Choosing a combustion analyzer is one of the tougher pieces of test and measurement equipment for an energy auditor to choose. Electronic combustion analysis is a newer technology that is very often misunderstood, and the amount of information on individual units and applications is limited. Most information that is readily available is provided by the manufactures of the units, which is a bias source. With prices ranging from $450 to well over $5000, it is easy to get confused as to what features are important for an energy auditor and what features are overkill for your combustion analysis application.
Although not all of the below tested gases are required for current energy auditing standards, it is still important to note that compiling the most information available is a valuable asset to the energy auditor, the customer and ultimately the environment.
Dynamics that are frequently observed include, but are not limited to:
Oxygen - When O2 is present in the flue exhaust, surplus air was brought into the combustion process than was needed for complete combustion to take place. Excess O2 in the flue gas indicates that extra combustion air (Excess Air), was supplied to the combustion reaction.
Carbon Monoxide (CO) – Carbon monoxide (CO) is a extremely toxic gas that forms when too little air is drawn in to the burner. Throughout the combustion process CO2 is not completely formed (Ideal) due to the lack of oxygen, resulting in excess CO caused by oxygen forming with the carbon from the fuel.
Carbon Dioxide (CO2) – In a perfect combustion world, the supplied air would provide just enough O2 to react with the carbon in the fuel, to form CO2. The quantity of the delivered air is referred to as theoretical air. Although many combustion analyzers do not actually display Co2, it is still figured from other gas concentrations in a typical combustion analysis process.
Exhaust Gas Temperature - Heat leaving the exhaust flue with the hot gases is not transferred to do useful work. This heat loss becomes a major cause of lower fuel efficiency. The amount of heat (energy) of the exhaust gas is proportional to its temperature. Energy efficiency drops as the temperature rises.
Draft – Typically, measurement of draft is tested by calculating the pressure in the exhaust stack. Excessive draft can prevent heat transfer to the system, which leads to elevated flue temperatures. Low draft pressures can cause temperatures in the flue to decline, which can lead to water vapor condensing in the flue, developing acid and damaging the system.
Nitric Oxide (NO) & Nitrogen Dioxide (NO2) - Nitrogen oxides, including nitric oxide (NO) and nitrogen dioxide (NO2), are gases that lead to the development of acid rain, ozone and smog. NO gases are often pooled together and denoted as NOx. Testing of combustion analyzers has shown units that do not have NOx filtering of the flue gas before it hits the CO detector can have CO readings that are off by as much as 25%.
Sulfur Dioxide (SO2) – Sulfur dioxide is a corrosive and harmful to the environment. A sulfuric acid mist is formed when sulfur dioxide combines with water vapor in the exhaust flue. As a pollutant, sulfuric acid can be found in smog, fog, snow and acid rain. It is then transferred from those mediums to the soil, and eventually the ground water.
Another factor when choosing a combustion analyzer is cost of ownership. Calibration times depend vastly based on the amount of usage of the combustion analyzer. Although energy auditing is not a new industry, very recently energy auditing has seen vast growth and estimates on use of a combustion analyzer are generally related to usage in the HVAC business. Six months is a good guide line to use. Units that are from a design only a few years ago require the unit to be sent in for calibration. In addition to the expense of calibration the owner of the unit loses use of the unit for upwards of two weeks. Units were re-designed a couple of years ago and accept replacement cartridges in lieu of calibration. Cartridges range in price and cost should be known prior to buying a unit, as to figure cost of ownership over time. The most recent technology upgrade requires no cartridges or calibration and sensors that last upwards of five years for the the CO sensor, and 10 years on the O2 sensor.
For a free combustion analyzer evaluation, and help on choosing which unit is right for your combustion analysis business, please feel free to give us a call at 877-207-1244 or drop us a line via our contact us page.
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