Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
AFUE DEFINITION, RATINGS
AGE of CHIMNEYS & FIREPLACES
AGE of HEATERS, BOILERS, FURNACES
BACKDRAFTING HEATING EQUIPMENT
BOILER COMPONENTS & PARTS
BOILER CONTROLS & SWITCHES
BOILER NOISE SMOKE ODORS
BOILER OPERATING PROBLEMS
BOOKSTORE - InspectAPedia
CARBON DIOXIDE - CO2
CARBON MONOXIDE - CO
CHIMNEY INSPECTION DIAGNOSIS REPAIR
COMBUSTION AIR for TIGHT buildings
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
COMPLETE COMBUSTION, Stoichiometric
CREOSOTE FIRE HAZARDS
DEFINITION of HEATING & COOLING TERMS
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECT VENTS / SIDE WALL VENTS
DRAFT HOODS - gas fired
DRAFT MEASUREMENT, CHIMNEYS & FLUES
DRAFT REGULATORS, DAMPERS, BOOSTERS
FIRE SAFETY CONTROLS
FIREPLACES & HEARTHS
FLAME COLOR, BLUE vs YELLOW COMBUSTION
FLOODED HEATING EQUIPMENT REPAIR
FLUE SIZE SPECIFICATIONS
FLUE VENT CONNECTORS
FUEL OIL TYPES & CHARACTERISTICS
FUEL UNIT, HEATING OIL PUMPS
FURNACE CONTROLS & SWITCHES
GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEATING LOSS DIAGNOSIS-BOILERS
HEATING LOSS DIAGNOSIS-FURNACES
HEATING OIL PIPING TROUBLES
HEATING OIL TANKS
HEATING SYSTEM NOISES
HEATING SYSTEM TYPES
HIGH EFFICIENCY BOILERS/FURNACES
HOT WATER HEATERS
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
GAS LP & NATURAL GAS SAFETY HAZARDS
MANUALS & PARTS GUIDES - HVAC
Natural Gas Combustion
NO HEAT - BOILER
NO HEAT - FURNACE
NOISE, DUCT VIBRATION DAMPENERS
NOISE, HEATING SYSTEMS
NOISE, WATER HEATER
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS FROM HEATING SYSTEMS
OIL BURNER FUEL UNIT
OIL BURNER INSPECTION & REPAIR
OIL BURNER NOISE SMOKE ODORS
OIL BURNER SOOT & PUFFBACKS
OIL FILTERS on HEATING EQUIPMENT
OIL FUEL TYPES & CHARACTERISTICS
OIL HEAT FIRE SAFETY CONTROLS
OIL LINE CLOGGING FIX
OIL LINE QUICK STOP VALVES
OIL LINE SAFETY VALVES, OSVs
OIL FILL PIPE LEAKS
OIL PUMP FUEL UNIT
PLASTIC Plexvent / Ultravent RECALL
PULSE COMBUSTION HEATERS
RELIEF VALVE LEAKS
RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - STEAM TP VALVES
RELIEF VALVES - Water Heaters
Reset Switch - Heater Primary Control
Reset Switch Broken - Quick RepaiR
RESET SWITCH - ELECTRIC MOTOR
Reset Switch - Stack Relays
SAFETY, HEATING INSPECTION
SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOOT on OIL FIRED HEATING EQUIPMENT
SPILL SWITCHES - Flue Gas Detection
STACK RELAY SWITCHES
STAIN DIAGNOSIS on BUILDING INTERIORS
STEAM HEATING SYSTEMS
THERMAL EXPANSION of HOT WATER
THERMAL EXPANSION of MATERIALS
THERMAL MASS in BUILDINGS
THERMOSTATS, HEATING / COOLING
THERMOSTATS, WATER HEATER
TRANSITE PIPE CHIMNEYS & FLUES
VIDEO GUIDES: Heating System Videos
WINTERIZE A BUILDING
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
ZONE VALVES, HEATING
Here we explain Draft Hoods & Vents, providing a Guide to Draft Hoods on Gas Fired Furnaces, Boilers, Water Heaters and explaining the Purpose, Inspection, Repair of these key venting devices on gas fired appliances. Details about draft control for gas fired heating systems, including furnaces or boilers, are discussed right here at Furnace Draft Hood on gas fired equipment. (Details about draft control on oil fired heating systems are discussed at Draft Regulators barometric dampers on oil fired equipment.
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.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
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.
[Click to enlarge any image]
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.
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.
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.
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
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.
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.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References