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AIR CONDITIONING & HEAT PUMP SYSTEMS
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BANGING HEATING PIPES RADIATORS
BLOWER FAN OPERATION & TESTING
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BTU USAGE MONITORS
CARBON MONOXIDE - CO
CIRCULATOR PUMPS & RELAYS
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECT VENTS / SIDE WALL VENTS
DRAFT HOOD, GAS HEATER
DRAFT REGULATOR, DAMPER, BOOSTER
DUCT SYSTEM & DUCT DEFECTS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
FAN, AIR HANDLER BLOWER UNIT
FLOODED HEATING EQUIPMENT REPAIR
FLUE SIZE SPECIFICATIONS
GAS BURNER FLAME & NOISE DEFECTS
GAS PIPING, VALVES, CONTROLS
GEOTHERMAL HEATING SYSTEMS
HEAT PUMPS, DIAGNOSIS, REPAIR
HEATING COST SAVINGS METHODS
HEATING OIL PIPING TROUBLES
HEATING OIL TANKS
HEATING SYSTEM NOISES
HEATING SYSTEM TYPES
GAS LP & NATURAL GAS SAFETY HAZARDS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
MOTOR OVERLOAD RESET SWITCH
NOISE, HEATING SYSTEMS
ODORS FROM HEATING SYSTEMS
OIL FILTERS on HEATING EQUIPMENT
OIL FILL PIPE LEAKS
OIL SPILL CLEANUP / PREVENTION
PLASTIC PLEXVENT ULTRAVENT RECALL
PUFFBACKS, OIL BURNER
RELIEF VALVE LEAKS
RESET SWITCH, HEATER PRIMARY CONTROL
RESET SWITCH, ELECTRIC MOTOR
RESET SWITCH, STACK RELAY
SAFETY, HEATING INSPECTION
SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOLAR HEATING SYSTEM DESIGNS
SOOT on OIL FIRED HEATING EQUIPMENT
STEAM HEATING SYSTEMS
THERMOSTATS, HEATING / COOLING
VIDEO GUIDES: HEATING SYSTEMS
WINTERIZE A BUILDING
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
ZONE VALVES, HEATING
Draft regulation for gas fired heating equipment: draft hoods.
Here we explain the purpose and function of draft hoods or vents on gas fired boilers, furnaces, water heaters or other gas fired heating equipment. This article explains the purpose of these key venting devices on gas fired appliances.
We list and give photo-examples of common operating and safety defects found at draft hoods and draft regulators on gas fired heating equipment.
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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. If your heater is oil-fired or you are using a wood or coal stove, see DRAFT REGULATOR, DAMPER, BOOSTER for draft regulation and barometric dampers on oil fired heating equipment.
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.)
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.
These photos show an unusual accumulation of debris at a gas fired furnace draft hood opening.
Rust at this location at a furnace draft hood 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.
Soot at the Draft Hood or Elsewhere on Gas Fired Heating Equipment
Watch out: the presence of fragments of soot or soot staining on gas fired heating equipment may indicate a very dangerous condition in which improper combustion, probably inadequate combustion air or a blocked chimey or flue, can cause the production of fatal carbon monoxide gas in the building.
The safest step if you see soot formation at gas fired heating equipment is to turn it off immediately.
In all events be sure that you have working carbon monoxide detectors properly installed and located in the building as well, of course, as smoke detectors and alarms.
Stains or Debris at the Gas Hood
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.
Unsafe 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.
Watch out: This is an unsafe condition
that needs investigation and repair.
Dangerous Blockages at a water heater draft hood
Watch out: Look for signs of debris or any other material that blocks clear flow of air into the gas heater's draft hood. Blockage can cause improper venting, improper combustion, and even an increase in heating costs.
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.
This article series answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects.
The articles at this website describe the basic components of a home heating system, how to find the rated heating capacity of an heating system by examining various data tags and components, how to recognize common heating system operating or safety defects, and how to save money on home heating costs. We include product safety recall and other heating system hazards.
Continue reading at DRAFT MEASUREMENT, CHIMNEYS & FLUES or select a topic from the More Reading links shown below.
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