1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

What kind of stack temps do you have at full output?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by BoilerMan, Oct 14, 2012.

  1. BoilerMan

    BoilerMan Minister of Fire

    Joined:
    Apr 16, 2012
    Messages:
    1,524
    Loc:
    Northern Maine
    As some may have read my saga.... I am not able to get over 275F at the flue outlet of the boiler. This is measured with the electronic stack probe that can be displayed on the digital readout, as well as my cheapo magnetic burn indicator on the flue neck of the boiler. I feel this is way too cold, and thinking my wood is too wet to achieve full gasification. I am going to break down and buy one of those dumb kiln-dried shrink wrapped wood stacks @Lowes and make one last attempt to see what the temps will do with really dry wood. I may remove the turbulators and try also. I've burned several loads and seem to be having gasification as the refractory is clean and makes a good rumble, however I'm getting uncomfortable with the amount of shiney tar-like creosote on all the steel in the lower chamber and migrating to the firetubes. This is my first expierence with a gasser and also this boiler which by comparison uses much less wood, but is lack-luster in tar production. Post some stack temps y'all get with a normal fire and how long it takes to get there. I can get to 250F in about 10 min from a cold start, but no higher unless of course I open the bypass. Help me feel better about this large cash outlay wood burner upgrade, the old NY-WC 130 had much less of a learning curve when it was in place of the Attack, I controlled the draft to maintain 350-400 stack and never had ANY chimney buildup, just let the heat (and smoke billowing) right up the chimney and all was good!

    TS

    Helpful Sponsor Ads!





  2. jebatty

    jebatty Minister of Fire

    Joined:
    Jan 1, 2008
    Messages:
    4,256
    Loc:
    Northern MN
    Can your dealer give you any help on this? I don't think you ever should find any creosote-type deposits in the gasification chamber or the firetubes, at least I never have.It would be good to try some very dry wood and see what the result is, as moisture content could be your problem. If your are burning oak, my experience is at least 3 full summers of drying to get oak into low moisture content. Also, see if you can try different wood from a friend. Maybe a different wood or mix will perform better. And if you can, try increasing the air flow from the draft fan. Is their a damper or speed control to do this?

    I burn very dry pine and aspen (minimum 2 full summers of seasoning, in woodsheds), both of which burn fast and hot, and I have the homemade chain turbulators. Stack temps during high burn are 425F or so, and mine are probably higher than others. I should try a load of oak sometime and see what the result is. I don't have much oak and I save the oak for the woodstove in the house.This is the start of my sixth season of burning, no problems, so why change a good thing?

    I can adjust a damper on the draft fan to reduce/increase air flow and stack temp follows accordingly, but my Tarm really seems to "like" this temp range and it really purrs, or rather it roars. Also, I have a good 10' of black steel stovepipe, single wall, running up to the ceiling where it mates with the Class A, and although I haven't measured, I know the stack radiates quite a bit of heat into my shop and the stack temp likely is a fair amount less before it enters the Class A, another 11'.
  3. fahmahbob

    fahmahbob Member

    Joined:
    Jul 7, 2009
    Messages:
    84
    Loc:
    South Central Mass
    Depending upon what I'm burning, my stack temp at high burn is anywhere from 325-425. The lower temp is when I'm burning oak that's been drying about a year, the higher temp is from drier oak or year-old red maple. Last year I ended up burning some 6 month dried oak (stacked on my good stuff - long story) and I certainly had issues with 'sticky' turbulators, but that was before I had my probe thermometer so I have no idea what the temp was. I mixed that stuff with dry pine and it helped with the problem, but didn't make it go away entirely.

    Oh, and before I cleaned my heat exchanger tubes this spring I had temps close to 500 with dry red maple, but obviously dirty tubes is not how you want to raise your stack temp!
  4. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    3,659
    Loc:
    Nova Scotia
    It's only been a week since I started burning, but my burns seem to peak at around 200c, which is pretty close to 400f. When I started, I was only getting up to 150c or so, which is around 300f. I have removed 2 out of the three turbs to get there. Have you checked that your chimney draft is in spec with the manufacturer recommendation? I'm working with natural draft, so will use all I can get (within reason), but I'm kind of thinking too much draft might not be good with a forced draft unit? Maybe? If the wood turns out to not be a factor, and your draft is within spec - I'd try removing turbs one or two at a time and seeing what that does. Also, I'd think about getting a second thermometer in my pipe to make sure on the temps you're reading - or checking with an IR thermometer (they can be finicky too though). My magnetic guage always reads less than my dial guage, by a fair amount at the higher temps - I forget how much higher exactly but I'll check that out next burn.
  5. flyingcow

    flyingcow Minister of Fire

    Joined:
    Jun 4, 2008
    Messages:
    2,270
    Loc:
    northern-half of maine
    I always thought the magnet style stack temp gauges read lower than the probe type? if so, whats that mean for you?

    But, the tar creosote is troubling in your lower chamber, especially in the tubes. That being said, i have had, on a few occasions, a little "tar" drip out of stack after it leaves the boiler. Upon cleaning everything, no black stuff.

    just curious, from throwing the match, how long before the boiler gets to 165? and then 195? Should be in less than an hour to 165, than a little over an hour to 195?

    Sounds like your getting gassification. Didn't you say your wood is about 19%? Nice if it's drier, but that shouldn't be your problem. You mentioned Lowes, so you must be in the P.I. area. if you were down my way you could take a whell barrow load of my rock maple. But I think mine is between 15/19%.

    After an hour or so of burn, do you have any smoke coming out your chimney?

    My stack hits 250 pretty quick also. Runs about 400/450 during burn. When i see it pushing 600 I clean tubes.
  6. Gasifier

    Gasifier Minister of Fire

    Joined:
    Apr 25, 2011
    Messages:
    3,135
    Loc:
    St. Lawrence River Valley, N.Y.
    Taylor. My current stack temps are around 450-600 ::F. If I have good gassification then my temp is around 400. If I lose gassification because of a blow through my coal bed the temp will quickly rise to 550-600 ::F. Don't sweat this problem too much. I have been running my gasser for a little over one year now. (I burn all through the spring, summer, fall for DHW.)

    In the beginning I had some creosote problems. I took me a while to figure out how to solve them.

    First, you and Jim are correct that it may be in the moisture content. That was one of the problems I had with certain wood I was burning. Mixing in some dryer wood will help significantly, but not totally eliminate it. Once I got to the point of burning all dry wood and leaving the stuff with a higher moisture content until it is dry, I had no more problems in the boiler. Luckily I always have White Ash stacked outside. The stuff dries fast and throws good BTUs.

    Second. I determined that I was losing too much heat through my single wall stove pipe and by the time the venting happened at the top of my 27' chimney it was not hot enough. That resulted in creosote and moisture running down the chimney. To make a long story short on this one, I switched my pipe inside the boiler room over to double wall, insulated S.S. and have had no problems since then.

    Third. You and others may not agree with this, But. If you are having the problem because of moisture content and you do not have any other wood available. Here is something you can try. Just like in a wood stove or regular boiler, the smaller the split size is the more surface area you have for catching on fire. This results in a hotter fire. So if you have to, split your higher moisture content wood into smaller pieces. I found that it helped to get the fire hotter.

    Fourth. Another type of wood to burn is free pallets. Now yes, it is more work, and a pain in the ass sometimes. But, if you take your time, listen to some tunes, and break some free pallets down, you can burn this wood for now while your other wood dries. You can also mix this in with your higher moisture content wood, say 40% pallet wood with 60% higher content wood. You may even split some of the other wood a little smaller so it dries out quicker while you are burning some pallet wood. I like to split wood by hand just for the exercise. Well, to a certain extent. So three or four nights a week I would go outside and spend 20 minutes and split some of my wood into smaller pieces. Using a large heavy round to set the splits on and hit them with a maul does a nice quick and easy job. Then I would bring these splits into the boiler room and stack them. They would be there for a week or more. Keeping this rotation going helped the wood to dry out even further before it went into the boiler. Did I mention the pallet wood was FREE!

    Fifth. Sorry for the novel. ;lol I get a little to talkative sometimes. ;hm

    ;lol Have a good one man. And keep us posted on your problem.
  7. Clarkbug

    Clarkbug Minister of Fire

    Joined:
    Dec 20, 2010
    Messages:
    969
    Loc:
    Upstate NY
    You could always grab some biobricks if you can get them, or some cheapie framing lumber, which might end up being cheaper than the little plastic wrapped bundles. 2x4 will burn hot and fast, and you would definitely see what the top end of heat production would be.....
  8. Gasifier

    Gasifier Minister of Fire

    Joined:
    Apr 25, 2011
    Messages:
    3,135
    Loc:
    St. Lawrence River Valley, N.Y.
    This is what I heard too. And it seems to hold true. The temps that I am giving are rough. I am only using a magnetic thermometer on the outside of my single wall pipe just when it comes out of the ash cyclone. Really good gassification and I can have an outside temp of 150(inside 300), without gassification I have seen 325(650) on the outside of the pipe. Knowing that temp can be twice on the inside of the pipe, as pointed out to me in my first year of burning in my gasser;lol, I know about where it is. Now I can usually keep the outside of pipe temp around 175-275 (inside350-550). Unfortunately I can not baby sit my boiler all day and make sure I have gassification all the time.

    Hey. Check out this thread and read down to where you can see three different types of thermometers in one picture. Cool comparison.

    http://www.hearth.com/talk/threads/had-to-join-you-guys.90746/#post-1206064
  9. wardk

    wardk Member

    Joined:
    Jul 19, 2012
    Messages:
    179
    Loc:
    B.C. Canada
    I'm new to this too, I have found 350 to be about right . Have seen higher like 475 with very dry pine cause the boiler to puff,manual says use a brick to control airflow, works great. I think 250 is a little low unless the exchangers have taken that much heat off the flue gas to heat the water. What does the bypass bypass?
  10. JP11

    JP11 Minister of Fire

    Joined:
    May 15, 2011
    Messages:
    1,098
    Loc:
    Central Maine
    Put me down as a ditto of 350 being the sweet spot.

    You need to remove every variable you can. Get some KNOWN dry stuff. Like bio bricks.. or a neighbor that's had something under cover for years.

    Just starting to read your post.... like SO MANY on here. I was yelling at the screen after the first couple sentences.. IT'S the WOOD!!!

    It so often seems to be the cause of 95% of the problems on here. Hang in there, the folks on here will get you straightened out. You may, or may not have any hair left by the time it's fixed though. :)

    JP
  11. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    3,659
    Loc:
    Nova Scotia
    Gasifier, are you sure you were getting creosote?

    I'm new at this gasifying stuff, but I have always understood that gasifiers burned up all the creosote-forming stuff, so there would be nothing left going up the chimney to make creosote?
  12. Eric Johnson

    Eric Johnson Mod Emeritus

    Joined:
    Nov 18, 2005
    Messages:
    5,705
    Loc:
    Central NYS
    Contacting the dealer is a good idea. Sounds to me like perhaps your air adjustments are out of whack. Forgive me if you've covered this already, but have you played around with them yet?

    My only advice is: don't panic. These are more complicated devices than a conventional wood fired boiler, and there is an invisible learning curve, as well as the machine breaking in and performing correctly. The one wildcard with any wood burner is the condition of the fuel, which is a variable you generally don't have to contend with when burning fossil fuels. All I can say is that it took me awhile to get my rig to do what I expected, and yes, I had some unjustified buyer's remorse at times.
    woodsmaster likes this.
  13. Gasifier

    Gasifier Minister of Fire

    Joined:
    Apr 25, 2011
    Messages:
    3,135
    Loc:
    St. Lawrence River Valley, N.Y.
    Yes. When I was burning wood with too much moisture in it I did get creosote. That was my fault. In the early part of my first winter season with the gasser, last winter, I was throwing in some wood I just wanted to get burned up. Mistake. To high of moisture content is not a good thing. Yes the boiler would burn it up in the firebox. But better to not have it. Now as far as the chimney went, I sure did have creosote. My chimney goes up 27' after it goes through the wall. That is a lot of cooling time by the time it gets up to the cap. After I learned a few things, takes me a little while sometimes ;lol, I called my chimeny sweep guy because I could see the creosote on the chimney cap. He came and cleaned my chimney out top to bottom. There was quite a bit of creosote. I don't like any of it. Period. I had never had any creosote in the chimney when I burned my wood stove. That was because my stack temps were much hotter.

    So, like I said. I changed my inside pipe from the pain in the a.. single wall pipe, with joints that leaked that had to be sealed with high temp caulk, etc, etc, to the double wall insulted s.s. and the problem has been solved. I also did away with all that b.s. horizontal pipe for clean out purposes and sloped it up to the wall from the ash cyclone. Heat goes right up quicker, any larger pieces slide back down the pipe right down into the ash cyclone. Works much better.

    Oh sh!t. I started another novel. Sorry.;em
  14. kopeck

    kopeck Minister of Fire

    Joined:
    Mar 24, 2011
    Messages:
    524
    Loc:
    Maine
    400 F is where I run. The temps climb as the tube get dirty. When I see temps over 55o F it's time to clean to tubes.

    K
  15. BoilerMan

    BoilerMan Minister of Fire

    Joined:
    Apr 16, 2012
    Messages:
    1,524
    Loc:
    Northern Maine
    Ok, this thread took off fast! LOL, for all who asked, in my OP I have an electronic stack probe (factory), and also the cheapo mag thermometer, both read within 25F of each other. I also have an IR and that reads somewhere in between the two, so I know I'm in the bleachers of the ballpark on the temp reading. My chimney is 6" class A at 24 feet from the boiler flue collar, all straight up. My water temps go from room temp to 190 (with no load) in about 25 min. The boiler capacity is 47 gallons...... So heat output seems pretty good, it's just the low stack temp and I don't want to gunk this thing all up. I just brought home two of those EXPENSIVE kiln-dried shrink-wrapped firewood-for-idiots from Lowes. I'm gonna light those in there and see what happens. Thanks for the responses, I'll keep you posted.

    Oh, ant BTW the majority of what I have is Beech, with some Yellow Birch and White Maple mixed in. I cut it all last fall before the frost. Split and stacked it all in March. Most splits are around 18% with some as high as 21%
    TS
  16. Eric Johnson

    Eric Johnson Mod Emeritus

    Joined:
    Nov 18, 2005
    Messages:
    5,705
    Loc:
    Central NYS
    I wouldn't get all obsessive on the stack temp, Taylor. Mine has been all over the place and I've never had any creosote in the stack. Maybe a little soot, but nothing like you get with a wood stove or non gasifying boiler. If you're getting the heat out of it, relax and enjoy. You'll know soon enough how it's going to heat your house.
  17. flyingcow

    flyingcow Minister of Fire

    Joined:
    Jun 4, 2008
    Messages:
    2,270
    Loc:
    northern-half of maine

    you've got a different boiler than i have. So I haven't looked at the layout of yours, obviously. What you have for wood mc isn't bad. But just because you're stack temp on the unit says it's 275f, doesn't mean it's calibrated right. Just a thought, i am very seldom right. I married an Irish lady. Why argue? Sorry off topic. But i think your boiler is running good? Back to my thought....if the magnetic type of stack temp(which usually way lower than probe type) is matching the digital readout......IMO jack azzed opinion...somethings off with the digital readout?

    Also, you're going to burn kiln dried wood....different first and secondary settings on your boiler vs waht you are burning now.
  18. Woodsrover

    Woodsrover Member

    Joined:
    Oct 15, 2012
    Messages:
    111
    Loc:
    Northwest Connecticut
    After a total of 4 full days of burning my new Woodgun and can report a stack temp of around 275 at full burn. That's with a cheapy bi-metal thermometer so actual temperatures my vary. Seems funny after seeing 350-400 out of my woodstove for so many years but there it is.
  19. BoilerMan

    BoilerMan Minister of Fire

    Joined:
    Apr 16, 2012
    Messages:
    1,524
    Loc:
    Northern Maine
    Well the KD stuff didn't burn any different (although my wallet was burned). The highest I've been able to get the stack is 275F and that was with the water at 190F and a high bed of coals. I've had some bridging and get quite a few blowholes in the coal bed, how do you guys avoid this? I've been burning 4-5" splits and still get blowholes in the coal bed. Is it normal to have tar-creosote on the upper chamber walls?

    I ran an underdraft conventional boiler in the same place and never had creosote on the walls of the boiler, I also burned hot and hard and cleaned everything to as-new monthly. Let me know if you want pics of anything.

    TS
  20. Nofossil

    Nofossil Moderator Emeritus

    Joined:
    Oct 4, 2007
    Messages:
    3,398
    Loc:
    Addison County, Vermont
    For me, the real question is whether you're getting good secondary combustion. If your secondary chamber has a coating of very light brown or white ash, then relax and enjoy. If it's dark brown then I'd work on getting a burn with really good fuel as a benchmark.

    My flue temps run around 450 (internal probe). I have a small boiler with pretty short HX tubes.
  21. goosegunner

    goosegunner Minister of Fire

    Joined:
    Oct 15, 2009
    Messages:
    1,230
    Loc:
    WI

    How close to the boiler do you measure your stack temps?

    gg
  22. maple1

    maple1 Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    3,659
    Loc:
    Nova Scotia
    If your magnetic stick on guage is reading the same as your probe thermometer, which is also close to your IR gun (I think that's what you said?), I would suspect your probe thermometer. This is likely a dumb question, but are you sure it's reading F and not C? My Euro boiler came with a C guage - but maybe yours reads both anyway.
  23. henfruit

    henfruit Minister of Fire

    Joined:
    Nov 27, 2007
    Messages:
    710
    Loc:
    New Hampshire-Maine border
    Creosote in the upper chamber is ok.That is where you are taking the wood to 600 degrees and turning it into a gas and then pushing it through the nozel hitting it with secondary air and igniting it.It seems with low stack temps that you are extracing the heat in to the water very good.As long as you are not condenseing in the smoke pipe you should be fine.
  24. kopeck

    kopeck Minister of Fire

    Joined:
    Mar 24, 2011
    Messages:
    524
    Loc:
    Maine
    I'm wondering the same thing as maple1. My Tarm reads both but the primary numbers are a Celsius.

    275 c would be 527 f, which would be a bit high but in the ball park IMHO.

    K
  25. BoilerMan

    BoilerMan Minister of Fire

    Joined:
    Apr 16, 2012
    Messages:
    1,524
    Loc:
    Northern Maine
    Temp is measured at the steel flue collar. Cheapo magnetic thermometer, confirmed with IR thermometer. In the first image you can see the stack temp probe in the upper left part of the manifold. Notice the bypass damper and hor wet-looking the creosote is, also some in the firetubes. It is not stickey, but man I don't like it. I'm starting to miss my old smoke dragon, chalk it up to buyers remorse, I just want to get this thing running well and happy about the cash and time I spent doing the install.

    TS

    Attached Files:

Share This Page