How to diagnose loss of heat, heating boiler noises, leaks, odors, or smoke
Troubleshooting heating boiler oil or gas burners & controls
How to inspect & repair central hot water heating boilers - hydronic heating
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Here we discuss how to recognize & diagnose oil fired heating boiler noises, leaks, odors, or smoke. This website answers most questions about central hot water heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect
residential heating systems to inform home owners, buyers, and home inspectors of common heating system defects.
The articles at this website describe how to recognize common oil-fired heating appliance operating or safety defects, and how to save money on home heating costs. Also see CHIMNEY INSPECTION & REPAIR GUIDE for details of chimney inspection, diagnosis, and repair, including blocked chimney flues, chimney backdrafting, leaks, and odors from flues. Separately we discuss CARBON MONOXIDE hazards in buildings. Readers concerned with LP gas or natural gas combustion flue gas products and hazards should also see Natural Gas Combustion Products and also LP & Natural Gas Safety Hazards.
How to Diagnose Noises & Odors During Heating System & Oil Burner Operation
What Oil Fired Heating System Noises are Normal and What are the Noise Sources?
Some heating system and heating oil burner noises are considered normal. These include noises coming from the following items:(The sketch is courtesy of Carson Dunlop. )
Electric motor noise: The electric motor which operates the oil unit and blower unit on the oil burner, or an electric motor which may operate a furnace
blower fan or a flue-vent draft inducer fan. However some electric motor noises are "normal" while others indicate trouble, as we
will elaborate below.
Combustion air fan noise: The combustion air blower, usually a squirrel cage fan on oil burners is spun by a shaft extending out of the
oil burner's electric motor. The blower itself produces noise as it spins and moves air into the combustion chamber.
Unless the oil burner blower is damaged you probably won't hear it over the other noises produced at the burner.
Warm air furnace blower noise: Furnace blower fan units: A bad furnace fan blower motor or assembly may produce noise you would indeed hear above the noises coming from
the oil burner itself.
Heating oil pump noises: The oil burner's heating oil pump or "fuel unit" is usually driven by a shaft (and couplings) which begin at the electric
motor on the oil burner, extend through the combustion air blower, and connect to a drive shaft protruding from the oil pump.
Unless there is an internal problem with the pump, these units are pretty quiet compared with other normal oil burner noises.
Draft inducer fan noises: A flue vent connector-mounted or chimney-mounted combustion gas vent draft inducer fan if one is used, is usually audible, and
in a typical installation you'll hear this fan turn on up 15 seconds or so before the oil burner itself begins to operate.
Oil burner combustion noise: Oil burner flame or combustion noise is usually the loudest "normal" noise coming from an oil burner. The fuel unit pumps
heating oil to 100 psi or higher, then sprays it through an oil burner nozzle where the oil is ignited by electrodes mounted
in the oil burner's tube at the entry to the combustion chamber. The "roar" that you hear at a normally operating heating
system oil burner is usually produced mostly by this combustion process.
High speed oil burner noise compared with low speed oil burner noise: High speed oil burners noises: older traditional oil burners used on heating boilers and furnaces were driven by an electric
motor spinning at 1725 rpm. Modern "high speed" heating system oil burners usually run at 3450 rpm. The higher speed permits
more air flow and greater oil burner efficiency. But in buildings where an older low-speed oil burner is swapped out for a
new "high speed" oil burner unit, the occupants are often surprised to hear that the new equipment is noticeably noisier than
the old unit. This is normal, and your heating installer would have been smart to tell you to expect this change so you don't
think something's wrong with the new heating system. You're tolerating more noise for lower heating system operating costs.
What oil fired heating system noises are abnormal and may indicate an operating problem or an unsafe condition?
Noises & soot buildup can lead to a potentially dangerous "puffback" which can damage the heating equipment and blow soot and smoke throughout the building.
An experienced heating service technician may recognize the following diagnostic list of heating system or oil burner noises as well as perhaps other signs of trouble:
Chimney fires: DANGEROUS, IMMEDIATE ACTION NEEDED: Very loud noise like a roaring freight train coming from a chimney is likely to be a
chimney fire- extremely dangerous, risking a house fire: turn off heat as you run out of the house: call the fire department from your cell phone or from a neighbor's house. A chimney fire moves fast, loud, and produces lots of smoke.
In fact a quick look at the chimney serving a heater at any time can tell you how the heating system is operating.
If the chimney top shows smoke or soot (without the freight train noise of a chimney fire) the burner is not operating properly.
If you have a chimney fire (or any kind of fire) stop reading this Internet article, leave the building immediately, and call your fire department. See CHIMNEY INSPECTION & REPAIR GUIDE for details of chimney inspection, diagnosis, and repair, including blocked chimney flues, chimney backdrafting, leaks, and odors from flues. Separately we discuss CARBON MONOXIDE hazards in buildings.
Noises during oil burner startup - a "bang" or "puffback" which blows soot into the room through the barometric damper or through other equipment openings: the oil pump may not be shutting down properly at the end of
an oil burn cycle, leaking incompletely burned oil into the combustion chamber. That oil ignites at startup causing a potentially dangerous puffback. Immediate service and repair are needed.
Noises during oil burner startup - a "rumbling" sound (which usually continues all during operation" or a "stumbling" sound in the combustion chamber probably indicates that the system needs inspection and cleaning very soon. Some noise is normal however, but the normal sounds tend to be more smooth and continuous.
Noises during oil burner shut-down - a stumbling or rumbling after the oil burner motor has stopped, indicate that oil is continuing to leak into the combustion chamber and risks a dangerous puffback - see "Noises during oil burner startup" above. Immediate service is recommended.
Oil burner noises of shrieks or grinding coming from the electric motor or oil pump on the oil burner mean that immediate service is needed - probably a bearing is failing.
Furnace noises of shrieks, whining, or grinding coming from the electric motor or blower assembly of a furnace air handler probably mean that the system has a bad bearing (or fan belt) and prompt repair service is needed. It's best to shut down such a system since
certain failures, such as sucking a furnace filter into the blower assembly, can lead to overheating and cause a fire.
Oil Burner Startup problems: noises and clues of puff back: if you see flapping at the barometric damper or if you see or hear vibrations in the system, prompt service is needed
Noises from radiators or heating baseboards: clanking pipes or sharp snapping noises may be heard as a normal consequence of expansion of metals during the heating cycle. These noises can often be eliminated or reduced
by careful routing of piping and by allowing room around heating pipes for expansion, but probably not eliminated in the case of hot water baseboards.
Bubbling or rumbling noises in hot water heating piping can be caused by air in the heating lines. If the amount of air becomes excessive the
system may be unable to circulate hot water and extra steps to bleed unwanted air will be required. Hissing sounds such as air escaping from
radiators or other piping where air bleeder valves are installed are normal but should be brief and uncommon. If you constantly hear air
hissing from radiator bleed valves double check that you understand what kind of heat you have - hissing from bleeder valves on steam
heat radiators as heat is coming up in the building is normal.
Noises from Oil Tanks or Oil Piping: Vibrations of the heating oil piping, especially if installed passing overhead along building framing and if installed without sound isolation can use the ceiling as a giant speaker and may be quite loud.
Noises from air leaks: on furnaces (hot air systems) we sometimes find that an air leak in the duct system or air handler, or quite often
around the air filter itself, can make lots of noise.
What can we do to reduce heating system operating noises?
Heating equipment located well out of occupied space, in an unoccupied basement, for example, are not usually a source of noise complaints in
a building, though there are a few exceptions for which we have suggestions.
Consult your heating service technician first to be sure that the heating system is operating normally and safely, before
attempting any other steps to reduce noises coming from the heating system.
How to cure vibrations of the heating oil piping or oil tank: re-route piping between the oil tank and the oil burner
to remove any contact points with overhead ceiling framing or flooring; if those contact points are necessary to support the line, be sure
that the oil line is supported with noise-suppressing fittings (we use foam rubber and copper pipe clamps) and that the piping
is well secured.
How to cure warm air heating system air duct or filter noises see
Under-sized Return Air Ducts can cause excessive duct noise since
inadequate return air means the system is "return-air starved" and will suck air into the duct system at any available (and noisy) opening.
Oil Burner Noise Insulation: some of our readers suggest building an insulated box around the oil burner to reduce its noise.
Watch out! If you constrict or reduce the amount of combustion air available to the oil burner it will not operate properly and the system
could become unsafe. Be sure to discuss the design of any noise insulation scheme and its possible effects on combustion air or other heating
system considerations with your heating service technician.
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Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Carson Dunlop, Associates, 120 Carlton Street Suite 407, Toronto ON M5A 4K2Toronto. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, 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
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
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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