BOMI: AHU, Water Treatment and Plumbing Exam

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BOMI: AHU, Water Treatment and Plumbing Exam

Newest| Actual Exam with 150 Accurate Questions and Detailed Verified Answers (100% Correct Answers) Already Graded A+

Define relative humidity - ANSWER - RH (relative humidity) describes the amount of water vapor held in the air.

Does moist air have more or less density than dry air? - ANSWER - Moist air has less mass than dry air and is less dense than dry air.

What is pull-down load? - ANSWER - Heat left over from the day before must be removed the following morning when the air-conditioning system is restarted. The leftover heat is called the pull-down load and must be added to the instantaneous solar heat gain during the morning hours to determine the cooling load for the air-conditioning system.

How can the problem of air and water vapor infiltration into a building be solved? - ANSWER - To reduce these infiltration problems, ventilation air should be introduced through the air-conditioning system in constant quantities to maintain a slight positive pressure within the building. This pressure causes an outward escape of air through cracks, windows, and doors, limiting infiltration. In this way, the only outside air admitted into the building is that which has been cooled, dehumidified, and cleaned before being introduced into the occupied spaces.

Define absolute pressure - ANSWER - Gauge pressure plus standard pressure gives psia (pounds per square inch absolute), or absolute pressure. 1 / 3

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Define static pressure - ANSWER - Static pressure is generally used to describe duct pressure. Static pressure is the pressure of the air being pushed against the inside walls of a closed duct by the fan.

How is velocity pressure calculated? - ANSWER - To measure static pressure, a pitot tube partially filled with fluid is attached at a right angle to a long, straight length of duct. The air entering the tube from the duct will push the fluid inside the tube against the outside air that is used as a reference. The outside tubing allows a measure of the static pressure; the velocity pressure is eliminated from the reading. Velocity pressure is derived by subtracting static pressure from total pressure.

What is pressure drop? - ANSWER - The pressure drop is measured as the difference in pressure between where air enters a device and where it comes out of the device.

What is friction loss? - ANSWER - Friction loss is caused by air molecules slowing down by banging against the surface of the duct interior.

When designing a duct system, what is important to remember about directional changes? - ANSWER - The more changes of direction there are in the duct run, the less direct the airflow will be. Directional changes increase friction and reduce efficiency.

What is a problem with using fibrous glass wool as a ductwork material? - ANSWER - The World Health Organization has declared fibrous glass wool as "[possibly] carcinogenic to humans."

Which type of duct uses fiberglass insulation? - ANSWER - Fiberglass insulation is the primary material used to insulate flex duct. 2 / 3

pg. 3 How can duct leakage be eliminated? - ANSWER - Duct leakage can be eliminated through the use of sealants applied to all duct joints- duct collar tap-ins, branch intersections, access doors, and air terminal connections.

What are the main elements of good IAQ (indoor air quality)? - ANSWER - Acceptable temperature and RH (relative humidity), controlled airborne contaminants, and adequate distribution of ventilation air

What is the best type of environment for biological contaminants to thrive? - ANSWER - Biological contaminants thrive in areas that are dark, moist, and laden with nutrients.

What is the best way to control IAQ (indoor air quality)? - ANSWER - The primary purpose of ventilation is to control IAQ by diluting polluted indoor air with less contaminated outside fresh air. In many instances, ventilation air alone will reduce IAQ problems.

Generally, how long can a duct be before it needs to be insulated? - ANSWER - Generally, you should insulate if the duct is more than 50 feet long.

What determines the amount of ventilating air required in a building? - ANSWER - The amount of ventilating air required depends generally on the number of people occupying a space, their activities, the volume of the space, and the duration of the stay of the occupants in that space.

According to ASHRAE Standard 62-1989, how many cubic feet per minute of air exchange should maintain an acceptable IAQ (indoor air quality) level? - ANSWER - The air exchange rate should be 15 cfm per person to maintain acceptable indoor air quality in a reception area. In office space and conference rooms, the standard is 20 cfm per person.

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