Boiler <-> Flue connection issues

[Carter172]

First off thank you for any assistance, I inherited this wood boiler setup upon moving to Idaho and my goal is to get it solid and reliable and eliminate the finicky issues and smoke-out.
I have a wood fired boiler with about 15 2" x three feet long fire tubes before the smoke exhausts out the stack. The fire box is approximately 30 gallons in size. The boiler has a constant draft fan supplying air. The air pushes past a damper that has an attached weight that closes when the fan shuts off.
The boiler has a straight 8" single pipe coming out the back of the unit. There was a 30 degree bend selkirk metalbestos pipe simply slid onto the top of this pipe. The flue continued about 9 vertical feet of connected metalbestos pipe out the roof. Some of the seams were taped but I noticed two 30 degree sections upon disassembly have deteriorated and need replacing.
My first problem is that if the fire got too hot, adding a couple pine logs or too much larch bark or too much wood in general, the damper prior to the firebox would start flapping wildly and the seams of the flue pipe would smoke out the attic. This leads to my second problem that I can't fill the fire box as much as I'd like so I end up feeding it once an hour or so and this will gain about ten degrees water temp on the boiler per hour.
I'm figuring I need a 258240 adapter to properly connect the boiler to the selkirk pipe. I'm also intending to replace the corroding 30's and seal every joint with silicone and tape as I work my way back up the chimney. I was concerned that I would need a positive pressure pipe such as ICC Vip+ but upon contacting ICC they said their pipe is not certified for solid fuel. Upon further research I became optimistic that simply reassembling new pipe with the proper adapter would be a permanent solution.
So this is my first experience with a boiler and flue pipe and I would very much appreciate any feedback if my plan is solid or if I'm overlooking anything and I will need to run on propane backup all winter(not ideal). The Selkirk does not list positive pressure and that was my main concern although I don't think I'm dealing with much pressure at all.
Thanks a bunch

 

[TCaldwell]

The puffing is a relatively common occurrence caused by too little combustion air provided. Since your combustion air is fixed, modifying your wood load is the only variable to reduce the puffing/pipe sealing issue.
This will take some trial and error, but generally reducing wood surface area by increasing split size or rounds, seasoned but not exceptionally dry and no bark or small scrap wood will help, maybe a wood moisture meter as well

 

[maple1]

Only 9 feet of chimney? Sounds like you don't have enough draft. A flue pipe/chimney setup should not be under positive pressure to start with - you most likely need to go higher. Plus what TCaldwell said.

 

[leon]

Who made this boiler???

Can you take some pictures of the firebox interior?


You definitely need to purchase a 2 inch boiler brush from Mcmastercarr and the connecting rods for the brush as you obviously have buildup creosote buildup that has to be cleaned out.

If you call Rockford Chimney Supply they can help you with this and ship you the right pipe and chimney cap.

The other issue is that you need to fill the firebox with firebrick to make the fire burn hotter to incinerate the creosote and keep the boiler hotter longer.


So:

1. rockford chimney supply for flue pipe and chimney cap

2. Mcmaster Carr for 2 inch boiler brush and boiler brush rods

3. full firebrick for firebox to keep the fire hot

 

[maple1]

The other issue is that you need to fill the firebox with firebrick to make the fire burn hotter to incinerate the creosote and keep the boiler hotter longer.

I don't think you could say that is needed, without even knowing what he's got for a boiler.

 

[Carter172]

The boiler was manufactured by a company in Sandpoint called Swhift. They no longer do boilers, only stainless fabrication. I have a 2 inch forstner drill bit attached to quick connect rod extensions that I use to clean the tubes. I can climb in the fire box no problem with room to work the drill and bits. I have found creosote buildup to be pretty minimal and I think the fan contributes to a pretty complete burn.
The pictures don't show the complete fire box as it's still full of wood from last year's final fire. It is a cylindrical chamber with a cone shaped bottom. The air is blown through a tube going straight down the front of the box to the bottom of the cone and also from the two outlets in the right of the picture of the fire box.
I added a 4 foot section of pipe to the top of the chimney when we moved in thinking it might help with the smoke that comes out the load door when I add wood. It still smokes into the room when feeding the boiler. I was under the possibly mistaken impression that because the unit has a fan feeding combustion air that the draft was not as important on the back end.
So the puffing is a result of lack of combustion air, good to know.
I was not aware of fire brick and I'm not sure what the best placement would be if it would help. I'm pretty sure the entire burn box is surrounded by water so would I layer the bottom cone and a little up the walls or would that effect heat transfer to the water?
I also just want to be sure that the selkirk pipe I'm working with is correct for my application. On reflection it doesn't seem like the system could be under hardly any pressure, the fan is pretty tepid, I had originally thought it was because of the puffing and smoking.
thanks

 

[maple1]

We still don't know all about your chimney either. I am still suspecting inadequate draft. Your chimney should be a draft inducer.

Your operating procedures could need refined also. If you try reloading in the middle of a burn or while there is still a fair amount of fuel in there, it can be almost impossible to avoid smoke spillage even with draft right at spec.

Some boilers have a smoke curtain to limit spillage - a flap that hangs down at the top of the door just inside the firebox. My old one did. Not sure you can add one though? As soon as you open that big door you are killing the draft your firebox is feeling from the chimney.

But first thing would be to make sure you have enough draft. A manometer works for that, I have a Dwyer that I am forgetting the model number for right now. But there were some for sale in the classified section once upon a time.

 

[leon]

You need 2 inch boiler tube brushes not drill bits.

The only thing you can do right now is lay down a couple layers of fire brick on the floor of the boiler andand stack firebrick with the narrow ends facing out on the sides and the back of the boiler to just below the fire tubes.
Place the firebrick on the bottom first and then build the back wall of firebrick first and then stack the firebrick on the sides.
You also need to remove the squirrel cage fan, soak it in dawn dish soap several times to break the grip of the dust that has collected there due to the electrostatic charge buildup and also use a steel brush to clean the air paddles of the blower. Until you do this you will continue to have issues.
In my case I bought a piece of scrap 12 by 12 by 2 inch channel iron to set on the shaker grate frame and then I just filled the firebox half full of full fire brick leaving a 12 by 12 by 36 high combustion chamber and I wish I had done this when I bough the boiler in 1983.
I would place a layer or two of standard firebrick on the floor of the boiler and then stack firebrick on the side with the narrow edge of the fire brick facing inward creating a thick wall on both sides and the end of the combustion chamber.
You will save fuel, protect the boiler walls from cavitation corrosion and the fire will burn hotter and you will have less smoke.