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 Mobile View HEATING SYSTEMS ANTI SCALD VALVES BOILERS, HEATING BOILER OPERATION DETAILS BOILER CONTROLS & SWITCHES Air Bleeder Valves Aquastat Functions BOILER LEAKS CORROSION STAINS BOILER OPERATING PROBLEMS BOILER PARTS LIST Cad Cell Relay Switch Flame Sensors Circulator Pumps & Relays Expansion Tanks Gauges on Heating Equipment Limit Switches, Boilers Low Water Cutoff Valves, Boilers Mixing Valves Relief Valves - TP Valves Spill Switches Stack Relay Switch WATER HEATERS ZONE VALVES CARBON MONOXIDE/DIOXIDE CARBON MONOXIDE WARNING CHIMNEY INSPECTIONS CHIMNEYS & Flues - Asbestos Transite Pipe DRAFT HOODS - gas fired DRAFT REGULATORS - barometric dampers DUCT SYSTEMS DUCT INSULATION, Asbestos Paper DUCTS, Asbestos Transite Pipe DUST FROM HVAC? ELECTRICAL POWER SWITCH FOR HEAT FURNACES, HEATING DUCT SYSTEM DEFECTS FAN LIMIT SWITCH FURNACE CONTROLS & SWITCHES FURNACE OPERATION DETAILS HEAT EXCHANGER LEAKS STACK RELAY SWITCHES GAS PIPING, VALVES, CONTROLS GAUGES ON HEATING EQUIPMENT HEAT LOSS INDICATORS HEATING COST SAVINGS HEATING LOSS DIAGNOSIS-BOILERS HEATING LOSS DIAGNOSIS-FURNACES HEATING OIL CLOUD WAX GEL POINT HEATING OIL SLUDGE HEATING SYSTEM INSPECTION DIAGNOSIS REPAIR HEATING INSPECTION CONCEPTS HEATING INSPECTION PROCEDURE HOT WATER HEATERS HOT WATER IMPROVEMENT INSULATION MIXING VALVES NO HEAT - BOILER / FURNACE DIAGNOSIS OIL BURNERS OIL BURNER NOISE SMOKE ODORS OIL FUEL TYPES & CHARACTERISTICS OIL TANK LEAKS OIL TANK SLUDGE OIL TANKS, BURIED PLASTIC HEATER VENT RADIANT HEAT Floor Mistakes to Avoid RELIEF VALVES - TP Valves Safety Recalls BLUERAY Recall CHIMNEYS & Flues - Asbestos Transite Goodman HTPV RECALL Lennox WARNING Weil McLain RECALL SAFETY DURING HEATING INSPECTION SPILL SWITCHES - Flue Gas Detection STAIN DIAGNOSIS on Indoor Surfaces STEAM HEATING SYSTEMS Cad Cell Relay Switch Flame Sensors Mixing Valves Relief Valves - TP Valves Sight Glass, Steam Boiler Pressure Switch, Steam Boiler Spill Switches Stack Relay Switch Steam Vents LOW WATER CUTOFF CONTROLS WATER FEEDER VALVES, STEAM TANKLESS COILS Tankless Coil Leaks THERMAL TRACKING THERMOSTATS Transite Pipe Chimneys & Flues WATER HEATERS ZONE VALVES More Information InspectAPedia TM Home & Site Map Air Conditioning InspectAPedia Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Bias Pledge Contact Us |
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Barometric dampers are devices used to regulate the draft on oil-fired heating equipment such as furnaces, boilers, or water heaters. On oil fired equipment the barometric damper, or draft regulator is typically a round Tee inserted in the flue vent connector between the heating appliance and the chimney. The face of the tee contains a round "door" with an adjustable weight. The service technician adjusts the weight to control the swing or opening of this door which in turn controls the amount of excess air that can enter the flue and chimney when the oil burner is operating. The barometric damper or draft regulating device we are discussing here is normally used only on oil-fired heating equipment, not on gas-fired equipment. The equivalent draft control on gas fired heating systems is discussed at Furnace Draft Hood on gas fired equipment. |
During oil burner operation, air moves into the oil burner and combustion chamber (as combustion air) and continues onwards as combustion gases moving out of the combustion chamber, up through the boiler or furnace heat exchanger and on to the chimney where these gases are vented outside. The force with which this air or combustion gas moves is the "draft" inside of the heating appliance.
Normally we measure draft at two locations: "over the fire" or in the combustion chamber where typically we may see -0.02" of water column pressure, and "in the breech" or at the stack pipe (properly, the "flue vent connector") measured just a few inches above the boiler or furnace top, and before the barometric damper itself.
In the breech we want to see about -0.5" WC pressure. If the breech draft is too low the combustion process and venting process may be inadequate, and if the draft measured in the breech is lower than the draft measured over the fire, the oil burner and combustion chamber are operating under pressure - which is often a problem on residential heating systems since few of them are designed to work this way.
But the "draft" that the oil burner and furnace or boiler experience are not constant. For example wind blowing over a chimney top can increase draft, as can a second appliance using the same chimney as the heater. Since the force of draft is not normally constant, and since we want the draft to be constant for optimum oil burner operation, the barometric damper is installed.
The service technician adjusts the barometric damper to maintain a continuous draft in the range we described above. Then if local conditions change, the barometric damper can open or close to let in more or less additional air into the flue and chimney, keeping the draft constant.
Heating costs can be reduced by any measure that makes sure that as much as possible of the warmth produced by burning a heating fuel (such as natural gas) is sent into the occupied space rather than lost elsewhere.
An automatic vent damper, such as illustrated in Carson Dunlop's sketch here, reduces heat loss in buildings where gas-fired heaters are installed. When the heater is off the electric motor turns the vent damper to the "closed" position so that heat is not lost from the boiler nor the building by natural convection.
When the heater is about to turn on, before the burner is ignited the automatic vent damper motor opens the vent so that combustion gases can flow freely through the flue vent connector and out of the building's chimney.
Draft inducers are special fans that are installed in the flue vent connector (or sometimes in the chimney) used to vent a heating boiler or furnace. Most often we see these installed on oil-fired systems at which the technician was unable to obtain sufficient natural draft for proper oil burner operation.
If an oil burner lacks adequate draft, as we discussed above, it will not operate properly, leading to soot clogging, more costly heating bills, back pressure in the combustion chamber, and possibly unsafe heater operation.
We've installed draft inducer fans in a few cases where the building chimney design was just too difficult to get good venting by natural draft. For example a long horizontal chimney run through masonry placed a boiler too far from the vertical chimney flue for good draft. But in general, before installing a draft inducer we should make sure that the chimney is safe, not blocked, and that the heating equipment has been properly serviced and adjusted.
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