User Manual

other imPortaNt faCtorS relatiNg to ComBuStioN
 •ThethreeT’sofcombustion
  –Time
 •Amountoftimethatthefuelandoxygenaretogetherinthecombustionchamber
  –Temperature
 •Howhighthetemperatureisdeterminestherateofoxidation,orspeedofthecombustion
  –Turbulence
 •Howwellthefuelandairaremixed
 •Thesethreefactorsareallinterrelated,andwillmoveyourresultsalongthecombustioncurves.
ComBuStioN meaSuremeNt termS
Other parameters measured include net temperature, draft and efficiency.
Net Temperature
Net temperature is the difference between the combustion air entering the combustion chamber and the flue gas tem-
perature past the heat exchange. This is used to determine how efficient the system is extracting heat from the combus-
tion process in addition to the performance of the combustion process. On sealed systems that have ducted inlet air for
combustion air, the net temperature must compare this air stream temperature with the flue gases. If the appliance simply
uses room air for the combustion air, our analyzers have an internal temperature sensor in the handset, so it will use this
temperature when calculating net temperature.
Themostaccurateresultsforefficiencyareobtainedwhenmeasuringfluegasesatthepointwherefluetemperature(not
flametemperature)isthehighest.
Draft
Draftisthedifferencebetweentheambientpressurelevelandthepressurelevelintheflue.Thisiscreatedeitherbythe
natural buoyancy of the hot gases created in combustion lifting, or by an inducer fan that assists the flow of flue gases up
thestack.Mostcombustionequipmentwillspecifytheamountofdraftthatisrequiredforproperoperation.
Drafthelpsdrawcombustionairintothecombustionchamber,andalsohelpsinmixingthefuelandoxygen.Without
proper draft, the combustion process can spill poisonous byproducts into the space where the appliance is located. This
canbearisktothoseinthearea,orcreateadangertoresidentsoremployeesworkingnearthecombustionequipment.
Efficiency
Efficiencyisameasureofhowwellthefuelisburnedtocreateheat,andhowwellthegeneratedheatiscapturedforthe
intended use.
The information used to create this value are based on the fuels heating value, the heat lost up the flue and the gas
components in the flue gas. The original method to determine efficiency included many manual methods and lookup
charts. As an example you would measure the CO2 level and the stack temperature and then reference a slide scale that
wouldgiveyoutherelativeefficiencynumber.UEi’selectroniccombustionanalyzersperformthemeasurementsona
continuous basis, and can calculate the efficiency as adjustments are being made. With this information you are able to
provideabeforeandaftercomparisonofthecombustionequipmentinrelativelylittletimeaspartofnormalservicing.
NOTE: Combustion analyzers measure the combustion efficiency. This is NOT the same as the AFUE indicated by the
manufacturer. The AFUE is derived through an extensive process, and includes many additional parameters such as start-up and
shut-down losses and shell losses as an example.
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