Barometric Damper

[sparke]

Is it OK to put a barometric damper on a wood/coal burning boiler? I have an overdraft. I measured it at .07 -.10. I was told by a hearth dealer .05 -.07 is optimal.
I am leery of a barometric because I burn 95% wood and only 5% coal. Any ideas?

 

[laynes69]

I have one on my wood furnace. I have noticed that it helps me. We have a 35 foot masonary chimney that was pushing alot of heat out the chimney. We now get even hotter burns.I do believe that is important to have then at the chimney and not at the collar on the furnace. That way the flue stays hot.

 

[Bartman]

I've had one on my boiler for 20+ yrs, it seems to be okay, although if I had a chimney fire that's the last thing I would want in my flue.

 

[jebatty]

It should be OK but keep in mind that it operates by drawing additional air into the stack. Where ever it is located, there needs to be adequate additional air supply. If it is draws air from a heated environment, then heated air will be going up the chimney and total boiler efficiency will go down. The comments by others are well-taken.

Be sure you check other ways to reduce the draft. Does your boiler have a forced air draft fan? Can you damper that air input?

 

[Bartman]

It should be OK but keep in mind that it operates by drawing additional air into the stack. Where ever it is located, there needs to be adequate additional air supply. If it is draws air from a heated environment, then heated air will be going up the chimney and total boiler efficiency will go down. The comments by others are well-taken.

Be sure you check other ways to reduce the draft. Does your boiler have a forced air draft fan? Can you damper that air input?

I always thought that you had to have a draft regulator in a flue, that if you shut down combustion air, any draft needed to naturally go up the chimney would then pull from the regulator and not through the heating appliance. Can I remove my draft regulator from my wood boiler? If so, what are the drawbacks?

 

[jebatty]

Never thought of this from that perspective. Both my woodstove and wood boiler have draft regulators, but neither one can be shut down completely, that is, at least a small amount of air still will be drawn through the appliance. I am not aware of any recommendation to have another air source for the chimney, unless really needed to control excessive draft. Note the other comment on chimney fire risk with a barometric damper. The higher the draft, the more air is admitted into the chimney, and with a chimney fire, the barom damper will send a large quantity of fresh air up the chimney and fuel the fire.

 

[Bartman]

That was my post and has been my concern, when I say "draft regulator" I mean barometric damper. Around here no one seems to know what I mean when I say barometric damper. It wasn't untill I started using this forum that I worried about the damper feeding a chimney fire, it's been on my boiler for 21+ years. From your previous post, I'm starting to wonder if I really do need a barometric damper. The one on my wood boiler is the "cheapo" Fields damper, while my oil boiler has the "good" Fields RC series, a tremendous difference in performance. Nevertheless, I have never seen a need to change the one on the wood boiler.

 

[sparke]

I ended up calling tech support at Buderus. The tech suggested a second damper instead of a Barometric. I did install a second damper and now I shut both dampers. I can't say I notice an increase in burn time but with this weather (currently -3) it is really hard to say with out a draft meter. Guess I should have borrowed the draft meter a bit longer

 

[Bartman]

I didn't even know Buderus made a wood/coal boiler..........go figure Are you saying they suggested 2 dampers on 1 flue? Which ones are used?

 

[sparke]

The boiler is probably 10-15 years old. They don't make wood boilers anymore. The unit has a factory damper at the flu exit. That damper shuts about 3/4. Yes the tech suggested a second damper in the pipe. Closing both dampers 3/4 does not seem to cause a problem. No back draft or leaking doors (new door gaskets). I will take the pipe apart in a week or two to check for creosote build up...

 

[Bartman]

Can a barometric damper be eliminated in the flue of a wood boiler?

 

[Eric Johnson]

Yes. I've never had one on any of my wood-fired boilers.

 

[Bartman]

Maybe I should remove it, I would guess you don't need it if you are varying combustion air. Since fossil fueled unit have a "fixed" burner any variations are adjusted for by the barometric damper. Does that sound right?

 

[Eric Johnson]

That sounds right to me, Bartman. I would simply say that wood boilers are not designed to be operated with a barometric damper, probably for the reason you cited.

Like Pook correctly points out, a barometric damper would tend to cool the stack temps, leading to excessive creosote formation. One possible ending to that scenario is a chimney fire, which would be very difficult to control since you would have trouble cutting off the air feeding the fire.

Sparke: To answer your original question, I'd just put in a cheap cast iron damper and play around with it. I did that for years and it worked well, particularly on very cold nights when I was trying to keep all my heat from going up the stack. You quickly get a feel for how to set it depending on conditions.

 

[sparke]

Closing both dampers 3/4 does not seem to cause a problem. No back draft or leaking doors (new door gaskets).

I already put it in a week ago
I gotta tell you. I am having a real hard time not pulling the trigger for purchase of a new boiler If it wasnt for the fact I am selling house with in 5 years, I would buy one yesterday...

 

[Bartman]

Why do you say that, are you not happy with the Buderus? Can you post pictures of it? I have wired several Buderus oil fired boilers, and would love to see a wood burner.

 

[sparke]

I am happy with the heat output and controls. I am NOT happy with burn times and amount of wood burned. I think this was a great boiler when it was made.

Here are a few pics. I usually keep the ole girl alot cleaner then this

http://s126.photobucket.com/albums/p83/sparkie68/?action=view&current=WoodBoiler002.jpg

http://s126.photobucket.com/albums/p83/sparkie68/?action=view&current=WoodBoiler001.jpg

 

[Bartman]

Your pictures didn't load, are they smaller than 350k in size? How mich is too much wood burned?

 

[sparke]

Gonna have to copy and paste in web browser...

 

[Eric Johnson]

Nice. Basically a coal burner though, I think. Take a gander at the red cast-iron wood/coal boiler on the Cozy Heat website. That's pretty similar. Craig tells me that's a coal burner that can burn wood, but is designed as a coal burner. So that might explain your wood consumption problems. But any older wood-fired boiler is going to eat a lot of wood, IME.

 

[sparke]

Well Eric, since I am sitting on 16 cord of 100% red oak. I guess shes a wood burner now I do agree the design would be more efficient coal burning. However, I don't think it burns any more wood then any old smoke dragon. Burning coal in this unit has a major learning curve. It takes a good while to learn how to tend the fire without shaker grates. I had a Memco before the Buderus and that boiler consumed even more wood. I wonder how much 1000 gallons of water storage wood help with wood consumption? I have a feeling water storage would be more convenient but not save much wood. Who knows how many BTU's are going up the chimney when the unit is idling though...

 

[Bartman]

Interesting, it looks like the old oil unit in my grandparents house that I lived in before I got married many moons ago. The unit was a National, take away the bottom door and ash pit and you have it. Does the top chamber clog up often?

 

[Eric Johnson]

My first season with a Royall 6150 I burned 21 cords of wood. It was a little gre, some of it. The next season I burned 16 cords. Then 13. There's a learning curve, I guess. I also tried burning coal, but had no luck at all. It felt good to get back to wood. I'm shooting for 10 cords with the new boiler this winter, but will probably burn more. Another learning curve, but this one won't smoke up the neighborhood.

 

[sparke]

Bart, It never clogs. I have a steel brush I run thru all the tubes at the top about once a week.

 

[Bartman]

Okay that answers my question, sort of. Call me neglectful, and I'm now ashamed to admit that I don't usually do anything until I have to. Compared to you all, I'm just a casual wood burner, the most I have burned in 1yr over the last 20yrs has been 2 cords. Usually I fire up when it's going to be real cold. Hopefully, for now, I'm going to try to modify my combustion air fan to work more like a gasifier. Since my boiler never really idles, just a lower flame, and never really goes full, I have never been too keen on keeping it going all the time. If I could get longer burns and be able to "throttle" it I would use it more often.