I'm building a homemade boiler

[brenndatomu]

Could a dirty chimney Cause smoke with a hot burn?

Yes, but, the smoke is usually black, not blue...in my experience. Blue smoke sound like typical OWB incomplete combustion

 

[TCaldwell]

The blue smoke can happen when the batch dies down and combustion temp decreases, same as what happens when you first start a fire, will smoke till combustion temp is high enough to burn off volatiles, sometimes reducing overall airflow will help at the time.

 

[warno]

I couldn't pick out the sizzling sound you mentioned.

But some boilers will 'kettle' in certain conditions. I think it's the way water flows internally in the boiler, or more like doesn't flow in certain spots or cavities or 'dead flow' areas inside. Like eddies in a stream. I don't think I'd describe it as a sizzle, sounds sorta just like you'd imagine boiling would sound inside. Maybe reduced flow from the new pump is now highlighting these spots?

I forget - do you have a bypass loop on the boiler? If not, adding one might help. My old wood/oil unit did, it had another circ in it that would come on at a certain temp (forget the temp now). I think I was told it was there to prevent boiler shock, but it would make more flow through the boiler and maybe stop a kettling condition. If that's what's happening.

I do remember this sound being much less with the other pump running. As far as a bypass goes, I don't have one. I have been thinking about building a "system optimizer" like pro fab uses on theit systems. It should stir up the boiler water pretty well.

Thanks for the info on the smoke guys. I'll play around with my air flow alittle more to see if I get it alittle better.

 

[warno]

I have been thinking about using my existing thermomix valve and building one of these http://www.ecomfort.com/Pro-Fab-Ind...70&var1=ecomfortusa&var2=shopzilla&var3=42339

What I'm alittle confused about though is if I put a bigger pump or 2 pumps on the "line out" port, would that over power the pump feeding the optimizer manifold? Or should I just stick with my current setup?

 

[warno]

Another lesson learned today. I accidentally got a few green splits mixed in with my load I picked up yesterday. When I went to load this morning I came out to no fire and 129 temps down from 180. So I relight the fire and go back inside. After an hour straight of fan running I figured I'd go out to check what's taking so long. Water temp only made it to 145 in this time. So, I open the door to a bridged load of wood not dropping down and 2 pieces spewing sap out of the end. So I stirred things up and tossed in a few more pieces on top and went back inside. After 15 minutes the fan quit running and the stack starts smoking like crazy. I'm assuming because the sappy pieces in there still doing their thing.

So I guess a moisture meter will be in my tool box in the near future.

 

[warno]

I thought I'd post a pic of my chimney After about 6 weeks of burning.



And after dragging the brush through it once



And with the second pass

 

[GENECOP]

Looks about right, I think as long as the coating remains powdery and easily sweeps, your good...

 

[warno]

It was all crumbly grey stuff. The rope on my brush knocked a bunch of it out when I dropped it in. Hopefully with added storage and batch burning next year this will improve.

 

[warno]

I figured I'd post a not so exciting video of my smoke out put on a fresh start up.

So this is right after lighting the fire with the fan on.

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And this is about 10 minutes after start up. Alot of heat up the stack.

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I'm going to try to build a turbulator to put in my heat exchanger and I have a new fan on the way to hopefully get some air up over top of the fire as well as under it for possibly a cleaner burn.

 

[Born2burn]

Are you preheating any of your combustion air, if you try putting some secondary air in see if you can run the pipe through a hot area first before you discharge the air over the fire. Should help a lot if you can get air temps up to 250 or 300F. Might achieve a partial secondary burn when temps are up!

 

[warno]

The air is pulled from inside the boiler shed, it gets to about 100 degrees in the shed. Then the air is pushed up through the coal bed.

I can run my above fire air through my fire grate to get warmed up before exiting above the fire. My fire grate is made of 1" stainless steel pipe.

 

[warno]

So revisiting the sizzling sound, I was burning some 15-18% oak today in the boiler. The fire was really well established when I checked on it. And when I opened the door is was met with a roaring fire and all the creosote around the door frame was either bubbling up or in a liquid state. I took my ash rake and scraped the top side of the fire box and all the creosote on the top was liquid.

So I'm wondering if my sizzling sound is my creosote boiling off the walls of the firebox?

 

[GENECOP]

What is causing the creosote?. Bubbling up in a liquid state around the door frame...sounds like a strange condition to start with...In three years of burning I have encountered liquid creosote maybe twice...maybe caused by my damper closing , idling to long etc...On a full out burn, I don't think creosote should be developing....

 

[warno]

Since I'm only heating my garage this season I'm getting LONG idle times. Especially since this winter had been more like early spring from the get go. So I have been building alot of creosote. When I say it's in liquid form it was like thick wet paint under crusted over bubbles, it's doesn't run down like water but it hangs there pretty good. Around the door frame I mean on the inside of the feed door, I have about 4" of steel before the actual firebox opening. The creosote builds in that area and on the top of the firebox while at idle. When it's burning full on its not making hardly any smoke but then it goes into a long idle period.

 

[warno]

Here's some pictures of my door frame. The 2 sides and top.

This is the hinge side of the door frame, I scraped the crusty stuff off and this is the goo under it.



This is the top of frame, these are the bubbles I was referring to.



And the latch side of the frame, more bubbles and goo.

 

[hondaracer2oo4]

This is a conventional own with a cold water jacket around the firebox. The creosote is perfectly normal for this style boiler. I assuME you have a hot spot in your boiler and that's what you hear bubbling. Maybe try to increase your pump flow in the boiler to get rid of that hot spot. Hot spots are bad for the metal and can cause it to break down quickly leading to a leaky boiler.

 

[warno]

Ok I'll try that. Thanks.

 

[maple1]

Are your return temps always above 140?

 

[Fred61]

The dry crusty stuff is creosote that has started to dry out and burn. It is spaced far enough from the cold walls to get hot enough. I suspect your fire is not hot enough for the area of water jacket that is exposed to the fire, The large area is keeping the fire cold. Is there any way that you can insulate the fire from the jacket with refractory to reduce the number of square feet of surface that is exposed to the fire. I think if you could accomplish that you will see a totally different boiler in the way it burns.
At one time I had a stove that I wrapped with several feet of 3/4 inch tubing for heating water. It drastically changed the way that it burned and did exactly what you are seeing on your unit. I removed the tubing and opted for a "Hilcoil" within the firebox and even with that I could see a difference in the way it burned.

 

[warno]

Are your return temps always above 140?

Always. my delta is only about 14 degrees and the set point is at 180. And on a cold start in have a thermomix valve plumbed in the system.

The dry crusty stuff is creosote that has started to dry out and burn. It is spaced far enough from the cold walls to get hot enough. I suspect your fire is not hot enough for the area of water jacket that is exposed to the fire, The large area is keeping the fire cold. Is there any way that you can insulate the fire from the jacket with refractory to reduce the number of square feet of surface that is exposed to the fire. I think if you could accomplish that you will see a totally different boiler in the way it burns.
At one time I had a stove that I wrapped with several feet of 3/4 inch tubing for heating water. It drastically changed the way that it burned and did exactly what you are seeing on your unit. I removed the tubing and opted for a "Hilcoil" within the firebox and even with that I could see a difference in the way it burned.

Only the upper half of my fire box is surrounded by water. The lower half is full of ceramic and fire brick. My water jacket doesn't surround the whole firebox like most conventional boilers. The creosote on the top of my firebox dries up and burn off just like the door frame does. That's why I was wondering if maybe that's what I'm hearing.

I'm going to try turning my pump speed up and see if that helps things a bit. Maybe it is a hot spot in the water jacket.

 

[maple1]

Is the door frame water jacketed?

And I forget now - but where is your combustion air coming in at? Through the door?

 

[warno]

About 1 inch of the door frame has water around the top. The rest is surrounded by insulation on the outside of the boiler. This picture in build stage you can see where my water jacket meets the door frame.



And my air enters into the back, bottom, through the ash pan. It blows in the ash pan and comes up under the fire. It's the longer pipe in this pic.

 

[hondaracer2oo4]

I don't remember, did you extend your supply or return piping into the boiler at all? Certainly could e trapping some real hot water between th top of the door area and the heat exchanger.

 

[Fred61]

Creosote deposits are a result of the non combusted gasses condensing on the surfaces which, to me means there is either an abundance of those materials emenating from the fire condensing or the walls and other surfaces which are too cold and the combination of moisture and smoke is condensing.
Speeding up the pump could be the wrong way to go.

 

[warno]

The return line extends into the jacket about 3/4 of the way to the front.

I tried the pump speed but had to turn it back down anyway because it started cavitation in my heat exchangers.

Hopefully next year with my other pump running to the house it will get this thing stirred up so it doesn't have any hot spots anymore.