CDC 3E151: Volume 2. HVAC/R Fundamentals Questions with Certified Solutions

CDC 3E151: Volume 2. HVAC/R Fundamentals Questions with Certified Solutions (201) What affect will dust on fan blades have on heat transfer? It will reduce heat transfer (201) Where do you view the rotation and discharge of a centrifugal fan? On the drive side (201) Why are vanes used in the vane axial fan? To straighten out the spiraling motion of the air (201) What will allow a sheave to be used on different diameter shafts? Bushings (201) Where will the classic V-belts ( A through E ) be used? Medium horsepower applications (201) If you have four belts and one is bad, how many should you replace? 4 (202) In a single-duct unit, why is the manual damper left in its initial position? To maintain a constant airflow through the box (202) Which design(s) do multiple-path systems use? Separate cold- and warm-air duct distribution systems or separate supply duct to each zone (202) Why are multi-path, multi-zone systems limited to smaller areas? Because of the multiple runs of single-zone ducts (202) If a cooling demand is reduced in a building, what will the supply dampers do? Begin to close (202) What is one reason for the use of terminal reheat? Allow zone or space control for areas of unequal loading (202) What makes an independent variable air volume (VAV) system truly independent? They can control the maximum and minimum cfm that can be supplied from the box (203) How do you prevent carryover into the ductwork while using atomizing sprays? Using an eliminator or filter (203) When is the use of a return air system generally essential? On larger systems (203) What is the result of a dirty or clogged filter? Resistance to flow and reduced efficiency (203) What causes the adjacent blades on an opposed-blade damper to move in opposite directions? A linkage (204) What does carbon monoxide combine with no interfere with the oxygen supply? Hemoglobin (204) What will affect a person's sensitivity to an odor? Temperature and humidity (204) What can make locating an indoor air quality issue difficult? The different sensitivities of people (205) How can air be cleaned? By filtering the air and cleaning the ductwork (205) What should be considered while planning the ventilation for odor control? Increases in heat load and the availability of air of adequate quality (206) When would the greatest pump lift possible occur? If there were a perfect vacuum at the pump suction (206) What may cavitation cause? Pitting and wearing of the impeller (207) What should be done if a stuffing box leaks too much? Tighten the stuffing-box gland (207) A leaking seal is replaced when the fluid leakage rate exceeds 5 drops per minute (207) What should you check when you are making major repairs on a pump? The performance of the pump