UNIT 51 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
51-1) List the four categories of gas fired furnaces based on flue gas temperature
51-2) Explain the difference between a Category I furnace and a Category IV
furnace?
51-3) List the five furnace cabinet configurations.
51-4) Why are standing pilot natural draft furnaces no longer manufactured?
51-5) What changes were made in furnace design to achieve 80% efficiency?
51-6) What is the difference between an 80% efficient furnace and a 90%
efficient furnace?
51-7) Discuss the evolution of the heat exchanger.
First heat exchangers were barrel shaped, then sectionalized were like
51-8) Discuss the operation of an atmospheric burner.
Gas leaves the burner orifice as a jet that enters in the center of the burner
51-9) Explain why furnace efficiencies jump from 80% to 90%
Efficiencies above 80% cause condensation either in the furnace or in the
51-10) What is the purpose of the orifice?
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The orifice meters the gas into the burner.
51-11) Why is it not a good idea to drill out orifices in the field?
51-12) What components are needed for a furnace to operate as a two stage
furnace?
51-13) Why are some condensate pumps not approved for furnace condensate?
51-14) Can the furnace drain and the air conditioning drain be run with a common
drain?
51-15) List the different types of gas burners.
51-16) Why do most furnaces today use in-shot burners?
51-17) What is the temperature rise of a furnace?
51-18) What part of the furnace does the air travel through first in all furnace
cabinet configurations?
51-19) Why should technicians be familiar with standing pilot, natural draft
furnaces since they are no longer manufactured?
51-20) Why are draft inducer fans necessary in today’s furnaces?