Barometric Damper and Chimney Connector

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LeonMSPT
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Post by LeonMSPT » Sun. Jan. 18, 2009 8:03 pm

I replaced the galvanized pipe with black steel, and installed and set BDD with manometer. Nice results, but I think I will be glad I did the work with "T"s, with plugs to remove and clean the critter.

I burn wood on weekends and coal during the week. I've been burning two weeks, and there is an accumulation of about 1/8 inch of what looks like oily dust on the inside of the smokepipe above, below, and through the BDD.

Got .025 inches of draft on high fire with the combustion blower running with the adjustment knob on the BDD at the minimum. Wonder if I should clean the pipe and adjust for .03/.035... not getting any smoke back in the house right now. Once in a very great while there will be a little odor of creosote/smoke or coal smell... usually right around loading time. Not enough to worry about... CO detector rarely ever shows anything at all, and when it does I've started the ATV and drove it out to plow the yard. Never had any CO show from the wood/coal boiler at all, ever.

Used radiused "T"s , three of them, and about five inches of pipe on each end... worked perfect. Cut the fishmouth that came with the damper into one of the "T"s and it worked great. Sealed around it with boiler cement and finished the job.

I did try lighting some of the dusty looking stuff in the pipe. Seems to burn pretty good... Combination of fly ash and condensate, I think it would make a healthy and dangerous fire if allowed to accumulate to any degree.

Recommendations?

Thanks in advance...

Cousin runs a dealership and has access to stainless... thinking about redo in the spring with more rugged stainless pipe and insulating the length of it... would just make it so if there was a pipe fire, it would be less likely to hurt anything. And the heavier pipe would stay hot longer, especially if it was insulated. Although with the BDD, the air does rush through there pretty good when it's idling.

By the way... without the BDD, the chimney is pulling about 1.2 inches of draft... YIKES! Slightly more than the maximum .04 inches New Yorker recommends...

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coaledsweat
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Post by coaledsweat » Sun. Jan. 18, 2009 9:46 pm

LeonMSPT wrote:By the way... without the BDD, the chimney is pulling about 1.2 inches of draft... YIKES!
That's not a draft, it's a vacuum! :shock:

 
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rockwood
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Post by rockwood » Sun. Jan. 18, 2009 10:18 pm

I wouldn't recommend using a baro damper when burning wood because the cooler air entering the chimney at the baro will cool the flue and result in more creosote accumulation and raise the risk of chimney fires. As you mentioned, the "dusty looking stuff" will burn.
When you burn wood, you want the flue to stay hot (350 degrees or so) to limit creosote. The colder the surface of the inside of the flue the more creosote build up.
If you do continue to burn a significant amount of wood with the baro in place you should check/clean the flue very frequently.
I would just burn the coal all the time just to be safe. :)


 
LeonMSPT
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Post by LeonMSPT » Sun. Jan. 18, 2009 11:52 pm

I have been burning wood most of my life, and am new to coal. So far, I like it. But the wood is laying around, and I am here on the weekends. It's an interesting thing to watch with the BDD in place.

1. Magnetic thermometer on the door on high fire runs around 500 degrees...
2. Magnetic thermometer on the flue pipe between boiler and BDD goes up to 350/375 and hangs there until it goes back to idle.
3. Flu pipe above BDD is just maybe hot enough that you can't hold your hand on it, but significantly cooler than 350/375.
4. Smoke from chimney is lighter, and clears up nearly entirely 10 or so minutes into a burn.
5. At idle, there is minimal to no smoke at all from the chimney

Knowing that creosote will burn if you heat it much over 450/475, it appears I am remaining below the break point for ignition. Cleaning it often should mitigate any danger from this.

Without the BDD in place, which I was for a month and a half before I conjured up the image of a humungous chimney fire...

1. Door was 500 degrees, after burning for a looooong time. Bad
2. It took twice as long a burn to get the boiler up to temperature. Recovery times were half again to twice as long as now. Bad
3. Flu pipe temperatures with the same thermometer I am using now ran 475/500 degrees consistently when burning. Bad (that'll ignite creosote)
4. With 1.2 inches of "vacuum", the fire appeared "strained" the entire time... I had alot of puff backs, and a decent coal gas explosion. Bad (exciting)
5. When the boiler was lit on wood, it smoked, heavy smoke, the entire time... less at idle, but it still smoked. Bad

Now. Figuring like an ex firefighter...

1. Less heat in the flu, in fact not even near the ignition temperature for creosote. Good.
2. More heat in the boiler, leading to shorter burn times, faster recovery times, and less often reloading.. Good.
3. Products of combustion are being drawn into the chimney at a much faster velocity, and maintaining that velocity between the BDD and the chimney top. Without the BDD, stack velocity was minimal... too much draw and not enough flow. Good.
4. Everything that goes into the chimney is burned more thoroughly because I am not trying to burn in a vacuum anymore. No more strain on the fire. Good.
5. I am burning less wood and coal now, and getting more heat. Good
6. I need to monitor the condition of my flu pipe and clean it when it's dirty. (Neither good, nor bad... had to do that anyway)

It appears, I could be wrong... that with the BDD in place, I absolutely need to monitor flu pipe conditions and clean it when it's more than 1/8 inch or so deep. However, with flu temperatures being 350 degrees, unless something changes in the mix the temperatures aren't going to be there to light the creosote in the first place. If I were to have a flu pipe fire, that would be the ignition source for a chimney fire. Absent a flu pipe fire, I cannot conceive of how a chimney fire would get started in the first place. Temperatures aren't there... and the chimney is pretty clean so far this season.

Interesting too... chimney is "exposed' in the bathroom above the boiler... it's warm to the touch after a day or two of burning. Now, this is a thick chimney... 8 inches of brick outside to inside, with a 6 x 6 I.D. square stainless liner to the top. It's pretty "slick", and being sheet steel pretty easy to heat up.

Thanks for the advice and recommendations... it's on the verge of being a coal boiler only pretty soon...

 
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rockwood
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Post by rockwood » Mon. Jan. 19, 2009 12:59 am

Knowing that creosote will burn if you heat it much over 450/475, it appears I am remaining below the break point for ignition.
What you want to do is prevent/limit creosote from forming by burning hot fires with no smoldering. Prevention is key.
Let me share what happened to me.
Many years ago I was relighting a stove after the (wood) fire had smoldered and gone out during the night leaving creosote in the stove and flue that ignited when I lit the newspaper and wood, so from experience I can tell you that chimney fires can start at low temperatures with a cold stove and flue.
Let me tell you, the roar of a chimney fire is something you never forget. :shock: Luckily I was able to starve the fire for oxygen snuffing it out before any damage was done. :)
I don't know if I could have gotten the fire snuffed out if there was a big gulp of air let into the flue by a baro damper, as it would take precious time to get the baro damper closed or covered up to stop the air feeding the out of control fire.

 
LeonMSPT
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Post by LeonMSPT » Mon. Jan. 19, 2009 9:58 am

Been to a few chimney fires over the years, and only had one when I was a kid. They sound really scary, and the headlines and news coverage, and other sources make them sound horrific.

How many other chimney fires have you had when you slept through them, or weren't home?

I don't "want" a chimney fire. The potential is there to damage my house, burn it to the ground, and for people to get killed or hurt. However, a chimney fire is not the devil coming to get me because I didn't clean my chimney either. Chances are, everything's going to be okay.

Burning a wood boiler generates some smoke and creosote. I take as many steps as I can to not make any more than I need to. But it's a fact of life. I don't load unless there is a demand, and only on top of a healthy bunch of kindling wood, or a deep bed of coals. Then it burns until it's hot and goes to idle.

Open flame will often ignite creosote. It's why I rarely use much more than a single sheet of newspaper and a few sticks of kindling wood... enough to get the smaller splits to light, then progress to medium/large depending on load and burn duration...

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