Help! Smoke Puffing Out of Boiler

[ejhills]

Tarm Solo MB 55, A natural draft boiler.

So I was having difficulties with the boiler and high stack temps....
So a barametric draft damper BDD) came to the rescue and dropped my stack temps under control

This evening it is -4 with winds from the at 2 mph.

The box is warm at 200'f and the samson draft regulator is closed and set at 80'

Slowly, the BDD opens and then quickly closes, then the bottom draft pops open full, Smoke exits through the draft and the vent in the door!

Then the bottom draft slams shut, leaving smoke in my basement\

Barametric pressure is steady....

Help

 

[matt701]

Is this happening right after you load it or had the loading door open for awhile or just randomly?

 

[Dave T]

How long have you been firing this Tarm??Have you done any chimney sweeps??Is the chimney over the roof line 3'??
Dave

 

[ejhills]

Been Firing It since November....

First time it has been this bad

Only thing new is the BDD.

Chimney Inspected Every 2 weeks... Clear shot 40+ feet tall, a solid 8' over the roofline.

 

[LeonMSPT]

Sounds like a "puffback" that happens when you slam the air supply shut on an airtight woodstove.

Your boiler is screaming away, making heat like a mad dragon. Great air supply, cooking the wood, making plenty of gas to burn.... and with that nice air supply it burns up real nice... then all the sudden, the air supply gets cut off.

Draft pull increases on the chimney because the bottom is obstructed. The BDD opens to relieve that... it's what it does. The boiler is now "air starved"... the fire thinks it's dying, choking to death, and it pulls hard to try to survive... actually, flammable gasses that weren't burned off because the air supply was reduced suddenly, are pulled up toward the BDD... and the air from the BDD meet it somewhere in the middle... of course, very hot and flammable gasses explode when they find an air supply. "POOF!"

Smoke gets in your eyes...

Any way to change the motor mechanism around or fix it so it will shut down over a couple minutes as opposed to a few seconds? Longer arm on the actuator, smaller gear/bigger gear, step mechanism?

If the air supply wasn't chopped so suddenly, it likely would either help the problem alot or do away with it.

 

[matt701]

Thats why I was asking when it was happening. I'm not familiar with the unit, but if you have the loading door open for awhile and the fire builds up because of the increased oxygen being let in while you load, then you slam the door closed, the same thing could happen. My wood furnace was doing that and what I have been doing to eliminate that was to actually close the manual chimney damper about 3/4 and then slowly open the feed door, load, close the feed door and quickly open the damper back up. This keeps the fire from requiring so much oxygen that it doesn't get enough oxygen for the existing fire when you close the feed door. With the really really cold weather we just went through, I was reloading my stove when it was already really hot and drafting more than normal. I l would load it, close the door and the puffing started. It actually blew my cleanout cap out of the bottom of my pipe (I have it screwed together now like it should be). Just my opinion of what happened to me, may not be the same problem.

 

[LeonMSPT]

May not be the exact "same" problem, but the mechanism is roughly the same from the sounds of things... Seems like slowing down the actuator on the closing mechanism might be where the solution might lay. You could have done the same thing by just closing the door slowly, but in my own case... smoke gets in your eyes... when the door is open too long.

 

[ejhills]

Wow... great science....

Thanks

I let the fire burn down and reset the draft regulator, things are much calmer now.

I guess the lesson here might be....

Approach the fire slowly, and don't give or take too much are too fast.

 

[LeonMSPT]

Problem with fire...

Adjustments and changes take time to observe the results.
The bigger the change, the bigger the result.
You can't turn it off.
If you make a big change, don't like the result, you commonly have to "live with it" for a period of time.

 

[Dave T]

Hey guys I was noticing small puff backs after loading my EKO the problem was closing the bypass damper to quick,Thanks for the sugestions..Dave

 

[Eric Johnson]

Sounds like a "puffback" that happens when you slam the air supply shut on an airtight woodstove.

Your boiler is screaming away, making heat like a mad dragon. Great air supply, cooking the wood, making plenty of gas to burn.... and with that nice air supply it burns up real nice... then all the sudden, the air supply gets cut off.

Draft pull increases on the chimney because the bottom is obstructed. The BDD opens to relieve that... it's what it does. The boiler is now "air starved"... the fire thinks it's dying, choking to death, and it pulls hard to try to survive... actually, flammable gasses that weren't burned off because the air supply was reduced suddenly, are pulled up toward the BDD... and the air from the BDD meet it somewhere in the middle... of course, very hot and flammable gasses explode when they find an air supply. "POOF!"

Smoke gets in your eyes...

Any way to change the motor mechanism around or fix it so it will shut down over a couple minutes as opposed to a few seconds? Longer arm on the actuator, smaller gear/bigger gear, step mechanism?

If the air supply wasn't chopped so suddenly, it likely would either help the problem alot or do away with it.

Bingo!