Stack temp./blower question

[Bucket Head]

Hi Guy's,

A while back I asked what everybody was getting for stack temps. on their 2x6 rig's. The range was from 800 to 1200 and a 2x8 owner responded with a 1650 reading on his.

Well, I guess I need more air!

I have had a maximum reading with a digital probe type therm. of 730 degree's. I backed it down from that to around 550 because at 700, the syrup looked like it was about to jump right out the pan!

I take it that everybody has this going on in their front pan with stack temp's that high?

Does everyone know how many cfm's their blower is putting out? How big of blower is reccomended for a 2x6?

Does everyone have hot ember's/ashes coming out of their pipe with that much air ? I do not have any ember's coming out of mine, so I figured that was good.

I'm trying to get more of my flue pan to boil, but is there such a thing as too hot? I was'nt planning on needing someone to stand gaurd with the garden hose while I boiled, LOL.

Steve

[brookledge]

With my inferno arch there is no ash pit so the blower blows it up and out. That causes hot embers to fly out so when you are turning up your blower expect to see embers coming out.
As far as too hot. The only thing that can happen is you are wasting fuel. You can compare it to your car. put the throttle down and you will go faster but will also use more fuel. The same goes for your evap. Crank up the wood and blower you use more wood but save time vs a lower stack temp and use less wood but a slower boil.
You need to find a happy median for your own set up
As for the flue pan yes the sap should be jumping
Keith

[tapper]

Steve,

If you can make sap jump with 700 degree stack temps you are doing good. I dont think I would change anything if you are happy with the boil rate.
I average 1200 stack temps and at times have been up to 1600 on my 2 1/2 x 8 with 980 cfm fan but, feel a lot of energy is going up the stack and would opt for the 700 degrees any day. After 2 seasons I havnt had to clean the ash pit because it all blows out the stack. One cool calm evening there were hot embers 50' above the top of the stack. It's a good thnig the woods were wet the entire season.

[Brent]

I think the above 2 posts are starting to get this whole discussion about stack temps back to a much more rational level.

1600 degrees in the stack is a HUGE amount of heat the does you absolutely no good. But 1600 degrees in the fire box and 1000 in the stack means you've put lots of the heat to good use.

If you want to make your fire that hot you should have longer pans to take more heat out of air flow before it goes up the stack.

But if you've got lots of wood and you're in a hurry, and like a big impressive number, then go to it.

Rather than blow more air in under the grates, this summer I'm going to play with injecting air through a small manifold somewhere near the beginning of the flue pan to burn more of what would otherwise just go up the stack, hopefully getting more heat out of the same load of wood.
Should be interesting to read the temps and note the boil, then turn the injector on and off, then move the manifold forward and backward under the flues. I expect it will be pretty graphic if it works.

I'd love some input from anyone that has done this before

[WESTVIRGINIAMAPLER]

You have to do what works best for you, whether it is 500 or 1500 stack temps. Don't worry about what stack temp someone else has. I burn all hardwoods and mainly locust which is the highest btu wood available and my wood is seasoned usually for at least 2 or 3 years and been in the dry from 8 to 12 months with air circulation helping dry it before the season starts, thus one of the reasons I can run 1650 stack temps. Just because it works best for me don't mean it will for you.

[Sugarmaker]

Good comments on stack temps. This was my first year to even monitor them and the 700-750 deg range seemed to be a avg boiling temp using a magnetic thermometer on the side of the stack. (had to screw it on)
As far as blower CFM we have a 550 cfm Dayton which also has 2 speeds and a damper control also. I can notice a difference if I have to much blower cfm's. When I back off a little more heat is in the fire box and the syrup pan temp goes up. But at the same time I also lose a little bit of boil in the flue pan, so I just try to fire consistently and keep the stack around 700 degrees.
Like Brandon says "works for me":)

Chris

[Brent]

Chris

this trade off between the slower blower into the firebox raising the flue boil and actually running a bit cooler in the syrup pan is why I am wanting to play with the idea if injecting fresh air somewhere under or just at the front of the flue pan.

Modern woodstoves are trending away from catalytic burners to re or post burning with air injectors and turbulence.

I think a very small blower under the syrup pan would be helpful, but I think there is a lot of unburned stuff in the plasma under the flue pan and I think if you could inject air there, you would get a better flue pan boil with greater wood / fuel efficiency.

[RileySugarbush]

I have a 200 CFM blower on my 2x6 and get about 35gph or better with stack temps between 700 and 800 magnetic thermometer. I've been thinking about routing some of the air to the top of the firebox. But I think it is important to have some significant air coming up through the grate to get complete combustion and keep the grate cool.

[WESTVIRGINIAMAPLER]

If you are running 800 stack temps with a magnetic outside thermometer, it would correlate to aproximately 1200 degrees with a stack thermometer with a probe like I use. I think you add aprox 50% to the reading of the outside magnetic thermometer.

[RileySugarbush]

Brandon, I think I will get a probe thermometer for next year. Didn't you have a recommendation for one? Could you repeat it?

[WESTVIRGINIAMAPLER]

Here goes:

http://www.condar.com/meters.html



3-39 FlueGard™ Thermometer
Best probe thermometer for fluepipes. Durable genuine porcelain enamel with yellow and orange zones clearly indicated on brown case -- shows temperatures in the center of the fluepipe, at a glance. Stem length 4 inches, engineered to measure accurately, for any diameter fluepipe up to 8 inches. Requires ¼ inch hole. Mounts easily with included magnet and eyelet. Readings up to 1700° Fahrenheit. Rugged steel case. Made in USA

FlueGard 3-39 Probe Thermometer
Shipping Weight 1 .lb $23.35

[OGDENS SUGAR BUSH]

And Get This Its Made In The U. S. A.

Rich

[Uncle Tucker]

I have been playing with air injection this past year. I don’t know if you remember the problem I had with black smoke, well one of the things I did was add air up top. I didn’t want to run pipes in the firebox (probably melt) so I drilled holes at the top of the ramp. I went to Lowes and got ¾ x6” pipe stubs and a ¾ x2” reducer put them in the holes and added the old blower to them. Then I bough a used leaf blower and put some real air under the fire. It worked awesome! I had a great boil in all of the front pan and the back pan was boiling so hard sap was splashing all over the place. The flues boiled from front to back and even in the back corners. I just got a 273 cfm blower and I will replace all the other stuff that is thrown together with the new blower and some duct work. I was tolled to put ¾ of the air above the fire, with the dampers I will adjust the mixture to see what works best. Stay tuned for further results.

[Sugarmaker]

Brandon,
Thanks for the link I have the first one listed and there may be a big difference in the probe style verses the outside reading.

Unkel T,
Sounds like you had good results directing air to a specific place in the fire box. Keep us informed.

Chris

[Justin Turco]

www.condar.com Check out the 3-39 for 23.35 or the 3-19 for 22.50. We use the 3-39. works great. Brandon told us about it.

Whoops. Didn't see that the info was already posted on page 2...sorry.

[WESTVIRGINIAMAPLER]

Jon(tapper) is the one who put me onto it, so he gets the original credit. I bought mine from a local stove dealer, about the same price and didn't have to pay shipping.

[Uncle Tucker]

I think the above 2 posts are starting to get this whole discussion about stack temps back to a much more rational level.

1600 degrees in the stack is a HUGE amount of heat the does you absolutely no good. But 1600 degrees in the fire box and 1000 in the stack means you've put lots of the heat to good use.

If you want to make your fire that hot you should have longer pans to take more heat out of air flow before it goes up the stack.

But if you've got lots of wood and you're in a hurry, and like a big impressive number, then go to it.

Rather than blow more air in under the grates, this summer I'm going to play with injecting air through a small manifold somewhere near the beginning of the flue pan to burn more of what would otherwise just go up the stack,
hopefully getting more heat out of the same load of wood.
Should be interesting to read the temps and note the boil, then turn the injector on and off, then move the manifold forward and backward under the flues. I expect it will be pretty graphic if it works.

I'd love some input from anyone that has done this before



Bret I did this at in the middle of last season with great results. This summer I added a new 275 cfm blower and remounted the injector blower and new rope gasket around the door. Last year the flue pan would boil so hard, sap would jump high enough to hit me in the face. This year I will have a steam hood to keep all the little black dots off the stack base and the red dots off my face. I have rearranged my pictures and added some of the air injection pipes and blowers.

[Brent]

I suppose the great thing about adding this kind of injector, above the fire or near the beginning of the flues, is that it would be easy to turn on and off and watch the stack temp and boiling respond. The stack temp should respond in a few seconds.

This takes out the variable of fuel/firing. If the temp goes up, it's pretty well got to be the air injection, and you've got the heat free, because it is not consuming more wood !!!!

Got to get busy and test it. Happy 4th of July to all you southern folks