

I hate to suggest it when you've got a brand new rig, but have you looked for a leak. Raging fire, black smoke and low boil. Strange.

I hope it's anything but.

[hookhill]

Glad you posted this problem because that is exactly what we expierenced. When we added a blower the front pan evap increased and the back pan evap decreased. The black smoke on ours disappears after 4 hours of boiling due to the whole rig getting up to temp. We talked with Glen about it as well and he suggested adding air further back into the arch. Let us know how it works for you.

Jim

[sweetwoodmaple]

Yup, have the same issues too. Just added a blower to my 3 x 10 this year.

I have been fooling around with the air flow, and have noticed that it's a "rob Peter to pay Paul" situation.

If I increase the air flow (make it a blowtorch type fire), I get a lot of radiant heat in the front and it makes the front pans and the front of the flue pan boil like crazy. The problem is...you have to add wood every few minutes. Also, I think the air rips by the flues too quickly and doesn't have time to absorb the heat.

I think it all has to do with flame contact vs. airflow. You have to balance the two somehow. Just putting more air on the fire doesn't do it. (though it does help when you have wet wood like me)

[mapleack]

Brian, how many gph are you getting with your 3x10? Do you have a stack thermometer on it? and how many feet, what size stack? I too have a 3x10 with a homemade blower. I'm currently running 90 to 100gph with it and surface stack temps of 580 to 620. Thats with 30' of 12" stack. I only had 18' on at the start of the season, the extra 12' added 140+deg stack temp and 15gph or more. With medium size dry wood I fire every 6 minutes. With small pieces of really dry wood its more like every 4 minutes.

-Andy

[Uncle Tucker]

I think I found some of my problems. I let my friends fire the evaporator for a few turns and they were thronging arm fulls of wood in. they said it lasted longer that way. After some debate, we decided to use less wood. I think that the wood made a lot of creosote and made a chimney fire.
I boiled the other night and I tried firing a couple different ways. The best way I found (so far) is a couple of pieces of wood every 3 minutes, and keeping the fire so, I can see the grates still after I add wood. It keeps a hotter fire that way and I don’t go through as much wood. The smoke is still pitch black, I am trying to fix that still (a little embarrassing, people must think I am burning plastic).
I know that there are unburned gasses so I think there isn’t enough air in the firebox. I am going to try cracking the door next time I boil. If this makes the smoke go away, I know it is starved of air.
I think I am going to add the pipe to the ramp and blow air in there to get the gasses to burn. If it doesn’t work, back to the drawing board.

[maple flats]

I have not yet added a blower and won't til I finish my concrete floor. Right now I have cancrete under the evap and from there to one wall, but the other side is still wood and I fear blowing sparks on the wood floor. However I have no smoke at all after the first few minutes on start up. After that I have the draft door open half way (about 18" x 6" opening with door flap up at 45 degrees) and there is zero smoke. I do not know if adding a blower will change that. From my wood boiler days I can say that smoke comes from incomplete combustion but I can not say what you need to do to correct it.

[Brent]

A guy around here with grey hairs and lots of syrup experience says one of the most important investments in a sugar shack is an egg timer.

Set it for 6 minutes, when it goes off, re-set it first, then add wood, scoop foam, a 1 to 4 drops of defoamer and sit down. Repeat as long as the sap lasts.

He was especially emphatic about the defoaming. He was insistant that most vapor is lost off the surface, not from the actual boil, and that foam really slowed down the surface vaporization.

For what it's worth.

[tappin&sappin]

I agree 100% w/ the thought of adding less wood more often vs more wood less often. With loading up the firebox, you block the heat from the pan, and it takes a while for all those chunks of wood to catch fire.

What kind of wood are you burning? I found if I burn cherry or oak the boil isn't near as good as it is w/ tulip poplar. I love burning that tulip poplar. Make sure too when you load it that you "stack" the wood in the firebox so that air can get to all the pieces of the wood.

As for the foam... I always try to knock down the bubbles as soon as I see them coming on. But, someone told me that the bubbles actually create more surface area and thus will evaporate more. I still put a drop of defoamer in when I see things starting to foam up.

I've got a 2x6 and when things are running good, I think it does a little better than 20gph, but when all said and done, the average is always 20gph.

I just added some fire brick in front of the flues (very bottom) to try and force the heat through the flues. I haven't tried boiling w/ it like this yet, but am hoping it helps.

Good luck.

- Jake

[Uncle Tucker]

I fixed my smoke problem!!! The blower was under sized. I bought a leaf blower for $25 at Home Depot. I also put ¾ “ pipes in the back ramp of the fire box and used the other blower for those. Works great, no black smoke at all. The back pan is throwing sap ever where, it’s jumping out of the pan, I mean jumping! Next year I will replace all the blowers and get the right size for my stove.
What size should I get for a tight single door 2x6?

[RileySugarbush]

I'm using a 200cfm, 115 volt shaded pole motor from Grainger item 4C754

Works great and not too loud

[sweetwoodmaple]

3 cfm's per square inch of stack area.

If you have an 8" or 10" stack, 200 cfm should be enough.