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barometric dampers

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Many years ago we used a thing called a barometric damper (sometimes called a dump damper, or pressure relief damper) in the chimney of a wood stove. The barometric damper does not respond to temperatures, rather to the strength of the chimney draft, automatically adjusting as needed to keep the draft even.

Is anyone using one of these now and how does it work for you?

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Dunno about on a forge, but on a modern wood stove several manufacturers recommend not having a chimney damper of any kind because the EPA certified stoves can adjust draft through the intake damper. EPA stoves are supposed to be "air tight" at operating temperatures. Also on a wood stove a barometric damper will encourage a creosote (chimney) fire instead of allowing you to starve it of air and possibly extinguishing it without dousing the chimney with water.

From what I have read barometric dampers were originally intended for oil fired appliances, historically very sensitive to both intake and exhaust pressure. The damper can be adjusted by moving the balance weight till a suitable pressure difference is maintained, usually measured in inches of water column. I understand that the new oil fired appliances are much less sensitive to pressure differences.


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That was my understanding of the barometric damper operation.

I am playing with the wood stove in the shop trying to encourage it to be more efficient. You know the drill, clean the chimney, dry seasoned wood, small HOT fires, keep the door closed and the stove air tight so the controlled air intake is the only source of oxygen, etc. Controlling the chimney draft was one of the last adjustments in the present system.

I can see the reasoning both for and against a damper. It was the manual damper vs automatic damper vs no damper that was under consideration. Thanks for the information.

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If you replace the old stove with an EPA certified stove you will also use much less wood to get the same heat. Just be careful when shopping if you choose to replace because many smaller stoves are "exempt." This puts budget certified stoves starting new at about $800. If you are in a pollution control region there may be programs, rebates, grants, and tax advantages to replacing with an EPA certified stove too.

check out Welcome to The Wood Heat Organization Inc.


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This is a home built stove that currently produces very little to no smoke when in use. I am trying to get maximum efficiency from the current set up before modifications are made. A stick of wood only has so many BTU's to start with, some of which must be sent up the chimney to get rid of the byproducts of combustion, but hopefully a trick or two can squeeze a little more heat out of the system.

Yes, I realize that it would be easier to just add another log to the fire, instead of spending all this time chasing and squeezing the last BTU available from the stove, but what is the fun in doing that?

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Firewood contains 13.5 to 27.7 million BTU's per cord (only 70% of those BTU's being recoverable in a stove).
Wood Pellets 6,000,000 Btu/ton
Lignite Coal 7,400,000 Btu/ton
Oil 134,000 Btu/gal
Electricity 3,413 Btu/kWh
Natural Gas 1,000 Btu/ft3
Propane 91,800 Btu/gal

#1 fuel oil has about 125,000 BTU’s in a gallon
# 2 fuel oil has about 138,500 BTU’s in a gallon
LP (propane) gas has 95,000 BTU’s in a gallon
Corn at 44,800 BTU/bushel
Bituminous coal is 11,500-13,000 Btu/lb (13k is 26 MBTU's per ton)
Blacksmithing Metallurgical coal from 13,000 Btu/lb to 15,000 Btu/lb

Standand Fireplace up to 10% efficiency
Fireplace with metal liners or tube grates up to 20% efficiency
Simple updraft stove Franklin type up to 30% efficiency
Airtight stoves up to 60% efficiency
A gas or oil furnace less than 15 years old, connected to a chimney, is about 80% efficient.
A condensing gas furnace, with two or three-inch plastic pipe vents and forced draft fan is about 90% efficient.


1 kilowatt-hour of electricity ... 3,413 Btu
1 cubic foot of natural gas ... 1,008 to 1,034 Btu
1 therm of natural gas ... 100,000 Btu
1 gallon of liquefied petroleum gas(LPG) ... 95,475 Btu
1 gallon of crude oil ... 138,095 Btu
1 barrel of crude oil ... 5,800,000 Btu
1 gallon of kerosene or light distillate oil ... 135,000 Btu
1 gallon middle distillate or diesel fuel oil ... 138,690 Btu
1 gallon residential fuel oil ... 149,690 Btu
1 gallon of gasoline ... 125,000 Btu
1 gallon of ethanol ... 84,400 Btu
1 gallon of methanol ... 62,800 Btu
1 gallon gasohol (10% ethanol, 90% gasoline) ... 120,900 Btu
1 pound of coal ... 8,100-13,000 Btu
1 ton of coal ... 16,200,00-26,000,000 Btu
1 ton of coke ... 26,000,000 Btu
1 ton of wood ... 9,000,00-17,000,000 Btu
1 standard cord of wood ... 18,000,000-24,000,000 Btu
1 face cord of wood ... 6,000,000-8,000,000 Btu
1 pound low pressure steam
(recoverable heat) ... 1,000 Btu

Just some numbers to play with.

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