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Thread: Air Under Fire in a Barrel Evap - Pipe Size?

  1. #1
    Join Date
    Dec 2020
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    Morrisville, VT
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    Default Air Under Fire in a Barrel Evap - Pipe Size?

    I'm in the process of rigging up some air under fire in my barrel evaporator. Would like to plumb the air in from the back of the barrel via some 4" flex duct and a variable speed duct fan, and then with some 2" black iron pipe (1.5" ID, about 3.5 feet or so) into the barrel, and that pipe will have a bunch of holes drilled into it. Any thoughts or concerns whether that 1.5" line will be able to deliver enough air to run as hot as I'd like? Could probably go to 2.5" if I needed to, but 3" feels like overkill.
    2020 - 7 Late Taps, Open Fire, 1 qt
    2021 - 25 Taps, Barrel Evap, Bucket RO...Fever Setting In! Made 2.5 gal
    2022 - 30 Taps, 5 gal
    2023 - 30 Taps, Blower Fan, Insulated Evap

  2. #2
    Join Date
    Mar 2021
    Location
    SW Wisconsin
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    46

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    I would think the 1.5 would be fine. due you already have the 1.5 pipe on hand? if you have to buy it how much more would the 2.5 cost?

    I'm not a expert at all and hoping to next year put AUF on my 2 barrel stoves as well. for this year I have AUF on my home basement stove which is just 3 computer fans set in the ash tray blowing air into the fire box.
    Y1 9T ground stove/35 barrel stove
    Pics https://www.garagejournal.com/forum/...266239/page-23
    Y2 15T Basement stove 3 pans 35 barrel/add fisher stove/add 55barrel stove
    Pics https://www.garagejournal.com/forum/...266239/page-28
    Y3 20T Y2 Stoves plus 55 barrel
    Pics https://www.garagejournal.com/forum/...266239/page-36
    Y4 25T Y3 stoves in small shack
    Pics https://www.garagejournal.com/forum/...266239/page-44

  3. #3
    Join Date
    Feb 2023
    Location
    NW Ohio
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    I am doing the same thing, adding a blower to my evaporator. I think I am going to use 2 inch exhaust pipe.

  4. #4
    Join Date
    Jan 2006
    Location
    Oneida NY
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    11,681

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    I'd suggest you use some 24 ga stove pipe in 3" or even 4". Back when I added AUF I used 4", then I had 3 rows of 5/16" holes spaced about every 3", one row top enter, and one each facing the outer edges of the grates. Even though mine was high pressure, I suggest you also drill 5/16" holes, put a cap on the end and come in thru the ack and stop 6" short of the front. If your blower won't blow effectively, try 3/8" holes. You can lay the 4" pipe on the bottom of the barrel, and you might need to brush ashes off the holes before you fire up each day. With high pressure air I only needed to brush to clear the rows of holes about every 7-10 days, but a squirrel cage type fan won't have the force to keep the holes pen as well.
    Dave Klish, I recently bought a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  5. #5
    Join Date
    Apr 2013
    Location
    Northeast Vermont
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    i did similar to MapleFlats when i had a little home made 4'x5' evaporator. 3" stove pipe, plugged at the end. with 5/16" holes drilled in 3 rows the length of the fire box. now i have a 2 1/2 x 8' and just have a 4" stove pipe that goes to a 4" to 5" elbow that points up into the fire box... with no holes drilled. that works well also. i advise blocking off the front of the grates near your door so the ash doesn't blow up the front and out the door.
    Awfully thankful for an understanding wife!

    “The only place success comes before work is in the dictionary.”
    - Vincent “Vince” Lombardi

    Good luck to all!

  6. #6
    Join Date
    Feb 2018
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    Central, Wisconsin
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    I do it a little different. I have a barrel stove with a 24" x 18" flat pan. This makes a 24" long fire box. The fire box is lined with fire brick, and there is not any grate. I build the fire right on top of the brick. I have a 2" iron pipe that comes in on the brick from the back of the barrel, it extends into the fire box a couple of inches and blows directly into the fire. I call it air into fire, it works great. I use a squirrel cage blower from a gas water heater. I do modulate the blower speed based on stack temperature.

  7. #7
    Join Date
    Apr 2013
    Location
    Speyside, Ontario
    Posts
    271

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    I use a bathroom fan with a 3" outlet. I use 3" galvanized pipe straight from the bathroom fan, through the back of the barrel, at the bottom of the barrel, and shoved against the front of the barrel to seal it. Then brick goes up the sides of the barrel and a grate over the pipe. I have a bunch of 3/8" holes drilled in the galvanized pipe under the grate. I have a fan speed control to control it.
    2015 - 8 buckets, 332L sap, 8.5L syrup - Barrel evaporator, 2 steam pans
    2016 - 8 buckets, 432L sap
    2017 - 10 bags, 470L sap, 9L syrup
    2018 - 20 bags, 1050L sap, 17.6L syrup
    2019 - 20 bags, 970L sap, 22.2L syrup
    2020 - 17 bags, 813L sap, 17L syrup

  8. #8
    Join Date
    Dec 2020
    Location
    Morrisville, VT
    Posts
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    Thanks all for the encouragement and affirmation. Good to know I'm in the ballpark. Here's what I rigged up over the weekend, a section of 1.5" nominal black iron with 5/8 holes drilled under the grate. 4" duct on the outside connected to a variable speed fan. I was reluctant to go bigger with the black iron and reduce the size of my firebox. Note the 1" ceramic insulation is also new (firebrick was always there). Hope that the hardware cloth holds up. Pretty excited to see what a difference this makes compared to last year when it was uninsulated and natural draw, and I topped out at about 4.5 gph.

    maple2.jpg

    maple1.jpg

    maple3.jpg
    2020 - 7 Late Taps, Open Fire, 1 qt
    2021 - 25 Taps, Barrel Evap, Bucket RO...Fever Setting In! Made 2.5 gal
    2022 - 30 Taps, 5 gal
    2023 - 30 Taps, Blower Fan, Insulated Evap

  9. #9
    Join Date
    Apr 2019
    Location
    Nashville, MI
    Posts
    971

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    I doubt that the hardware cloth will last. What did you make the grate out of? It really looks heavy duty.
    2004 - 2012 2x3 flat pan 25 to 60 taps
    2012 2x3 new divided pan w/draw off 55 taps
    2018 - didn't boil surgery - bought new evaporator
    2019 new SML 2x4 raised flue high output evap. 65 taps
    made 17 gal. syrup
    2020 - only put out 53 taps - made 16.25 ga.l syrup
    2021 - Didn't work out
    2022 - 25 taps on bags / 8 taps on 3/16's line - late start

  10. #10
    Join Date
    Feb 2012
    Location
    Fond du Lac, Wisconsin
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    1,094

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    You can always drill more holes if you do not get enough air. The wire should be gone on the first boil if you have enough air. It looks like you used angle for your grate. Make sure that the angle is like V and not with the point going up. This will fill with ash and protect the angle, otherwise it will burn up also.
    Smoky Lake 2x6 dropflu pans and hoods on homemade arch
    Smoky Lake 6 gallon water jacked bottler
    Concentric Exhaust
    250 Deer Run RO
    325 taps

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