barometric draft regulator

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Can someone explain the purpose of this device?
I have seen one on an old oil fired boiler I used to have, and have heard it discussed occasionally with regard to wood or coal stove
use. What is its primary function and how does it work. It seems to me to be primarily a way to reduce draft and velocity at the ignition source. As draft increases the flap opens and air is drawn into the chimney from beyond the fire not at it. Does this sound right?

How is it set up? There must be allot of trial and error in the process of setting the counter weight correctly.( the one i had on the oil boiler had a screw in balance weight)

 

[Corie]

You're correct in the function of the device.

The counter balance weight you're talking about should be adjusted by the installer, using a draft meter when the unit is installed. Since coal stoves generally operate best over a small region of draft control settings, the barometric damper allows the installer to "tune" the chimney system for the stove.

For homeowners who do self installs, it defeats the purpose of the barometric damper if it not properly adjusted EXCEPT for the fact that under extreme over-fire conditions it will probably still be pulled open to slow things down, assuming it hasn't been adjusted to the point that it would take a gale blowing against the flapper to open the thing.

 

[nshif]

Try

http://www.fieldcontrols.com/draftcontrol.php

for more info. I had one on an old Fisher and took it off. Didnt think it was worth the loss of the heated room air it sucked out

 

[DeanBrown3D]

I can't understand why one would be used for wood - it would cool down the flue gases by mixing in cold air. And you can turn down the air flow at the stove or furnace instead.

 

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I burn coal and wood with no trouble without one. I remember the old oil fired boiler I used to have had the draft control scred closed with a crywall screw. My efel Harmony with a thermostatically controlled air intake system orks great.see

 

[Corie]

Many coal stove manufacturers require a barometric damper to be used and require that the draft be properly set for their desired range of operation.

 

[webbie]

Even with wood, it would even out the draft on the stove, and therefore allow it to operate within a range of better combustion. Consider a regular chimney that gets warmer and cooler at various parts of the fire, and also the outside weather and wind changing. A barometric evens this out- spoils excess draft, and therefore allows the flame and heat to stay in the stove longer.

Go back to the three T's of combustion - Time, Temp, and Turbulence. All of them are enhanced when draft is steady - the gases stay in the combustion zone longer, have the right mixtures of air/fuel, and stay hotter.

Year ago I spoke to two scientists from Corning (the first cats for stoves) and they were firmly convinced that every cat stove would ideally have a baro.

 

[johnsopi]

I have one on my Wood furnace. When the fire burning hot it is open about half way, this slow the draft down? As the fire dies the damper closes increasing the draft. Is this correct? As far setting the weights mine says @ .03 with a max of .05. But creosote
builds up on the inside of the flap from the cooler so the weight must mess up the settings. I pull the whole damper out and remove
the build up and reset it.

 

[laynes69]

I have a wood/coal furnace and I have one on mine. I get hotter temps in the firebox, a very clean burn and longer burn times. The excess draft isn't removing the extra heat anymore. As far as cleaning it, it has stayed very clean. With the draft slowed now, the heat holds in the furnace longer. Mine made a big difference.