Head Scratcher

[Eric Johnson]

I fired the EKO up this morning, kicked it into gasification mode and went inside to take a shower. When I was ready to leave for work, it was smoking. So kicked the burning wood around in the firebox, threw in a few more chunks, closed the bypass damper and got both nozzles lit off really good. Still smoking a little, though.

I'm guessing that there is a little creosote built up on the bypass damper which is not allowing it to close all the way, with the result that a little smoke is leaking up through the chimney. It can't be coming from the gasification chamber, which was full of flame when I checked it. My dealer said that for the first couple weeks of operation, this kind of thing happens. He said I might have to scrape the damper off to get a good seat. For reasons I don't completely understand, these kind of creosote issues disappear after the boiler has run a number of times, he says. I'm guessing it has something to do with the metal curing or breaking in, or whatever.

I know that if you overfire the boiler or try to operate it with the damper open, you can warp the damper, probably with similar results. I've never come close to overfiring this boiler because I've never put enough wood in the firebox to generate that much heat and I've never seen the water temp over 82. So I'm guessing it's either the creosote I mentioned earlier, or an air adjustment (cold this morning) or maybe just one of those days.

Does this theory make any sense? Anybody with a similar experience?

Which leads me to my second question, which is: Do you get steam coming out of the chimney in very cold weather? I wouldn't think so with dry wood, but I don't know.

 

[Nofossil]

I fired the EKO up this morning, kicked it into gasification mode and went inside to take a shower. When I was ready to leave for work, it was smoking. So kicked the burning wood around in the firebox, threw in a few more chunks, closed the bypass damper and got both nozzles lit off really good. Still smoking a little, though.

I'm guessing that there is a little creosote built up on the bypass damper which is not allowing it to close all the way, with the result that a little smoke is leaking up through the chimney. It can't be coming from the gasification chamber, which was full of flame when I checked it. My dealer said that for the first couple weeks of operation, this kind of thing happens. He said I might have to scrape the damper off to get a good seat. For reasons I don't completely understand, these kind of creosote issues disappear after the boiler has run a number of times, he says. I'm guessing it has something to do with the metal curing or breaking in, or whatever.

In two full seasons, I've never experienced anything that I'd attribute to the damper leaking. I've had only two instances of smoke after gasification was initially started:

1) With a reload containing big chunks of damp wood
2) With a reload containing a lot of easily flammable material when there wasn't a really good coal bed - it generated more smoke than could be burned in the secondary combustion. Solved itself quickly.

I know that if you overfire the boiler or try to operate it with the damper open, you can warp the damper, probably with similar results. I've never come close to overfiring this boiler because I've never put enough wood in the firebox to generate that much heat and I've never seen the water temp over 82. So I'm guessing it's either the creosote I mentioned earlier, or an air adjustment (cold this morning) or maybe just one of those days.

I'm going with the last two. Both of them. Together.

Which leads me to my second question, which is: Do you get steam coming out of the chimney in very cold weather? I wouldn't think so with dry wood, but I don't know.

Water vapor is a byproduct of combustion, even if the wood is bone dry. Wood isn't pure carbon - there's some hydrogen in there as well. That being said, I've only seen wisps of water vapor on really cold days.

 

[Corey]

I suppose I could see the metal surfaces building up a coating of soot, creosote, carbon, ash, rust, (or a combination of all) or anything else that may help the plates mate closer together over time. I've noticed in my stove that over time, little bits of fly ash have sealed some small gaps in the firebrick and other seams, so maybe something like that is going on in your boiler.

As for the steam - that sounds normal. Water is one product of combustion. Burning any type of hydrocarbon (HC) in the very basic unbalanced form can be written as:

HC + O2 -> CO2 + H2O

It's not uncommon to see steam out of car tailpipes, gas furnaces and other combustion equipment that is using a totally dry fuel, so I would expect it is pretty easy to get with wood, too. You might notice the steam even more if you are burning all the smoke - whereas a smoky fire may mask the steam somewhat.

Corey

 

[Eric Johnson]

Well, no smoke now, according to my wife. I should probably get a webcam and some remote controls so I can fool with the thing from the office. Probably like anything (or anybody) else: some days it takes longer to get up to speed.

 

[Nofossil]

Question: what do the fly ash deposits on the walls of your lower chamber look like? Mine get a very fine layer of dark brown soot during startup, but become lighter gray as the burn progresses. When I scrape off the deposits, it's a very fine and totally dry (non-clumping) powder that averages out to something like light brown cocoa powder. Same with the deposits on the inside of the HX tubes.

If I fail to get gasification going, I'll see a light layer of black soot along with really foul smelling wood gas.

I'm curious to compare and see if there are clues.

 

[Eric Johnson]

I'm getting good gasification. It generally burns clean and hot. Unlike you, I open the bottom door when it's in gasification mode and watch the flame to see how it's going.

If I fail to get gasification going, I get a face full of foul-smelling smoke. When that happens, I open 'er back up for a few minutes, kick the wood in the firebox around with a poker and it will take right off when I close the damper.

The deposit on the walls of the gas chamber I'd characterize as a light brown layer of fine dust, if memory serves. I haven't scraped the walls down yet. Since I have two nozzles, they don't always light off at the same time, so you can get fire coming out of one and smoke out of the other on liftoff. This morning they were both blowing orange and yellow flame, but I'm thinking I may have temporarily overwhelmed the still-cool nozzles with a little too much kindling. I use bark, and it smokes like crazy. First thing in the morning I'm not always at my most coherent.

 

[Eric Johnson]

I'm still noodling this one out, but I think I may be onto it this time.

It mystifies me that some mornings I get smoke for awhile even though there is a nice bed of coals in the burning chamber around the nozzles, and when I open the gasification chamber door, all I see is clean-burning gasification in progress. The smoke clears after about a half hour. As mentioned, I thought maybe my bypass damper was leaking slightly, letting some smoke up the chimney, despite the complete gasification going on down below.

Here's what I think is actually happening:

Since I don't have my tank running yet and I want there to be some coals in the boiler in the morning, I'll load the firebox up at night, knowing that on relatively warm nights the boiler is going satisfy the zones and switch to idle mode at various points during the night. This should deposit a small amount of creosote in the heat exchanger tubes and probably the chimney as well. I think that when I crank her back up in the morning, the the fire going into the hx tubes burns off the accumulated creosote, sending some of it up the stack as smoke. I doubt that the chimney ever gets hot enough to do that. Once the creosote burns off, we get the typical heat wave exhaust for the rest of the day.

This shouldn't be an issue in colder weather and with a tank, because I should be able to fire complete cycles without idling.

 

[TCaldwell]

Eric, when i fire up the garn and the outside temp is low, like the last few nights, initially i will get smoke, as the exhaust temp warms the distance from the top of exhaust pipe to the bottom of visible smoke increases and there is a noticeable top or end to the smoke, i believe at this point it is just condensing hot air? as the outside air temp lowers the longer this happens.