Oil burner carbon dioxide level testing, which in turn reflects combustion air & temperature adjustment is necessary for safe, efficient and reliable oil burner operation: this article explains and illustrates how an oil burner CO2 test is performed - a key step in oil burner adjustment.
We include charts showing the standard ratios or relations between an oil burner CO2 level (measured in the exhaust flue) and its O2 level, an alternative measurement of combustion quality.
An oil burner adjustment of combustion air, operating temperature, oil pressure, and other factors such as nozzle spray pattern selection all affect the completeness of combustion which in turn is reflected in the CO2 level measured in flue gas exhaust sampled in the breech. Page top image: the traditional Fyrite CO2 tester from a Bacharach oil burner tuning kit.
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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If the oil burner is not working, start your diagnosis
at OIL BURNER INSPECTION & REPAIR.
[Click to enlarge any image]
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.
Shown at left, a modern approach to measuring CO2 using the Fyrite II from 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 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.
The chart at left 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.
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. [Click to enlarge any image]
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.
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Below you will find questions and answers previously posted on this page at its page bottom reader comment box.
Robert
Although you're right that 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
On 2019-12-26 by Robert - 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
This Q&A were posted originally
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