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 oil fired central hot water heating boilers or warm air furnaces
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Here we discuss how to inspect oil burners used on oil-fired heating boilers or furnaces. 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. Readers should see HEATING SYSTEM INSPECTION PROCEDURE where we discuss an organized approach to inspecting the entire heating system, beginning outdoors, continuing indoors, and ultimately in most detail in the boiler or furnace room. 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.
This article is in process, critique or contributions are invited. Contact Us.
Visual Inspection of Oil Burners on Heating Boilers, Water Heaters, Furnaces
If the building heating equipment is simply not working, start at Heating Loss Diagnosis. In the oil burner inspection article provided here we discuss visual and other clues of oil burner problems.
An expert inspection of an oil burner begins either with having made note of building owner/occupant concerns (noises, odors, no heat, high fuel costs), or with having made some basic visual observations outside: a sooty chimney top, for example. The sketch is courtesy of Carson Dunlop. )
The oil burner inspection continues indoors, even before entering the utility room where the oil burner (or often more than one of them if oil fuel is used for both heating and a separate water heater) is located: look at the building interior as you enter: are there odors, soot deposits, noises associated with the heating system?
The oil burner inspection becomes detailed, and diagnostic, when you can actually see the equipment. It's obvious that you should notice oil leaks, soot in the boiler or furnace room, noises, odors, signs of repeated repairs, piles of junked parts, signs of unprofessional work (covers off of controls, sloppy wiring or plumbing). But just what each of these clues might mean bears some additional explanation that we offer below.
Outdoor Clues of Oil Burner Troubles
How old is the building? Is it likely that older oil fired heating equipment is or was installed?
Where is the oil storage tank? Is it outdoors, subject to water, condensation, gelling? Let's not just blame the oil burner for problems if there are other issues at the property that can impact oil burner operation. Also see OIL TANK LEAKS and see OIL TANK PIPING DEFECTS.
Soot at the chimney top of the flue used to vent oil fired equipment almost always indicates that the oil burner is or was operating poorly, producing smoky sooty exhaust. You might even see smoky exhaust if the oil burner is running while you are approaching the building. So take a look at the chimney(s) before you go indoors.
If the chimney top is sooty we don't yet know the cause of poor oil burner operation but we know there is a problem. If your inspection of the chimney top, even from ground level, perhaps with binoculars, shows water, frost, or mechanical damage to the chimney itself, or a missing chimney cap, these conditions may not only affect the operation of the oil burner, but they may be very unsafe. See CHIMNEY INSPECTION DIAGNOSIS REPAIR.
Indoor Clues of Oil Burner Troubles
On entering the building or by customer interview,
Are there signs of water leaks onto or into the oil burner, boiler, or furnace? As our house fire investigation photographs show (above/left), water passage down a chimney (say from a missing chimney cap) easily continue into the heating boiler or furnace where they may cause damage to the oil burner, boiler, furnace, or its controls.
Oil burner and boiler damaged from building fire:
Notice those rust stains below the oil burner inspection port above and to the left of the burner tube? This oil fired heating boiler has been flooded. The photo at above left shows the probable passage of water entry, down the flue. While the basement of this building was reported not to have contained substantial water (notice there are no flood lines on the outside of the heating boiler itself), water from above during extinguishment of a house fire ran down the chimney and flooded the boiler itself. Inspection and possibly repairs are needed before this equipment can be safely used.
Signs of Trouble at the Oil Tank that Cause Oil Burner Problems
We mentioned outdoor oil tank problems above, but even indoors you may spot signs of trouble that affect oil burner operation.
An oil leak anywhere in the oil piping between the oil storage tank and the oil burner will usually cause improper oil burner operation - leaks of oil out of the oil piping become air leaks into the oil piping system when the oil burner is running and trying to draw oil from the oil storage tank. Air leaks in the oil piping and burner cause improper oil burner shutdown, spewing unburned or only partially burned oil at oil burner shut-down, and risking dangerous (and sooty) puffbacks as well as telltale noises at oil burner start-up.
Boiler or Furnace Room Clues of Oil Burner Troubles
Identify the heating system components in each building area. How old is the equipment, what are the signs that parts have been replaced (new transformer, new valves, new oil piping, new filters, new fuel units, discarded parts nearby). Oil burner controls may themselves be a source of trouble - See Cad Cell Relay Switch Flame Sensors and Stack Relay Switch and also See Aquastat Functions and THERMOSTATS. For oil fired warm air systems also see FAN LIMIT SWITCH control on heating furnaces. Controls for oil fired steam heating systems are discussed at Steam Heating Systems.
Look for damage to the furnace or boiler itself: if the boiler or furnace is old, cracked, rusted-through, leaking, damaged, repairing the oil burner may be the least of the owner's risks. And if the boiler, furnace, or water heater is unsafe or needs immediate repair or replacement, fixing the oil burner and leaving the job is dangerous.
Our photo (left) shows a furnace that should not be used, and needs immediate replacement. Fixing its oil burner, or even inspecting it would be foolish - this furnace should be left shut down, red-tagged, and appropriate oral and written warnings issued. If the furnace, boiler, or water heater has had a safety recall, that's critical information for the owners to know about. For example, see Blueray Heating Boilers/Furnaces Safety Recall by the US CPSC, with additional history, photos, and technical details.
Look at the heating equipment's service tag: has the equipment been serviced annually; are there records of other no-heat service calls - often a good service tech will note on the service tag the no-heat call, the diagnosis, and what parts were replaced. At Heating Cost Reduction Advice: How to Save on Home Heating Costs, we discuss heating tuneup tips for oil burners to reduce heating cost.
Oil fired equipment efficiency measurements: If you do not see a small (roughly 1/4" diameter) hole in the flue vent connector just above the boiler, before the barometric damper, then this heating equipment has never been properly tuned and measured for proper operation. While it was possible to "eyeball" older oil fired equipment (spit on the flue for temperature and blow cigarette smoke at the burner for draft), modern oil fired equipment requires more accurate measurement and adjustment for good operation.
As our sketch from the Audel Oil Burner Guide shows, measuring the stack temperature and CO2 level gives a critical indication of the heating system efficiency, in other words, measuring what percent of each dollar spent on heating oil is going up the chimney versus into the building as heat. The Guide also includes this chart of oil fired heating system efficiency at different CO2 levels and stack temperatures.
The little hole we describe is where the service tech inserts test equipment to measure stack temperature, smoke level, and CO level. Some techs use two holes to permit more than one measurement simultaneously. No hole = never measured. (Or new flue vent connector parts have just been installed on older equipment and no one has made a hole yet.)
At the heating boiler or furnace, identify the fuel source and follow fuel supply piping to its source (an oil tank, LP gas tank, or
gas meter, for example) - you may spot the oil leaks and piping problems we mentioned above.
Look at the oil burner combustion air supply - it's remarkable how often the oil burner service tech tunes up the system with the door to the boiler or furnace room open (who wants to work in a little closet), then leaves, closing the door, and shutting off the only combustion air supply to the equipment - a likely cause of sooty operation and other troubles. See COMBUSTION AIR DEFECTS.
Look at the furnace or boiler connection to the chimney - the flue vent connector, barometric damper, and for signs of trouble with the chimney itself (no cleanout door, air leaks, blocked flue).
Look at and look into the barometric damper or draft regulator: is there one installed, is it properly installed, is the flue thick with soot, is soot blowing out of the draft regulator? Our photo, left, shows so much debris in the breech of this oil fired heater that the oil burner is likely to see trouble itself.
See DRAFT REGULATORS, DAMPERS, BOOSTERS for details.
Signs of Trouble at the Oil Burner Itself - Visual Inspection
Are there signs of backpressure in the combustion chamber? The cause may be a dirty boiler or furnace, a blocked flue, inadequate draft, etc.
We have seen oil burners that suffered through three or four transformer replacements, in one job every few months: the service tech had not realized that chimney problems and backpressure were causing so much heat blow-back into the oil burner tube that the transformers were being "cooked" - the clue was obvious if you knew that tarry goop leaking out of a transformer means it's overheating.
Our photo of backpressure burns at an oil fired boiler (left) shows rust around the inspection port - a hot combustion chamber has burned off the paint in this area.
The oil burner itself, a Beckett oil burner, was tolerating the backpressure in this case and was undamaged. But the backpressure cause (a dirty boiler) needed to be addressed. More often we see soot around the oil burner as a sign of backpressure, such as this horizontal furnace oil fired unit backpressure photo.
Are there oil leaks at the oil burner or at the fire-o-matic fusible link oil valve (that should be installed at the oil burner burner) or at the oil tank? See OIL SAFETY VALVES. Also see OIL TANK PIPING DEFECTS.
Is the system safely connected to a chimney? If not, stop worrying about the oil burner and shut the system down.
Look at the temperature/pressure gauge: normal operating values? Boiler temperature and pressure are indicated on the TP gauge and should show increase not to exceed normal operating limits (200 deg F or less and less than 30 psi) - Gauges on Heating Equipment.
If the aquastat settings controlling a hot water heating system boiler are set to unusual temperatures that may indicate an operating problem, a heat distribution problem, an un-trained service tech, or homeowner meddling. On hot water heating boilers, the pressure and temperature gauge reads about 12 psi cold, less than 30 psi hot. Over 30 psi the temperature will cause spillage at the temperature/pressure relief valve.
Typical operating temperature
settings LO-120-160 HI-180-200 degF.
Typical operating temperature observed at the gauge will be below the high, and can be as low as
nighttime room temperature in non-heating season if no tankless coil is in use. The temperature/pressure gauge may help in checking for
normal conditions before and during boiler operation. However the gauge can be wrong! - Gauges on Heating Equipment
Furnace temperatures on oil burner-fired warm air heating systems are not normally measured by a gauge but are reflected on the settings of the FAN LIMIT SWITCH.
Steam boilers and their oil burners in most residential installations operate at low pressure (a fraction of 1 psi) - if the steam boiler pressure switch is set high, that may indicate a heat distribution problem that has been "fixed" using an expedient but improper approach. (See Steam Heating Systems).
Oil burners on water heaters use similar (but generally simpler) high limit and low limit temperature controls but a temperature/press rue relief valve that is designed for water heater operating temperatures and pressures.
Water leaks at valves or fittings which drip into the jacket of a steel boiler or onto controls or zone valves or for warm air systems, plumbing leaks onto the furnace, or condensate leaks from a combination heating and air conditioning system that drip onto the heat exchanger risk failure, dangerous carbon monoxide gas hazards, and
ultimately loss of heat.
Oil burner air shutter debris, dirt, or shutter adjustment problems or inadequate combustion air; because there is invariably a thin oil film on these parts, building pets, especially dogs and cats, may shed hair that collects-on and blocks combustion air entering the oil burner. Our photo (above right) shows our pen (photo above right, at bottom center) pointing to the very small opening in the air shutter at this Beckett oil burner. You can see that even a small amount of cat hair sticking on this opening will easily block the flow of combustion air into the oil burner, thus causing improper (and sooty) oil burner operation. In this photo the opening is not blocked by debris, though we see a little soot there.
Oil leaks at air bleed valves or other fittings on the fuel unit on the oil burner. In our photo (above left) our pen points to the bleeder valve used to purge air from the oil line; Look for oil drips here as well as at the oil line fittings (shown in the bottom of the oil burner fuel unit in this photo).
Signs of Trouble at the Oil Burner - During Operation
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.
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:
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.
Oil burner electric motor off on reset - if the reset switch on the electric motor that drives the oil burner keeps going off (see Reset Switch - electric motors) you'll need help from a trained service technician to determine the problem.
Signs of Trouble Inside the Oil Burner - Simple Disassembly, Inspection, Testing
We look for obvious trouble signs before making any changes or adjustments to the oil burner assembly by turning off power to the equipment, shutting off the oil supply line at the closest service valve, and opening the oil burner for inspection. Our sketch (left) shows how an oil burner gun atomizes and sprays heating oil into the combustion chamber - Audel Oil Burner Guide
Most oil burners are opened by loosening two screw clamps at the front of the transformer box mounted atop the oil burner tube and folding the hinged transformer back to expose the interior of the tube, the oil burner nozzle assembly, and other parts. Some obvious trouble signs inside the oil burner include:
Cad cell sensor sooty or dirty (probably from backpressure in the combustion chamber combined with sooty operation - can force an oil burner to remain "off on reset" when the cadmium cell sensor that informs the safety control cannot sense that a flame is present. See Cad Cell Relay Switch Flame Sensors for details and also see Reset Switch - Primary Control.
racked, damaged ceramic electrode insulators on the oil burner assembly - a short here will cause improper ignition
Dirty turbulator assembly (if present) mounted on the end of the oil burner nozzle - can interfere with proper air flow around the nozzle and thus with proper heating oil combustion. The turbulator is a fan-like collection of fins that is mounted, usually on the end of the oil burner nozzle by a bracket, and that provides increased air turbulence to improve heating oil atomization and spray pattern, thus improving combustion efficiency. Debris and soot can block the air space between the turbulator blades, causing this device to stop working, and leading to dirty sooty oil burner operation.
Dirty oil burner nozzle, especially crud build-up that is blocking oil flow or shorting out the oil burner nozzle electrodes - see OIL BURNER NOZZLE & ELECTRODES
Loose, damaged, mis-aligned oil burner electrodes (use a simple oil burner nozzle gauge or a small steel rule to see that the position of the oil burner electrodes in their gap apart, their distance above the oil burner nozzle orifice, and their distance forward or backwards relative to the face of the oil burner nozzle are according to the manufacturer's specification. See OIL BURNER NOZZLE & ELECTRODES for details.
Damaged squirrel cage blower assembly - loose, wobbly bearings, bent fins, dirt and debris; this problem will reduce combustion air input to the oil burner and will result in poor, sooty operation.
Damaged coupling joining the electric motor that drives the oil burner, the combustion air blower squirrel cage fan, and the shaft that turns the fuel pump unit itself.
Oil and debris inside the oil burner tube - possible leaks, incomplete combustion, improperly mounted oil burner gun assembly
Overheating inside the oil burner tube, tarry goop leaking out of the transformer assembly
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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.
Beckett Corporation, 38251 Center Ridge Rd.,
North Ridgeville, OH 44039 440-327-1060 Email: sales@beckettcorp.com supplies residential and commercial oil burners for boilers, furnaces, and water heaters - see www.beckettcorp.com/
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
Audels Oil Burner Guide, Installation, Servicing, Repairing, Frank D. Graham, 1940's edition (obsolete). Updated versions of this guide are available in various editions, 1947, 1950, 1955, 1958, 1959, 1962, 1965, 1967, and at prices from around $3.00 to nearly $70.00 - useful for simple, clear, but not current, explanation of how heating equipment works. The original retail price was $1.00.
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.
"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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