Oil burner smoke test example (C) Daniel FriedmanOil Burner Tests & Adjustments: How to Measure & Set Oil Burner Combustion Air & Smoke Levels

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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 evenm 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.

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Oil Burner Smoke Test - Indicates Proper Combustion Air, Draft, Burner Adjustment

Oil burner smoke test equipment, Bachrach Kit (C) Daniel FriedmanIf the oil burner is not working, start your diagnosis at OIL BURNER INSPECTION & REPAIR.

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.

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.

  • 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.

Oil burner smoke test example (C) Daniel FriedmanZero-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".

Setting an Oil Burner for Zero Smoke?

Setting an oil burner to zero smoke (C) D FriedmanTechnical 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.

To perform this 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.

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.

Also see COMPLETE COMBUSTION, STOICHIOMETRIC for an explanation of complete fuel combustion and boiler or furnace maximum efficiency.

Thanks to Bob, a heating service technician at Bottini Oil, for this service tip.

Oil Burner Smoke Numnber Standards

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.[5]

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

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. There we explain 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 DIAGNOSIS REPAIR for details of chimney inspection, diagnosis, and repair, including blocked chimney flues, chimney backdrafting, leaks, and odors from flues.

Combustion Analyzer Recommendtions & 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 Tel: 724-334-5000 Fax: 724-334-5704 E-mail: Help@MyBacharach.com
  • Bosch smoke testing & smoke numbers [data needed]
  • Hartridge smoke testing & smoke numbers [data needed]
  • Uei Test Instruments, UEI 675 combustion analyzer ($775 U.S. Amazon.com), Uei D460 Draft Gauge, Website: http://www.ueitest.com/, UEI Test Instruments, Portland, OR 8030 SW Nimbus Beaverton, OR 97008 Tel: 503 644-8723 Tel: 1-800-547-5740 Fax: 503 643-6322 Email: info@ueitest.com
    UEI Test Instruments, 8030 SW Nimbus Beaverton, OR 97008 Tel: 503 644-8723 Tel: 1-800-547-5740 Fax: 503 643-6322 Email: info@ueitest.com

Also see COMPLETE COMBUSTION, STOICHIOMETRIC for an explanation of complete fuel combustion and boiler or furnace maximum efficiency.

Continue reading at OIL BURNER CO2 TEST or select a topic from the More Reading links shown below.

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