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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 Low Water Cutoff Valves, Boilers 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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This photo of a York gas fired furnace displays a conventional draft hood opening - the large horizontal opening space shown in the middle of the furnace. The purpose of this opening is to permit additional air to flow into the flue vent connector (stack pipe) and chimney when the gas burner is operating. This additional air flow avoids excessive draft at the gas burner. Too much draft at the gas burner could result in improper gas combustion. (The gas burner will be below this opening and behind the cover with the louvered openings. The louvers provide combustion air to the gas burner.) |
The draft hood or draft regulating device we are discussing here is normally used only on gas-fired heating equipment, not on oil-fired equipment. The equivalent draft control on oil fired heating systems is discussed at Draft Regulators barometric dampers on oil fired equipment.
Dome type gas appliance draft hood clearances:: Dome type draft hoods are commonly installed on gas fired heating boilers. For dome type draft hoods such as the funnel-shaped device shown at the center of this photo (air enters at the under-side of the dome) the manufacturer of the boiler specifies the required distance from the bottom edge of the hood to the top surface of the boiler. Usually this clearance required for gas fired appliance draft hoods is given in inches, embossed right into the lower edge of the draft hood itself. Look for the draft hood clearance specification and measure what is actually installed. If the draft hood is installed too close to the boiler top, or too high, too far above the boiler top, it will not work properly and the system may be unsafe. |
Modification or removal of a draft hood can be very dangerous, and also the presence of rust or debris on top of the boiler below the draft hood may indicate a dangerous condition such as a blocked chimney - risking dangerous combustion gas or carbon monoxide spilling in the building. We describe a case history where this occurred at DANGEROUS CHIMNEY CASE STUDY.
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These photos show an unusual accumulation of debris at a gas fired furnace draft hood opening. Rust at this location could indicate an unsafe condition. If the chimney draft is inadequate or if the chimney is blocked, or if the heater has been damaged by flooding or other wet conditions, you may observe rust and debris on and around the gas operated furnace, boiler, or water heater draft hood. Further inspection by an expert is needed.
Stains or debris at a water heater draft hood:: The black stains around the draft hood on this water heater were an indication of something seriously wrong with the installation. Tracing the flue vent connector from the draft hood atop the water heater (shown in this photo) to its connection at a chimney (not shown) we found that while the water heater was a gas fired appliance it was sharing a flue with an oil fired heating boiler whose chimney was blocked. Backpressure at the chimney was sending the oil burner's exhaust back down the gas-fired water heater's flue and into the building. |
Flue gas spillage at a water heater draft hood:: Our client is pointing to the draft hood on the gas fired water heater in the home she was buying. We could see two things: first, foam insulation on the hot water pipe was melting and second, we suspected that there was excessive flue gas spillage from this appliance. This is an unsafe condition that needs investigation and repair. |
Blockages at a water heater draft hood:: this photo of a draft hood on the gas fired water heater in the home lets us see two concerns: First, the gas fired water heater's draft hood was partly blocked with hair - so the water heater may not be burning its fuel nor venting its combustion gases safely. Second, the previous owner of the home must have kept a very hairy and shed-prone dog in the basement where it's hair was so thick in the air that the draft hood was blocked. If this home were going to be occupied by someone with dog allergies, extensive cleaning would also be in order. More photos and descriptions of gas water heater defects including draft hood issues can be seen at GAS FIRED WATER HEATERS |
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