Oil Burner Tests & Adjustments How to Measure & Set Oil Burner Combustion Air & Smoke Levels
OIL BURNER SMOKE TEST - CONTENTS: Guide to oil burner operating tests: Bachrach or Bosch Smoke Numbers. How to measure oil burner smoke level to evaluate system efficiency and operation. What is the correct smoke level for oil burners. What is the proper air shutter adjustment position on an oil burner? How to Diagnose Oil Burner Noise, Smoke, Odors. Diagnose & repair oil burner soot, puffback, rumbling, hard-starting.
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Oil burner smoke test which in turn reflects combustion air & temperature adjustment are necessary for safe, efficient and reliable oil burner operation: this article explains and illustrates oil burner smoke testing - a key step in oil burner adjustment for proper operation.
An oil burner flame that is too smoky soots-up the heating system leading ultimately to a no-heat call and a clogged furnace or boiler or water heater. An oil burner flame that "looks very clean" may in fact be running too hot, wasting fuel, increasing heating costs, damaging equipment, or perhaps even unsafe. This article describes how we measure the oil burner smoke level and describes the proper smoke settings.
This article series answers most questions about central hot water 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.
The basic measurements made by any competent oil heat service technician include the stack temperature, draft, smoke level, and carbon dioxide level (OIL BURNER CO2 TEST).
These data tell us whether or not the equipment is properly adjusted and operating safely and economically. Here we explain how we measure the Bachrach or Bosch smoke numbers - a slightly subjective evaluation of the level of smoke or "soot" found in oil burner exhaust flues.
One of these most basic tests performed by an oil heat service technician is the "smoke test" using a strip of filter paper and a pump to sample the oil burner exhaust, measuring the level of smoke in the exhaust. In fact once an oil burner has been installed or just after the oil burner has been serviced, the service technician will usually start her system tuning and adjustment with a simple smoke test.
Our photo (left) shows a traditional smoke testing pump (the black cylinder with a handle at its right end) used for decades. This equipment was produced by Bachrach, an oil burner test equipment manufacturer.
Steps in Conducting an Oil Burner Smoke Level Test
The technician allows the oil burner to reach normal operating temperature (perhaps after it has been on for five minutes),
A clean white strip of filter paper is inserted into the end of the smoke testing pump.
The nozzle of the smoke tester is inserted into a 1/4" diameter hole in the flue vent connector pipe, typically just a few inches above the top of the oil-fired heating boiler or furnace.
The pump is operated
The filter strip is removed and the "blackness" of the sample spot is compared with a scale that rates the soot level. An experienced oil heat service technician simply looks at the black or gray spot on the filter paper.
Watch out: as we have written in several articles, it is impossible to do a good job cleaning and servicing oil fired heating equipment without getting dirty.
But if you put your sooty fingers all over the filter paper before or after conducting a Bachrach / Bosch smoke test, then soot from your hands will get onto the filter paper and you may mistake a 0 smoke reading as a 1 or 2 level smoke. Don't touch the smoke sample test area with your dirty fingers.
Zero-level smoke in a Bachrach / Bosch test is actually "too clean" for most oil burners, and means that there is too much air entering the oil burner, causing the burner to operate too hot, and sending too much heat (and thus the money the homeowner spent on heating oil) up the chimney.
The correct smoke level is just a "trace" of smoke on the filter paper, a level of 1 is good.
A smoke level of "1" or "2" is normal. In our oil burner smoke test results photo (at left) you can see four smoke test samples. Sample #1 is certainly too dirty, sample #2 and sample #3 are a bit high, though we might accept sample #3. Sample #4 is just slightly above zero and is a good setting.
Watch out: sorry for the labels in our photo at left: Don't mix up our sample numbers #1 - 4 with smoke level values = 0,1,2,3, etc. A smoke level of 0 means there is no black soot visible on the filter paper.
The Bachrach or Bosch smoke number scale ranges from 0 (no detected smoke) to 9 (solid black). In addition to using the hand operated smoke pump illustrated here, some electronic combustion analyzers can also produce a smoke level number. [Click any image or table to see an enlarged, detailed version.]
Higher smoke levels indicate that the system is operating too "dirty" or smoky. High levels of soot in the oil burner exhaust mean that the system will deposit soot more rapidly inside of the furnace or boiler heat exchanger, interfering with heat transfer into the building heating air or water, and thus increasing system operating cost - meaning higher heating bills and more frequent oil burner service needed.
Very high smoke levels may indicate or even cause plugging up of the furnace or boiler, leading to improper oil burner operation, an unsafe system, and possibly other malfunctions, even a "puffback".
Should we Set The Oil Burner for Zero Smoke?
To perform the oil burner "smoke" adjustment correctly and to avoid over-firing or overheating the boiler, as well as to avoid an inefficient set-up that sends too much heat up the chimney, the heating service tech will first set the oil burner for just a trace of smoke (#1 in our photo at left), then s/he will slightly increase combustion air until the trace just vanishes to a zero smoke reading (#2 and #3 in our photo) with the test filter paper and smoke gun.
Technical note: on some modern oil fired heating systems the oil burner combustion air and oil pressure are adjusted to a standard of zero smoke rather than a trace of smoke.
Watch out: Other measurements including stack temperature, draft, and CO2 are required to properly and safely set up an oil burner.
Watch out: Don't come at zero smoke from a position of too much combustion air or you won't know what you've got and you may be wasting fuel and overheating the equipment. Thanks to Bob, a heating service technician at Bottini Oil, for this service tip.
While technicians and equipment suppliers commonly refer to a Bachrach smoke number or Bosch smoke number, these smoke measurements are also standardized in ISO 10054
Actually there are at least eleven different smoke level measurement standards. Homan (1985) reports on standardization among these.
The second common test performed by an oil heat technician evaluates the oil burner efficiency by measuring the carbon dioxide level or CO2 level in the oil burner exhaust.
Details of measuring the carbon dioxide level for oil burners, a second key measurement needed for proper setting of oil burner combustion air & operating temperature are now at OIL BURNER CO2 TEST
Combustion Analyzer Recommendations & Sources of Oil or Gas Burner Combustion Testing Kits include Oil Burner Smoke Level Measuring Devices
Bachrach Inc. provides the Fyrit ® Classic Oil Kit (shown in the case photos above) for testing oil or gas burners, as well as a number of other test instruments such as the Fyright® Insight® Plus (electronic), Fyrite Intech®, the ECA450, and the PCA 3 portable combustion analyzer. Website: http://www.bacharach-inc.com/combustion-test-kits.htm, Bacharach Sales/Service Center
621 Hunt Valley Circle
New Kensington, PA 15068-7074
How does the oil burner tech adjust the Air Shutter on an Oil Burner? Combustion air adjustment procedure.
"Set the oil burner smoke level" as we mention in the article above at OIL BURNER SMOKE TEST, means that the service technician will have to adjust one or more of the following in order to obtain the desired trace of smoke on the smoke test or zero smoke + a specified operating temperature range if that alterative is called for by the oil burner manufacturer.
At left you can see that the pointer on the air shutter on this Beckett Model AF oil burner is set to an index number of 3 1/2. The oil burner is sensitive to small changes in intake air. At that 3 1/2 setting you can just barely see an air opening at the top and bottom of the large shutter openings - those two small black areas.
[Click to enlarge any image].
The air intake shutter at the oil burner is adjusted by loosening one or two clamping screws, then rotating the air shutter to a higher index position to increase or to a lower index number to decrease the rate of air flow into the oil burner. This adjustment is made first, then the technician measures either O2 or CO2 to make further adjustments.
Most newer oil burners such as the Beckett™ series include index marks along the side of the oil burner body and a pointer attached to the oil burner air shutter. There may also be a label affixed to the oil burner OR a table in the oil burner's instruction manual that suggests a recommended intake air shutter position for various oil burner nozzle sizes (in GPH).
Beckett recommends that after you've set the oil burner to give just a trace of smoke using a smoke tester, then you open the air shutter until this level changes (from a presumed slightly higher measurement) down to 12.0% CO2 or 4.5% O2. That gives an efficient and seasonally-clean oil burner operation with a slight safety margin without overheating the system.
Watch out: particularly with newer high-speed, higher efficiency oil burners, if there are other air leaks such as around the transformer at the upper rear of the oil burner assembly you may have trouble setting and regulating the desired burner intake air rate. Be sure that the plate mating the transformer to the oil burner top is flat, not bent, and remember to tighten the screws that hold the hinged-type transformer front end down snugly in place.
Watch out: while back in the "old days" it was reasonable to "tune" an low speed (1725 RPM) oil burner by eye with a bit of spit and guesswork, that is not the case with modern, high speed (3450 RPM) oil burners. In fact the flame may not even be visible, and spitting on the flue vent connector is no longer an adequate measure of temperature, nor of CO2. Instead the oil heat service technician must make use of instruments to measure draft, temperature, CO2 or O2 as well as smoke level.
Other draft controls such as a barometric damper may need adjustment. Typically we look for 0.02" WC (water column) over the fire and 0.04-0.05" WC 5 in the breech, the section of flue vent connector between the top of the boiler or furnace and the barometric damper or draft regulator.
The draft in the breech must always be higher than over the fire, otherwise you're running your oil burner in a backpressure condition, causing overheating, damage and unsafe conditions.
If you cannot obtain proper draft measurements chances are that the chimney is blocked (draft too low) or there are openings in the chimney such as an ash pit door left open (draft too high).
CO2 or O2 are measured both to obtain a picture of how efficiently the oil burner is operating and also how safely. Typically we'll see a tuned oil burner running at about 12-13% CO2 or at about 2.5-4.5% O2.
Exhaust gas temperature should always be measured in the breech as part of an oil burner tuneup, as too high a temperature tells us that we're sending oil costs up the chimney unnecessarily and that the system may be unsafe, while too-low a stack temperature may indicate inadequate combustion.
Heating sources such as Beckett, cited below, provide oil burner tuneup details including an oil burner net efficiency table relating stack temperature and CO2 or O2 levels measured in the breech.
For example at a too-low O2 level of just 1% and a too-high stack temperature of 600 °F, the oil burner will be running at about 80.6% efficiency: about 20 cents of the heating oil dollar is going up the chimney. If we tune that system to an O2 level of 4% and a stack temperature of 350 °F, the efficiency will improve to about 85.1%.
Now about 15 cents of the heating oil dollar is going up th chimney: a reduction of the original flue loss by 25% and reduction in annual heating cost by about 6%.
Watch out: high stack temperatures, say over 500 °F and certainly over 600 °F probably mean that the heat exchanger in the boiler or furnace is soot-clogged: you're not transferring heat from the combustion gases into the boiler water or building air; instead you're sending it up the chimney. At 800 °F and 12% CO2 you're sending 18 cents on the dollar up the flue.
One should also worry about the increased risk of a building or chinney fire when operating a heating system at abnormally high temperatures.
Watch out: direct-vent oil fired heating equipment will not use a conventional chimney nor barometric damper, but the combustion air, air shutter, and other oil burner adjustments are still required for proper and safe operation.
Hartridge smoke testing & smoke numbers [most used to examine exhaust in diesel engine work]. A Hartridge smoke test value of 0 indicates perfect "combustion" or "transmissin", or zero opacity.
A Hartridge smoke units (HSUs) a test value of 100 indicates total absorption, or complete opacity. For Hartridge Smoke Units (HSU) technically this measurement is referenced to a transmission length of 430mm, at 100°C and atmospheric pressure. Values in between are not linear with respect to actual light absorption.
Smoke Factor (SF) used by ESPH to describe a remote smoke level sensor result: the ratio of exhaust opacity to the amount of fuel being burned at the time of measurement.
Black diesel smoke with an SF of 1 means that 1% of the fuel mass is passing through the combustion process to be emitted as particulate matter (PM).
Or see HEATING SYSTEM INSPECTION PROCEDURE an organized approach to inspecting the entire heating system, beginning outdoors, continuing indoors, and ultimately in most detail in the boiler or furnace room.
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 Beckett Corporation, 38251 Center Ridge Rd.,
North Ridgeville, OH 44039 440-327-1060 Email: firstname.lastname@example.org supplies residential and commercial oil burners for boilers, furnaces, and water heaters - see www.beckettcorp.com/
 Thanks to Bottini Fuel service. Bottini Fuel is a residential and commercial heating oil distributor and oil heat service company in Wappingers Falls, NY and with offices in other New York locations. Bottini Fuel, 2785 W Main St, Wappingers Falls NY, 12590-1576 (845) 297-5580 more contact information for Bottini Fuel
 Audels Oil Burner Guide, Installation, Servicing, Repairing, Frank D. Graham, 1947 edition (obsolete, out of print). See Brumbaugh, James E. Audel HVAC Fundamentals, Volume 2: Heating or see various versions of this guide available in editions from 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. Used copies are available at Amazon.com
 Homan, H., "Conversion Factors among Smoke Measurements," SAE Technical Paper 850267, 1985, doi:10.4271/850267
Abstract from SAE:
A set of smoke measurement conversion equations are derived. The equations convert any of eleven smoke measurements to the other ten measurements. The eleven measurements are: Bosch, SAE, and ASTM (Bacharach) smoke numbers, Hartridge opacity, PHS opacity, Calesco model C107 opacity, extinction coefficient, transmittance, opacity, fraction of fuel carbons converted to smoke, and mass fraction of smoke in the exhaust gas. These eleven smoke measurement methods are described along with a general explanation of the consonance of smoke measurement methods, which allows one to derive equations for interconverting them. A FORTRAN program is listed which performs the conversions. The predictions of the program are shown to be within the scatter of published experimental data. However, published experimental data varies by as much as a factor of two. The conversion equations enable experimenters to choose a smoke measurement method which is sensitive to expected smoke concentrations. - retrieved 10/24/2013, original source http://papers.sae.org/850267/
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
The Home Reference Book - the Encyclopedia of Homes, Carson, Dunlop & Associates Ltd., Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of the Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ®
sup> author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
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. Used copies are available at Amazon.com
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.)
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones