Inspection, Tuning & Repair Guide to Heating System Oil Burners
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Oil Burners: Guide to Oil Burners for heating systems, boilers & Furnaces: basic parts, operation, maintenance, performance & money-saving tips
How oil burners work: sequence of operation, oil burner safety controls
How to inspect & repair oil burners - homeowner basics, service technician basics, diagnosis, repair
Cleaning & maintenance guide for heating systems
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Here we discuss Oil Burners: Guide to Oil Burners for heating systems, boilers & Furnaces: basic parts, operation, maintenance, performance & money-saving tips
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this website answers most questions about central heating and water heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.
Homeowner's Guide to Oil Burners for Boilers, Furnaces, & Water Heaters
Oil fired heating equipment such as hydronic (hot water) boilers, steam boilers, warm air furnaces, and water heaters, have used heating oil, usually No. 2 heating oil, and various types of oil burners to burn the fuel, thus providing a heat source for nearly 100 years. Here we describe the basics of how oil burners work, and we provide a guide to their inspection and problem diagnosis and repair.
How Oil Burners Work
Refer to the schematic of a conventional oil burner shown below, where we list the major parts parts of a modern oil burner. The sketch is courtesy of Carson Dunlop.
Sequence of steps in home heating or hot water heater oil burner operation:
Electric power on: In response to an aquastat or other heating boiler, furnace, or water heater control, electrical power to the oil burner is switched "on". (ELECTRICAL POWER SWITCH FOR HEAT)
Electricity is connected through a safety control such as the Cad Cell relay labeled "primary controller" in the sketch. Details: Aquastat, Cad Cell Relay, or Stack Relay Switch
Oil burner electric motor starts: The primary controller permits electrical power to flow to the electric motor shown on the right side of the oil burner, causing the motor shaft (not shown) to rotate. See OIL BURNER NOISE SMOKE ODORS.
Oil burner's Electric Motor shaft rotates, driving other parts through a coupling: the spinning shaft of the electric motor extends horizontally through the inside of the oil burner motor where it is coupled first to a rotating squirrel cage fan - the oil burner's air blower (providing combustion air), and second to the the air blower and oil pump (fuel unit).
High speed oil burner motors spin at 3450 RPM. Older "low speed" (and quieter) oil burners use an electric motor rotating at 1725 rpm.
Combustion air: Oil burner blower fan spins, drawing combustion air through adjustable air intake slots on the left side of the oil burner, and simultaneously,
Heating oil delivery: the electric motor shaft extension drives the oil pump (fuel unit) shown on the left-most side of the oil burner in the sketch.
The oil pump (oil burner fuel unit such as a Sunstrand™ fuel unit) draws heating oil from the oil tank through a fuel line connected to the oil tank (hopefully through an external oil filter and an internal filter screen) and pressurizes the heating oil to 100 psi or more.
Pressurized heating oil flows out of the oil pump thorough a high pressure oil line into the oil burner tube where it is converted to a fine spray by an oil nozzle attached to the end of the nozzle assembly. See OIL TANKS, OIL TANK PIPING DEFECTS
Heating oil ignition: electricity is also delivered to an ignition transformer (the black box on top of the back of the oil burner). The ignition transformer converts the incoming 120V electrical power to very high voltage which is fed to two electrodes attached to the nozzle assembly.
The oil burner nozzle electrodes, separated by a small gap, produce an electrical spark (usually continuous or "continuous ignition oil burner operation" vs. "intermittent ignition" on some older systems) which is right in the path of the oil being sprayed by the oil burner nozzle, causing the oil to ignite.
Safety controls will turn off the oil burner if flame ignition is not successful.
This feature prevents continuing pumping un-burned heating oil into the system. See Cad Cell Relay Switch Flame Sensors and Stack Relay Switch
Heating oil combustion: the sprayed, burning heating oil heats the interior of the furnace, boiler, or water heater combustion chamber which is normally lined with a material whose surface will get very hot but won't burn.
The combustion chamber liner prevents the oil burner from damaging the cast iron or steel boiler itself, while the hot surface of the combustion chamber liner helps make sure that all of the fine droplets of oil sprayed into the combustion chamber do in fact ignite.
Heat transfer: hot combustion gases from the burning heating oil flow (usually upwards) through the furnace, boiler, or water heater heat exchanger where they transfer heat to that appliance before continuing to flow through a flue vent connector (stack pipe) and then outside through a chimney. See: BOILERS, CHIMNEYS, FURNACES,STEAM HEATING,WATER HEATERS
Electric power and oil burner off: when the aquastat, thermostat, or other primary control senses that the desired temperature has been reached, electric power to the oil burner is turned off, stopping the electric motor from spinning, thus stopping the combustion air blower, oil pump, and turning off the ignition transformer. See Aquastat Functions and THERMOSTATS
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Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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More Information on Building Diagnostic Inspections and Repairs
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
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