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AFUE DEFINITION, RATINGS
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CARBON DIOXIDE - CO2
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CHIMNEY INSPECTION DIAGNOSIS REPAIR
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COMPLETE COMBUSTION, Stoichiometric
CREOSOTE FIRE HAZARDS
DEFINITION of HEATING & COOLING TERMS
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
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DIRECT VENTS / SIDE WALL VENTS
DRAFT HOODS - gas fired
DRAFT MEASUREMENT, CHIMNEYS & FLUES
DRAFT REGULATORS, DAMPERS, BOOSTERS
FIRE SAFETY CONTROLS
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FLUE VENT CONNECTORS
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FUEL UNIT, HEATING OIL PUMPS
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GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
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HEATING OIL PIPING TROUBLES
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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
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ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS FROM HEATING SYSTEMS
OIL BURNER FUEL UNIT
OIL BURNER INSPECTION & REPAIR
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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
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Reset Switch - Heater Primary Control
Reset Switch Broken - Quick RepaiR
RESET SWITCH - ELECTRIC MOTOR
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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
This article discusses the use of induced-draft equipment. We provide a draft inducer fan guide: Here we explain Draft Inducers or Draft Booster Fans installed on oil fired heating equipment. We describe why you might need a draft inducer, how they work, and how a draft inducer is installed. We provider questions & answers about troubleshooting heating equipment draft, chimneys & flues, & draft inducers.
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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.
Details about draft control on oil fired heating systems (such as the oil fired heater shown in the photo above), including furnaces or boilers, are discussed right here at Draft Regulators barometric dampers on oil fired equipment. (Details about draft control for gas fired heating systems, including furnaces or boilers, are discussed at Furnace Draft Hood on gas fired equipment. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Our sketch at above left, courtesy of Carson Dunlop, illustrates the three types of draft that may be found at chimneys and heating appliances: natural draft, induced draft by a fan blowing up a chimney, and forced draft by a fan blowing combustion air into a burner assembly.
[Click to enlarge any image]
This article discusses the use of induced-draft 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.
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 it will not operate properly, leading to soot clogging, more costly heating bills, back pressure in the combustion chamber, and possibly unsafe heater operation.
The draft inducer fan shown in our photo was found in our garage of left-over stock from our heating service days. This model, the Tjernlund DJ-3 Draft Inducer Fan is sold by Tjernlund in St. Paul, MN, and the photo shows the essential parts of this draft inducer:
The draft inducer fan motor and wiring need to be adequately protected from the heat of the oil burner combustion gases, that's why you wouldn't try to make one of these at home out of an old computer fan or stereo system fan.
When is it not appropriate to install a draft inducer fan?
Be careful; it would be a mistake and possibly dangerous to install a draft inducing fan to boost oil burner draft to solve a venting or backpressure problem before the cause of that problem is accurately diagnosed.
For example, if the oil fired appliance draft is poor because the chimney is blocked, or because the appliance itself is blocked with soot and debris, or because there is inadequate combustion air, the draft inducer fan might make the problem seem to go away, but at the risk of creating unsafe conditions in the heating system.
In our photo of an oil fired heating boiler has a draft inducer fan installed. The draft boosting fan is that mechanism you see on the under-side of the flue vent connector to the left of the boiler.
If this boiler is venting into a chimney that is really right at the wall where the flue vent connector enters the block wall, it's a very short flue run and we would not expect a draft problem. Something must be seriously wrong with the boiler or with chimney itself to have induced the technician to install a draft inducer fan on this heating system.
When Might We Need to Install a Draft-boosting Draft Inducer Fan?
But where the flue vent connector run-length is abnormally long or tortuous it may be difficult to get good draft, or where the chimney size itself (to which the flue vent connector joins) is too big or too small, the use of a draft inducer might be permitted. Check with the fan manufacturer and a qualified HVAC service technician before asking that one of these fans be installed.
In the photo shown here we have a long metal flue run - we cannot see the end of it, and the flue is shared, and there is no barometric damper installed - we suspect there is poor draft at this installation.
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 we encountered a 12' long horizontal chimney run through masonry placing the 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 first.
At the chimney cleanout shown here we see a bit of debris that has collected at the bottom - which could be normal depending on what flue is being served and how long since the chimney was cleaned.
But if leave this door open not only do you nearly eliminate the chimney draft needed by the heating equipment, you are also creating a fire hazard, a fire spread between floors hazard, and a possible point of release of combustion gases into the building.
Close the little door.
How is a draft inducer fan installed?
A rectangular opening is cut into the metal flue pipe at a suitable location - usually close to the heating equipment since that makes wiring easier. The draft inducing fan comes with a paper template showing the size of the opening to cut.
The fan is mounted to the opening on the metal chimney or flue pipe so that its blades project into the flue, and so that when the fan motor runs it's pushing exhaust air away from the heating equipment and towards the chimney.
We've seen people install these fans in fireplace chimney flues in an effort to improve a fireplace that has inadequate draft, but we can't say if the manufacturer would approve that installation. There may be hazards due to creosote and other deposits from a wood-burning fireplace when one of these fans is used.
A note from Tjernlund informs us that draft inducer fan model DJ-2 has been replaced by Model DJ-3 and that all references in instructions to DJ-2 fans apply to DJ-3 models too.
Frequently Asked Questions (FAQs) about draft inducer fans for heating equipment
Questions & answers or comments about bad draft on heating equipment & the use of draft inducer fans
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