Combustion Analyzers
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 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.
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 analysis, and help on choosing which unit is right for your 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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