Solutions For EKO "Puffing"

[Medman]

THe EKO has been running for over two months. I have most of the bugs worked out except this one:
Occasionally after loading wood onto a bed of coals and letting it catch, then closing the bottom door and bypass damper, the EKO will puff a little smoke out of the draft fan.

Now, I have followed all of the Fine Tuning guidelines. I have sealed all the joints in my chimney, around all the door seals and cover plates. Most of the time I have no issue with smoke or smell. But once in a while this puffing happens, and it can occasionally fill the boiler room with smoke. As you know, this smell tends to linger and get absorbed into everything, so now my whole garage smells like smoke. I think if I could get the puffing to stop, I would have no issues with smoke or smell at all.

Any suggestions? I know what is happening; wood gas is building up in the upper chamber and then igniting suddenly, causing a burst of pressure that cannot all move down through the nozzle, so it blows back past the flapper on the draft fan. How do I correct this?

 

[Eric Johnson]

I've noticed that, too, and I'm sure somebody has a good solution all worked out. My boiler is in an outbuilding, so I really don't care, as it only lasts for a short time.

One thing I did notice the other day was that if your nozzle (or nozzles) is clogged, the gas can't get through it fast enough and you get excessive gas buildup in the firebox, which has to go somewhere. Maybe cracking the bypass damper for a minute or two will give it an alternative route out of your boiler. Of course, the best solution is to clear the nozzle, but that's not always possible--especially after you've filled it with wood. I make an effort every time I load to pull the tool across my nozzles and leave them relatively open before loading wood.

 

[DMX_512]

a little off-topic but...
Eric, where is your storage located...or where are you going to locate it??
Thanks

 

[Eric Johnson]

I have a concrete cistern in my basement that's been insulated with 2" foam and lined with an EPDM liner. I have a homemade copper two-stage heat exchanger that goes into the tank. I haven't gotten around to hooking it all up. Part of it is that boiler works so well without the storage in my situation and I'm not all that motivated to finish it. The other side of the equation is that I'm afraid it won't work, so I keep putting it off. Talk to my shrink.

 

[DMX_512]

I hear ya,
I now want to put my EKO 40 outside, just outside of my walk-out basement door, and am wondering about where to put the storage.
Still leaning towards keeping it inside.
My wife is like " just get started already"

 

[stee6043]

The only time I've had the "puffing" is with a cold flue. I have to believe it has to do with the clogged nozzle mentioned above???

 

[Eric Johnson]

I hear ya,
I now want to put my EKO 40 outside, just outside of my walk-out basement door, and am wondering about where to put the storage.
Still leaning towards keeping it inside.
My wife is like " just get started already"

Definitely put it inside. There, any heat "loss" is not really lost. Outside, it is.

 

[Dave T]

I learned a little trick from this site,do everything the same but when you go to close the bypass damper close it kinda slowly and wait when you get to just barally open and allow those gasses to escape before closing the damper and routing them down through the nozzles,I still close it firmly at the end..This helps if you are primalry puffing right after loading..Good luck Dave

 

[Duetech]

For cleaning the nozzle with a load on the coals I use a 3/16" steel rod about 3' long in a kind of "C" shape so I can get one end up in the nozzle. At one end is a 90 degree bend perpendicular to the "C" for a handle. One of the things I do to reduce the puffing is turn the boiler control on with the damper open before I close the top door. After a few seconds I close the damper then check the secondary flame. If the nozzle looks clear I button it up and I'm out of there other wise I use my bent rod nozzle tool and clear the nozzle the best I can. It usually only takes a couple of pokes.

 

[Medman]

It doesn't happen right after loading, but about 3-4 minutes after, even with good gasification and good draft in the flue, and flue is hot. It can continue to puff periodically for an hour or more. It's almost as if too much woodgas is accumulating in the primary and cannot get through the nozzle, but I have good flame through the nozzle too.
This weekend I plan to let the fire go out so I can clean the flue and I will check to see if the hx tubes are restricted. Even with the turbulators I wonder of the hx has an ash buildup causing backpressure? I will pay more attention to the nozzle being clean as well.

 

[Nofossil]

I've been chasing this problem myself, hoping for a definitive answer. It certainly seems to be a problem only on cold start. I think it correlates with fuel that can generate a lot of wood gas quickly - small pieces, really dry softwood, too much paper and kindling.

I'm not totally clear on the best way to stop it once it starts. It's never been anywhere near as dramatic for me as some folks are reporting, but I can sometimes get a little puff of smoke out the fan and/or out the stovepipe joints. By the way - my stovepipe joints are not sealed at all, and some are bad enough to clearly see flames during damper-open startup.

There's a related phenomenon that's actually a bit more of a problem for me. Also on startup, I'll often get a resonance that I believe starts as a series of mini-puffs at the nozzle, but creates a low frequency vibration that involves the boiler and the chimney. Opening the chimney cleanout will reduce it, and it goes away in a few seconds of running the EKO fan. Still, it can be louder than I like - sort of like a giant organ pipe.

Safety warning: You can cause a really dramatic explosion by opening the damper with the fan running. If the primary chamber is full of explosive wood gas, allowing it to mix with the flue gas (which has plenty of oxygen due to the excess air introduced in the secondary nozzle) can touch off a dramatic example of the amount of energy available in wood gas. Do not try this at home.

 

[pybyr]

I'll often get a resonance that I believe starts as a series of mini-puffs at the nozzle, but creates a low frequency vibration that involves the boiler and the chimney. Opening the chimney cleanout will reduce it, and it goes away in a few seconds of running the EKO fan. Still, it can be louder than I like - sort of like a giant organ pipe.

I've gotten that lately, especially with my experiments with chunk kindling (which seems like a very promising effort, subject to more experiments).

Sort of reminds me of the sound of an LP "pulse furnace" someone I know once had, only a lot more intense. Or like a giant hot-rod diesel truck going down the road past my house. Or makes me wonder about the WWII "buzzbomb" rockets. It's even made me wonder whether there's some potential with that phenomenon, as with the LP pulse furnaces, to extract more heat from the wood gas.

Mostly, though, it makes me realize, "whoa" - time to kick into gasification, before it gets louder!