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Summer time burning

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by sparke, Jan 6, 2008.

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  1. sparke

    sparke Minister of Fire

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    Looking for opinions:
    Which gasifier boiler do you feel would perform better in summertime for DW?

    Eco/Tarm type or Seton/Greenwood type?

    Thanks

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    I'm planning to run my EKO this summer for DHW. With the 1,000 gallon tank, I'm thinking once a week, more or less. But I've never done it, so we'll see. Kind of like summer today--40 funloving degrees out. And yes, I've got the boiler going.
  3. webbie

    webbie Seasoned Moderator Staff Member

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    Keep in mind that most summertime burning - unless at full bore into storage, can shorten boiler life by causing heavy-duty acids to form. A lot of the early gasifiers (Eshland and even some Tarms) sprung leaks due to this.....so go with storage and hot burns or else shut it down.... and maybe hang a light bulb in the box to avoid condensation.
  4. wdc1160

    wdc1160 New Member

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    EKO owners anyone of you have problems with ash/moisture becoming caustic from long downtimes??
  5. Nofossil

    Nofossil Moderator Emeritus

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    Not that I can detect. I shut down from about April 1 to October 15 and heat my storage tank with solar.
  6. webbie

    webbie Seasoned Moderator Staff Member

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    FYI, these problem tend to occur 4-8 years down the road....so unless anyone has been using the units for a couple years you may not find out much. I do remember some units suggesting the light bulb hung inside!
  7. drizler

    drizler Minister of Fire

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    By acids and corrosion you mean for where, inside the chamber or the boiler tank inside where the water is. I am thinking in the stove innards where the ash tends to lay correct?
  8. webbie

    webbie Seasoned Moderator Staff Member

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    Problems I have heard of are from the inside of the firebox - not from the inside of the water. But I suppose it is possible from either side, although "black water" does not tend to corrode.
  9. wdc1160

    wdc1160 New Member

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    I specifically was referring moisture combining with wood ash. I am not concerned with water corrosion.

    A percentage of ash left. I am not sure how much. Someone if you can help out?
    is made up of potassium hydroxide. This combines with water and is very dangerous to regular metals.
    Most gassers now have either ceramics or one of many types of stainless to make sure the life of the boiler
    is long.
    from my research normal boilers don't have as many problems with this because they don't have an air tight seal on the combust chamber. Apparently the caustic solutions in a normal combust boiler must evaporate, disappate, or just dilute.
    I thought most modern gassers had better materials for this now then 5 or 10 years ago.
  10. Eric Johnson

    Eric Johnson Mod Emeritus

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    It's still quarter-inch boiler plate, basically. Keeping your return water temps up and burning hot fires seems to be the key. A couple of gasifier mfgs. use ss, but not many. Any way you look at it, solid fuels are rough on any boiler. Compare basically static output and uniform combustion conditions with an oil or gas boiler to the ups and downs you see with a wood boiler--plus the wear and tear involved in tossing chunks of wood (with inconsistent moisture content and varying chemical composition) into the firebox and regularly exposing it to fresh air, and you begin to sympathize with the poor machines. It's a tough life. Not to mention when teenagers or inlaws load the boiler. Do you think they care about "ringing the bell" when they toss wood into your rig? Keep the bastids away, I say.
  11. wdc1160

    wdc1160 New Member

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    This is the reason I don't have a gasser right now. Fear of condensation during cold temps mixed with potash. Many people I consider pros in the consumer gassification field swear that it can take out a boiler in 5 years if not operated during cold weater continuously(we will say 5 times a week). This thread got started by discussing summer weather being the cause, but winter was what I was warned against.

    No doubt the solid fuel boiler has to be the toughtest of all the appliances, but I think its biggest enemy is condensation mixed with ash - IME, Not ringing the bell. Although I don't know your inlaws.
  12. drizler

    drizler Minister of Fire

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    I am sort of surprised they don't have some sort of procedure, additive, spray or whatever to address this. I am sure the stainless would go a long way towards an answer. On the other hand thick plate goes a long way towards solving corrosion in my experience with rust on machines, cars ect. Thick steel and cast iron like my 1949 Cat dozer can just sit there exposed for decades while thin sheet metal just goes to hell in a few years if the paint is nicked. Of course its not a direct comparison but still pretty applicable considering how nasty road salt is. How replaceable or able to be welded are those boilers innards anyways? This is all the stuff I want to know in my quest for knowledge in these things before I take the plunge. My multifuel pellet stove is starting to show some rust and you are right in that it seems to all form in the Summer months. Last year I started smearing motor oil on the innards. Luckily with my stove its easy to get in there and put some more meat on its bones if it starts to get thin. How about those boilers???
  13. wdc1160

    wdc1160 New Member

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    I have spent some time looking into this. It had almost stopped me from getting a gasser.
    To put it in perspective on a scale of 1 to 10. road salt or the "saltiest parts of the ocean" is a 1.6. This is about an 6.
    Or about the equivalent of 20 percent mixture of Hydrochloric water solutions.

    And, I know the potassium hydroxide compound isn't rare in fire's ash, because they have used it in numerous civilizations across the world with all types of wood.
    I have never read anywhere it could be quantified as a net amount of potash you could expect from an amount of wood.

    I said caustic. It actually an strong base -- "like an acid".

    Obviously part of the solution is remove all of the ash -- sorry to state the obvious. That removes the danger, but it is impratical to have to be present at cool down. Or to clean out the thing every time it gets cold. I was told if you going to leave ash in the stove cold,then open the loading door to prevent a moisture seal.


    Did the oil help?? I will say again sealed combustion chambers in the winter atmosphere w/ intermittent use are what I was warned against; Not long term summer downtime

    I made a call and here is how it was explained. You have a piece of metal and this is how it spends one day in the winter. starts out at 12pm at 0 F then heats up to 1000F by 2pm, is covered with caustic ash(unknown amount)-- cools to 40F at 12 am moisture held air tight against the steel while mixing with ash.
    I think now the rapid/extreme heating and cooling may play a role in this as well
  14. Nofossil

    Nofossil Moderator Emeritus

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    I've been on the lookout for this phenomenon, and all I can say is that after 2 1/2 seasons, the steel plate on the inside of my secondary chamber and the HX tube area is still smooth and clean. No pits, no scale, no sign of corrosion. The steel in the primary chamber is covered by a layer of baked creosote, but is also smooth and unpitted.

    I'm hoping that this is a non-issue for boilers operated the way that I operate mine.

    I'm contemplating a control change that would shut down the fan sooner when th fire has essentially burned out, and turn on the circ to scavenge the leftover heat. One of my concerns is that I might then be creating a condensing environment.

    By the way, none of the steel plate sees anything like 1000 degrees. It's backed up by 180 degree water. It does have gases that are even hotter than 1000 degrees on the combustion side, but the surface of the steel doesn't get anywhere near that hot.
  15. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    Just restating the question in case anyone got lost up there ;-)

    I used my GW for spring and fall (not summer though). I built a hot, small fire at night. Once the HX heated the oil boiler, I heated the DHW to 145. Then I let the small fire die. In the morning there was ample DHW for showers and a load of laundy/dishes. Any standby losses from the inside boiler and/or DHW tank were great for warming the basement slightly.

    My intention is to go with storage and use solar for the summer. What I am still fighting with is how to ELIMINATE standby losses on the storage in summer, as we do not have central AC.

    Jimbo
  16. Nofossil

    Nofossil Moderator Emeritus

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    My strategy was to put the storage tank outside ;-)

    Seriously, that may make your life easier in other ways as well. In any case, you'll want to insulate the heck out of it. There are a couple other threads that discuss tank insulation.

    I also overheat my DHW tank - all the way to 160 degrees. I use a pair of mixing valves to stretch it out as much as possible. I have a writeup on my site.
  17. wdc1160

    wdc1160 New Member

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    The orgin of the moisture seems to be what the stove manufacturers and people I know who have seem think can be avoided, and the reason why normal boilers go much longer with no effects.

    Let me make some statments that maybe counter intuitive, but I think true. Correct them if you know I am wrong.
    because I am certain I am the guy who gets his steel plate ate through in three weeks.

    1. If you shut down the fan "early", you can only trap moisture. Cold winter air has less absolute humidity then the dryest deserts.
    1.5 absolute humitiy is what effects chemical reactions.
    2. If your wood is in optimal burning dryness, any trapped wood fumes would with out doubt have more moisture than can be absorbed by the winter cold.
    That is. you burn your wood, the wood is 80 percent wood 20 water. You burn 8 lbs of wood during this burn. You have 2 lb of water in your combust chamber.
    Water doesn't burn, so the water must be released. At the end of the burn you kick off you fan. you trap some relativly high amounts of moisture.
    3. you can't burn wood, without making "potentially" caustic checmicals-- have to add water.

    Very possible. Also don't forget it could be the fuel too.
    I think it goes back into how it is operated. It is unfair to say that the moisture is trapped, because what if the mosture leaves early in the process- nearly completely in the first hr of combust. It seems to me that if we are looking at very hot temps that could be the case. It makes another good arguement for storage vs idling.

    I figure it could have to do with green wood or a the species(because of the amount of pot. oxide) of wood as well. On this forum most of the gassification guru's seem to know how to get the fuel to optimum and are not burning 50% moisture in their wood; Hotter fires with less moistuer.

    The explanations that I have. I stole most of this from people who know more than me about this.

    I am going to chalk it up to dramatic liscense for the story. LOL. Your right, I was making a generazation about all gassers. Some don't have any exposed steel.
    I think this effect also has effects on parts that aren't steel like ceramics and all the funny material types that go into these gassers. Certainly steel is the most vunerable material and it shouldn't reach those types of temps under normal circumstances.
  18. Eric Johnson

    Eric Johnson Mod Emeritus

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    The water content certainly is a major factor in any woodburner. As you note, 20% is still a lot of water that needs to be exhausted. I was reminded of this during our recent below zero snap, when I saw the steam plume coming out the stack after firing the boiler up in the morning with very dry wood. But based on that, I'd say that most of the moisture is expelled at the beginning of the cycle. Doubt there's much moisture left in the firebox at the end.

    As I suggested in another thread, another reason for the premature failure of wood-fired appliances, compared to their fossil fuel counterparts, is that fact that you're dropping more than 100 pounds of raw wood into the combustion chamber every day--usually a couple of times a day--as well a changing the atmospheric conditions in the firebox every time you open the loading door. How many times can that backplate get banged with a big chunk of wood before the welds crack or the plate itself cracks? I'm very careful, but occasionally even I will "ring the bell" when loading wood. Ouch! Ever seen a teenage boy load a boiler? Keep them the hell out of the boiler room, is all I have to say on that.

    I have also heard that with combination units sharing the same firebox, you can get sulfuric acid from the sulfur in the oil and/or coal and the water in the wood. Maybe not in a few years when the sulfur content of domestic heating oil drops dramatically, but it's something for combi owners to think about--particularly if they have masonry chimneys. And then there's always low return water temp corrosion which, I believe, is a bigger problem in gasifiers than in conventional wood-fired boiler designs.
  19. Nofossil

    Nofossil Moderator Emeritus

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    In a desperate attempt to steer this back on-topic, I would suggest that the best boiler for summer DHW is the smallest one that you can get, combined with enough storage to last for many days.

    A typical household uses 60,000 BTU or so of hot water per day. If you can store 420,000 BTU of usable heat, then you can get by with one fire per week. With an 80,000 BTU boiler, that fire would only need to be about 5 or 6 hours long.

    I'd heat the storage directly, not through an oil boiler, and I'd use larger / lower temp storage to preheat the ice cold incoming water before introducing it into my smaller higher-temp tank.

    With solar hot water panels, you might need fires only in the fall when the sun angles get low.
  20. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    I actually would like to do two storage tanks . . . one out in the building with the GW (to avoid summer standby losses heating the residence) and one on the basement next to the oil boiler (to capitalize on the standby losses the rest of the year). But that would seem to require ANOTHER 90' of Thermapex and more excavation. . . .
  21. Nofossil

    Nofossil Moderator Emeritus

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    For DHW, remote heat storage is almost useless. The only thing you can do with it is use it to heat the actual DHW tank through the use of a circulator and a heat exchanger. You can't use the heat directly, and you can't use it to preheat the cold water before it enters the DHW tank. Even in doing 'batch heating', you lose the heat in the lines between tanks every time.

    The problem is that DHW use is intermittent, and usually isn't enough to even flush the cold water out of the lines between the DHW tank and the remote storage.

    My outside storage tank and my DHW tank are literally less than 24" apart to minimize this problem.
  22. sparke

    sparke Minister of Fire

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    Thanks All. And Thanks Nofossil for getting back on track lol. My question was wich type of gasifier would perform better in summertime. I bit the bullet today and bought a Greenfire. It is basically built like a Seton/Greenwood. Now the fun starts. I gotta rip the old boiler out and put this baby in this weekend. After that I will spend many more hours studying storage. I hope to build a tank and install a solar collector this year. Thanks all for your wealth of knowledge. I am glad to find a group of people just as sick as I am when it comes to harnessing fire!!
  23. Eric Johnson

    Eric Johnson Mod Emeritus

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    Just to pick up where nofossil left off, there's really no ash to speak of on the walls of my gasifier. There is some sitting on the refractory mass and the nozzles, and in the ash pit, of course, but most of the exposed steel backed up by water has a coating of creosote, not ash. Seems to me that you'd see any damage first on the stovepipe connecting the boiler to the chimney. There you get plenty of fly ash. Or on the turbulators, which are basically always coated with fly ash and exposed to any moisture exiting the stove during operation. Presumably, these parts would rot out long before the pressure vessel became compromised from the same forces.

    But there's no welding a leaky boiler, tru.dat.

    To restate what I said earlier, my understanding is that low temp return water corrosion is the big worry, and that's when the boiler is operating. If condensation during long periods of inactivity (say all summer) is a concern, it seems to me that the lightbulb idea is a good one, as well as maybe draining the boiler and disconnecting the chimney connection would be prudent as well. I can virtually guarantee you that no special precautions (including low temp water protection) were taken with my previous wood-fired boiler, and it was still going strong after 25 years when I got rid of it. It was a steel plate, wood-fired boiler full of ashes pretty much at all times.

    Finally, why would an idle boiler in the winter be more susceptible to corrosion than one that is idle in the summer. I know I typically fire my boilers up around September or October and basically run them steady until the following spring.
  24. wdc1160

    wdc1160 New Member

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    Eric, I am afraid that I either mistyped. Or, your mistaken in what you read. Because I didn't mean to give you the impression that this caustic chemical is created imediatedly after combustion. I meant to say this ash/creasote combining with water is supposedly bad stuff. Like if you boiler condensates during cold weather with ash in it.
    I assume all boiler's have an ample supply of ash and creo in winter -- not nessarily so in summer. In winter it is easy to condensate flue gases at the end of a burn. Or from the air maybe if it is in your house -- almost like a sweating window.

    Not eay to condensate with a stove in the summer. Unless you refridgerate your stove.




    I think Dead Btu's should grab some of his Goo and give it a litmus test. I think it could put this to bed.

    Can you tell me what type of low return temp corrsion is your primary worry. Is it in the summer?
  25. Eric Johnson

    Eric Johnson Mod Emeritus

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    No, the low temp return water corrosion I'm talking about happens when your return water goes below about 120 degrees. What happens then is that you get condensation on the back wall of the firebox and the combustion products eat away at the steel. Over time, it gets paper then. Then, one day you toss a chunk in too hard and it cracks. Time for a new boiler. Apparently it's a big concern with wood gasifiers, but also a potential problem with any boiler--wood or fossil fuel. Most people put mixing valves down there to keep the return water temps up. I have a 007 wired to my controller that pumps supply water into the return when the boiler is below a certain temp (140, I believe).

    I'm pretty sure that goo coming out of the backs of those Seton-style boilers is liquid creosote. It sure looks like it to me.
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