Oil Burner Carbon Dioxide Test

How to Measure & Set Oil Burner CO₂ or O₂ Levels for Efficient Oil Burner Operation

Oil Burner CO₂ Test - Carbon Dioxide Level Test Tools

Above: the author's (DJF's) Bacahrach Fyrite Combustion Analyzer kit containing a CO2 or CO gas tester, a smoke tester, and a draft gauge (not shown) and a thermometer (not shown).

Bacarach combustion analyzer equipment including the company's current Bacarach Fyrite INSIGHT Combustion analyzer is sold at HVAC suppliers such as Grainger and SupplyHouse. (Bacarach is currently a part of MSAsafety.com.)

If the oil burner is not working, start your diagnosis

at OIL BURNER INSPECTION.

The basic measurements made by any competent oil heat service technician include the stack temperature, draft, smoke level, and carbon dioxide level.

Along with OIL BURNER SMOKE TEST, 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.

While there are electronic sensors used by some technicians for this purpose, many oil heat service tech's continue to use the time-tested Bachrach Fyrite™ oil burner tester shown below.

Our photos show the rubber bulb and tubing used to pump oil burner exhaust gases into the CO₂ level tester (the bulb and tubing atop the smoke tester, above left),

and a closeup of a well-used CO₂ tester (below).

Measurement is made at the same flue vent connector location as we discussed above.

The classic Fyrite gas analyzer shown above has been discontinued and is replaced by the Bacarach Combustion handheld electronic analyzers that communicate with a smartphone application.

Shown below, a modern approach to measuring CO₂ using the Fyrite II from Bacharach (often misspelled as Bachrach)

Watch out: if your heating oil company does not provide working test equipment for the service technician, setting the oil burner adjustments is going to be done by guesswork.

The result is likely to be either higher heating costs over the season for a system that is running too hot, or higher heating service costs for a system that runs too dirty.

In fact when the author (DF) attended oil burner school we were taught to make two openings into the flue so that smoke level and CO₂ measurements could be made through one opening while a thermometer or draft gauge monitored those two additional data points at the second opening.

• The CO₂ tester is filled
  
  with a red fluid that changes volume in response to carbon dioxide level.
  
  The Fyrite test unit is inverted, returned to upright, tilted at 45 degrees, to prepare it for use and to calibrate or set the "zero point" on the CO₂ gauge.
  
  A cap on the unit is depressed to vent the unit to the atmosphere and the zero point is set on the adjustable gauge.
• Exhaust gas is pumped into the CO₂ tester,
  
  the tester is treated with flue gas exhaust for the required number of strokes (18) to purge the tubing and bulb and analyzer (tester).
  
  Why so many puffs of the rubber bulb? Remember you have to purge ambient air out of the tubing, the bulb, and the test instrument to be sure your sample in the instrument is of flue gas.
• The analyzer is inverted,
  
  then returned to upright, tilted 45 degrees, returned to upright, and
• The CO₂ scale is read.
  
  The typical Co2 Target is 12%

The Carbon Dioxide vs Oil Burner Efficiency chart below explains how the percent of carbon dioxide in oil burner exhaust gases translates into oil burner efficiency. Bachrach Fyrite instructions and Oil Burner efficiency chart below, source: Audel's Oil Burner Guide.

Relationship Between CO₂ level, O₂ level, Smoke, Test Results & Oil Burner Efficiency

CO₂ - O₂ Ratios: proper CO₂ or O₂ settings at the oil burner versus smoke test results

One of our readers, Robert, asked what was the relationship between the measured smoke level at an oil burner and the CO₂ leve.l

If my smoke level is zero what should my CO₂ level be?

If my smoke level is zero what should my CO₂ level be

Of I set the smoke test to 0/1 then when I adjust the air flow again for the CO₂ 11.5 and co at 5.5 will my smoke test figure not to up - On 2019-12-26 by Robert -

Our Reply

Although changing the combustion air volume will change the smoke level, the smoke level itself will not directly translate into a specific CO₂ level.

Typically, for a modern high speed oil burner burning No. 2 fuel oil, you'd set the flame to just a trace of smoke - that is barely above zero, less than 1 on the smoke scale - then you'd open the air shutter until you see 12.0% CO₂or 4.5% O₂.

Beckett points out that at that point if you check the smoke level again it ought to look like "zero" on the scale.

Take a look also at the stack temperature, oil burner fuel unit pressure level, nozzle size and spray pattern and how those match to the combustion chamber design, cleanliness of the heat exchanger and stack (sooty pushes up stack temperature), draft, etc.

Also, a nice summary of these settings is given by Beckett at

• PROPER OIL BURNER ADJUSTMENT [PDF] available here at InspectApedia.com, retrieved anew 2019/12/27, original source: R.W. Beckett Corporation, 38251 Center Ridge Rd, North Ridgeville, OH 44039 USA, Tel: (800) 645-2876 https://www.beckettcorp.com/support/tech-bulletins/proper-burner-adjustment/
  

Table of % CO2 in Flue Gas vs Oil Burner Efficiency

Oil Combustion Efficiency vs Stack Temperature at 12% CO2

The chart above illustrates combustion efficiency, stated as fuel loss at an oil burner, for a given CO₂ level at different stack temperatures.

[Click any image or table to see an enlarged, detailed version.]

Watch out: It's easy to make it look as if oil burner has been set for very high efficiency: just stand with your leg blocking the air intake at the oil burner air shutter while making the CO₂ measurement.

But that nonsense, while it may make the burner adjustment look "good" is likely to waste fuel during the heating season and may result in smoky sooty operation leading to a loss of heat.

We want good oil burner efficiency, up to the point of improper operation.

The illustrations at left and below, from our Bachrach manual, explain how the Fyrite CO₂ analyzer is operated and give a chart useful to read oil burner efficiency levels for different CO₂ levels at different operating temperatures.

Combustion Analyzer Recommendations & Sources of Oil or Gas Burner Combustion Testing Kits include CO₂ 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

UEI Eagle produces a range of test instruments used for heating system analysis and tuning.

Shown above, UEI Eagle test instruments, mounted magnetically to the service truck wall. These tools were used to measure the performance of an LP gas fired heating boiler in Two Harbors MN.

The second image above shows the Eagle test instrument report printed at the job site.

• UEI Eagle 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
  or
  
  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.

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.