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UNIT 77 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
77-1) Although air handler cabinets may be made of galvanized steel, there are still areas
that may be subject to corrosion. Why?
77-2) Describe the two general types of AHU’s.
77-3) List the components of an FCU.
77-4) Often around fluorescent lights in a drop ceiling there is a narrow slit. What is the
purpose and advantages of application?
77-5) Where are larger FCU’s most commonly used?
77-6) In FCU’s that cooling coils, how is the dehumidification condensate disposed?
77-7) Explain the advantages unit ventilator type FCU’s have in schools.
A single unit ventilator is installed below window level in each classroom. An
77-8) List the major components in most AHU’s.
Heating and cooling coils
77-9) State the reason a properly sized AHU fan and motor usually requires field
adjustment during the final startup/commissioning phase.
77-10) Name the two basic types of fans used in most AHU’s.
77-11) On an AHU with a centrifugal fan, what are two advantages of backward curved
air foil blades?
77-12) State where axial fans are commonly used.
77-13) Tell why actual motor voltage and amperage should be field measured and logged
under full load conditions.
77-14) In a heating coil what advantage does heating water have over steam?
77-15) When referring to humidity, why is a cooling coil deeper (more rows) than a
heating coil?
77-16) How should ultraviolet germicidal lamps be handled?
77-17) Describe the problems associated with poorly maintained humidifiers.
Humidifiers that are not properly maintained are subject to mold and mildew
77-18) If the inside temperature is 70oF and the RH is 50%, how low would the outside
temperature have to be to form condensation on a double pane window?
77-19) Why is the steam grid humidifier recommended?
77-20) What horsepower motor will be required to increase the airflow of a fan to 1000
CFM if a ¼ horsepower motor is required to move 800 CFM?
77-21) What are the characteristics that AMCA fan classes are based on?
77-22) What are the two broad types of fan designs?
77-23) What is the difference in operating characteristics between centrifugal fans with
forward curved blades and centrifugal fans with backward curved blades?
77-24) Explain how a centrifugal fan moves air.
77-25) List the two main types of fan drives.
77-26) What speed does a fan need to turn to increase its airflow from 800 CFM to 1000
CFM if the original speed is 230 RPM?
77-27) What happens to the amp draw of a centrifugal blower motor if the airflow to the
blower is restricted?
77-28) What is an “air-over” motor?
77-29) What is the most common fan used in residential air conditioning?
77-30) Why should a current rating be taken any time a belt or pulley adjustment is made
to a belt drive fan?
