How to Diagnose Oil Burner Noise, Smoke, Odors - Defects & Operating Problems Found on Hot Water Heating Boilers

• How to Diagnose Oil Burner Noise, Smoke, Odors
• Diagnose & repair oil burner soot, puffback, rumbling, hard-starting
• Flue gas exposure hazards, smells, odors
• 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

How to Diagnose Noises & Odors During Heating System & Oil Burner Operation

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.

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.
  
  George Lanthier (Fuel Oil News) reported on customer complaints about the increase in noise when new, more energy efficient but noisier oil burners are installed. In a 2006 article in that publication he offered several suggestions of which his first is that oil companies should "scare the dickens out of the customer" meaning that the vendor should prepare the client for an increase in heating system noise level.
  • Oil burner mechanical noise: Break the noise levels down by area in the equipment: is the noise from the burner itself? He argues that the burner mechanical parts are pretty quiet (barring a bad bearing or motor-DF);
  • Oil burner flame noise: draft conditions can affect flame noise, but Lanthier skirted the basic fact that doubling the burner speed along with concomitant higher oil and combustion chamber pressures increase noise levels. Careful selection of oil burner nozzle, flame retention head and head settings may reduce this noise a bit.
    • Switching to intermittent oil burner ignition (most residential burners run the igniter all during burner operation) may reduce burner flame noise and also reduce NOX emissions. A service tech can test for this benefit by installing a jumper to permit temporary turn-off of the ignition circuit once flame is established. (Appropriate safety controls must also be installed).
    • Hollow-cone oil burner nozzles may reduce flame noise. Indeed we (DF) recall from oil burner service days that changing the oil burner nozzle to a flame type and pattern that better matched the burner and combustion chamber could make a large difference in how the burner and flame behaved and sounded.
    • Measure the system standard heating tuneup parameters including smoke and CO₂ to verify that your adjustments have improved, not hurt, system performance. We often found better combustion efficiency using hollow-cone oil burner nozzles -DF.
  • Chimney noise: In Lanthier's opinion this is the most serious noise problem from heating systems. Certainly we'd agree that many chimneys act as sound amplifiers and transmitters through a building. But
    Watch out for chimney fires: a roaring freight train sound that means a deadly dangerous fire is occurring (more likely with a wood-stove). More on chimneys is at Chimneys & Chimney Fires. Steps to reduce chimney noise, assuming we don't have a dangerous condition, include:
    • Install a chimney liner (have this done by a professional, certified chimney service company) to reduce noise, condensation problems, and oversized flues that may create venting and even safety problems. See NFPA31-2001, National Fire Protection Association and read all of Appendix E, “Relining Masonry Chimneys” .
    • Litman chimney elbow: Lanthier describes an idea from Roger Litman (North Shore Fuel) who adds an elbow at the end of a flue pipe run in the base of a chimney to reduce chimney noise. The elbow both reduced noise and improved chimney draft, perhaps because the elbow adds length and thus velocity to incoming chimney vent products. Add a drainage hole in the low point of the elbow, and "get the outlet of the elbow to angle about 15 degrees to the base".
  • Watch out: Too-Quiet Chimneys can mean big trouble: Lanthier explained that a blocked chimney flue can reduce heating system noise below normal levels, but of course a blocked chimney is dangerous, risking a fatal carbon monoxide poisoning condition as well as improper and unsafe heating boiler or furnace operation and damaging the burner itself (backpressure-burning off the burner end).

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.
  
  Watch out: 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
  • Loose or Leaky Air Conditioning or Heating Ducts
  • Vibration Dampers & Asbestos at the Air Handler - make sure your vibration damper is properly installed, sized, and not leaky.
  • 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.
  • An Analysis of the Effectiveness of Air Filters on HVAC Systems includes discussion of air bypass leaks at air filters. Be sure to review this noise source as it's easy to correct.
• 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.