AUF over heating stack?

[Hunt4sap]

My 55 gallon barrel evaporator that I made 2 years ago has a 6in single wall black stove pipe flu that is 14 foot long to get out through my roof I am averaging about 4 to 5 gallons per hour boil rate. ( I am using a turkey fryer and stainless steel flat pan for a preheater)

I read a lot about air Under Fire with a small electric blower motor and I could easily add this to the front of my stove as I have to in fire rated insulation rapping around the side walls and bottom and fire brick on the side walls and bottom and I just use a old fireplace grate to keep the fire up to let air naturally flow Under Fire while boiling now.

I don't have a temperature probe in my stack but I am going to put one in, but I'm wondering what the best height from the ground or the best height from where stove pipe exits back of barrel up to temperature sensor needs to be and what is the highest temperature that this black stove pipe can handle only being single wall?
I have wood Walls Within 1 foot of that single wall pipe and it gets very hot already from the stove pipe being so close.

I guess other than the question about the temperature probe placement my second question would be with everything that I have told about my exact setup would a blower fan get my stove pipe stack too hot width an air Under Fire blower?

Thirdly when guys run these is it normal to have a damper where stove pipe exits stove (I have one in my stove pipe currently that I used to regulate my boil and if my flue pipe gets too hot I can close it some to cool my stove pipe down...)

Width how close my stove pipe is to my wood walls I believe if I did put air Under Fire I would have to insulate either the stove pipe or the wall because in my mind if I'm blowing air into that fire it's going to make it boil faster which is great but dealing with the excessive heat that's going to be going up my stove pipe might be a problem?

Sorry for being so long-winded but I like to give as much detail as possible when asking questions...
Thanks Matt

[Cjadamec]

You should have a heat shield on the wood walls as it is now. Minimum clearance to combustibles for single wall pipe is 18". lining the wood wall with either cement board or sheet metal should be an effective heat shield. Don't forget about clearance to the pipe where it goes thru your roof.

A stack probe for stack temp should be about 12" from where it connects to the stove.

AUF will add another couple hundred degrees to your stack temp. With the blower on you would want your stack damper wide open or you will get smoke pushed out of the firebox.

As for if your stove pipe can handle the extra heat? Yea it should be fine. It might shorten the life of your pipe by a couple years but it's not going to melt it down in one season.

[Hunt4sap]

Cool thanks,

New thought about adding AUF fan

Doesn't this increase wood consumption tremendously?

My barrel has no ramp up in rear( like most commercially made evaporators)

My SS pan is just that, a flat stainless steel pan that measure s approximately 2'*4'* 4" deep( no flues )

It's real basic setup but if adding a fan can increase boil rate ( more than 5 gallons / hr)and my pipe can handle it i will try it and see what I can get out of this setup

Sounds like if pan is heated more with auf fan, pan only being 4" deep I might want to run deeper than I normally do ( 1")

What is preferred stack temp with auf fans?

[82cabby]

I ran a barrel evap with a blower for many years. With a well bricked, insulated and carefully monitored evap i could get 9 gph in my 2x2 pan. It takes a lot of tweaking to get it really ripping though.

[Cjadamec]

You will definitely increase your wood consumption. You will also be left with nothing but ash when the fire burns out not a coal in sight. Adding a ramp up to the stack will help improve your boil and shorten the fire box which should lower the wood used because you will have a smaller but hotter fire. Simply stacking up fire brick is all you need it doesn't have to be anything fancy.

Rigging up a pre-heater for your sap is another good way increase your boil rate by 10-20%. A pre-heater is my next improvement adding the cold sap and cooling my pans is killing me.

[steelguy]

I use the same size pan (2x4) only with dividers
have the AUF with the taper up to the back of my arch. seems to work really well, I can get 13-15 gph using split ash , keep pcs about the size of your wrist.
it does go through a LOT of wood, have to add wood every 20 mins.
I have a steam hood with copper tubing run around the insides to help pre-heat the sap, it gets it up to around 90-100 degrees, which seems to help a lot.

[maple flats]

The distance to Combustibles is 36" for wood burners on a single wall pipe. I suggest you either put up a heat shield rated for that, or just put up layers of tin spaced out 1" on non combustible spacers. Each layer thus spaced cuts that in half. Thus 1 layer yields 18", 2 layers yield 9".
As far as the stack goes, it can take the heat, but if you want a temp. probe put it at about eye level. It can even aid you in knowing the best timing to add wood by watching that temp.

[Hunt4sap]

Thank you all for your Insight I pulled my magnetic thermometer off of my stove in the house and just stuck it on the flue pipe for now when I'm boiling my temperature thermometer shows around 200 and 5 to 210 degrees and my stack is between 6 and 700 degrees 1 foot above elbow where it comes out of the back of the 55 gallon drum...

[wiam]

Thank you all for your Insight I pulled my magnetic thermometer off of my stove in the house and just stuck it on the flue pipe for now when I'm boiling my temperature thermometer shows around 200 and 5 to 210 degrees and my stack is between 6 and 700 degrees 1 foot above elbow where it comes out of the back of the 55 gallon drum...

Magnetic is a good start. Probe is more accurate.

[Hunt4sap]

17353
Magnetic thermometer worked well
Was more a quick visual checker for me to see how everything was burning in comparison to my sap pan thermometer...
4.6 gallons per hr(41.5 gallons sap from my last 1 day gathering)my largest amount ever ( only 2nd year sugaring)
Pretty happy with results so far this year from 3 gathering s(100 gallons of sap already!!!( This was my total amount in 2016)
Maybe a ramp in drum and a AUF fan to come soon, not sure if doing this year or not...
What is a guess on increase in boil rate by doing these two things to my 55 gallon drum burner?