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BOMI: Air Handling, Water
Treatment & Plumbing Systems exam
questions and answers 2025 /
BOMI - answer Air Handling, Water Treatment & Plumbing System Chapter 1 - answer Human Comfort Review Quiz 1 - answer 1 - The rate of exchange of fresh air for returned air in an air conditioning-system is based on the period of time covered and the number of building: - answer Occupants 2 - All of the 3 following are methods of heat - answer Radiation Convection Conduction NOT Reduction 3 - Which heat load source is most likely to affect all zones of a building? - answer Lighting equipment 4 - To compensate for heat gain from office equipment in modern office building, air- conditioning systems have been designed to offset how many watts per square foot? - answer 1 to 3 Watts per square foot. 5 - The leftover heat in a building from the day before is the: - answer Pull-down load
6 - What exists when the temperature and relative humidity of a person's environment permit the person to lose metabolic heat at the same rate he or she produces it? - answer Thermal comfort 7 - Why is it most important to air-condition with sedentary people? - answer They think about their comfort more 8 - How is sensible heat measured? - answer Dry-bulb thermometer 9 - What type of heat is released or used during a change of state between solid, liquid, and gas? - answer Latent heat 10 - Which of the following affects the amount of water vapor the atmosphere can hold? - answer Air temperature 11 - Which of the following is true about mechanical refrigeration cycle air flows? - answer Air flows from higher pressure to lower pressure 12 - Boyle's law states: - answer As Pressure goes up, volume goes down. 13 - Maintaining temperature and Blank have a direct impact on maintaining human comfort. - answer Humidity 14 - How does introducing air-conditioned and filtered air at a positive pressure into a building help building comfort? - answer It causes the outward escape of air, limiting infiltration. Chapter 1 Key Concept - answer 1 - What is the relationship between thermal comfort and metabolic heat? - answer Thermal comfort exists when the temperature and relative humidity of a persons
No change in state or physical property. 9 - Define latent heat - answer The energy that is used or released during the change in state. 10 - Define relative humidity - answer The amount of water vapor held in the air 11 - 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. 12 - What is the atmospheric pressure of air at sea level? - answer 14.7 psi 13 - Explain Charles' law: - answer Charles law explains why gases expand when heated and contract when cooled. 14 - Explain Boyle's law - answer Boyle's law states that a constant temperature, as the volume increases, the pressure decreases. 15 - How does the human body regulate temperature? - answer Sweating when overheating too cool down. 16 - What system produces the most heat in a building? - answer Zoning HVAC system? Maybe look into this one. 17 - What are the four main categories of internal heat loads? - answer People Heat Load Lighting Heat Load Equipment Heat Load System Heat Load
18 - How have office building HVAC systems been designed to compensate for heat gain from office equipment? - answer Air conditioning systems have been designed to offset one to three watts per square foot. 19 - 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. 20 - How can the problem of air and water vapor infiltration into a building be solved? - answer To reduce infiltration problems, ventilation air should be introduced through the air conditioning system in constant quantities to maintain a slight positive pressure within the building. The pressure cases an outward escape of air through cracks, windows, and doors, limiting infiltration. Chapter 2 - answer Air Properties and Heat Doctor Review Quiz 2 - answer 1 - Absolute pressure is equal to standard sea-level plus: - answer Gauge pressure 2 - It is unusual for an air-conditioning system to exceed how many p.s.i.g or p.s.i.a? - answer 0.5 psig 3 - The pressure of the air being pushed against the inside walls of a closed duct by a fan is called: - answer Static pressure 4 - The pressure that is created when air moved is called: - answer Velocity pressure 5 - Velocity pressure is found by subtracting: - answer Static pressure from total pressure
15 - What is a key aspect of a well-designed air-distribution service? - answer Maintaining air outlet noise below an objectionable level. 16 - Anti-smudge rings will help reduce deposit on outlets, but the best solution is to: - answer Select outlets with lower velocities 17 - Complying with codes regarding fire dampers help to: - answer Prevent facilities from smoke inhalation 18 - All of the following are commonly used methods of alleviating noise and vibration issues with equipment: - answer Housekeeping pads Vibration isolators Inertia bases NOT Fan cancelers Chapter 2 Key Concept - answer 1 - Define absolute pressure - answer The total pressure that is exerted on a gas or liquid from all sources, including the atmospheric pressure. Expressed in psia Absolute pressure (psia) is equal to the sum of the atmospheric pressure and gauge pressure. 2 - Define static pressure - answer The pressure of the air being pushed against the inside walls of a closed duct by the fan. 3 - How is velocity pressure calculated? - answer VP = SP - TP
The total pressure is a combination of static air pressure and velocity pressure. TP = SP + VP 4 - What is pressure drop? - answer Load is the resistance that a system must overcome to accomplish the job it was designed to do. A load cases a drop in pressure. The pressure drop is measured as the difference in pressure between where air enters a device and where is comes out of a device. 5 - What is friction loss? - answer Friction loss describes the relationship between the roughness of the duct interior surface and the velocity of the airflow in the duct. 6 - When designing a duct system, what is important to remember about directional changes? - answer Directional changes increase friction and reduce efficiency. 7 - What are the commonly used methods for air duct design? - answer Perimeter loop Extended plenum Perimeter radial 8 - Describe a perimeter loop system: - answer The supply duct is installed in a continuous, closed loop around the perimeter of the building. Ideal for single-story buildings with concrete slab floors where the ducts are sometimes cast into the slabs. 9 - What is a problem with using fibrous glass wool as duct-work material? - answer The World Health Organization has declared fibrous glass wool as carcinogenic to humans. Cannot use it in hospitals or kitchens. This type of material is used in low-pressure and low velocity duct systems. They have high friction.
Air velocity over 50 fpm is generally considered to be a draft. Air should be distributed betweem 25-50 fpm. 17 - What is short cycling? - answer Locating supply air devices and return air devices in close proximity to each other will cause short cycling. This results when the conditioned air flows directly from the supply device t the return deice without the conditioned air getting mixed within the room air. 18 - Describe air distributing ceilings - answer Air distributing ceilings are use of the confined space above the ceiling as a supply air plenum. This supply air plenum receives the conditioned air directly from the air handling unit with a minimal supply air duct system consisting of a short main duct and no branch ducts. 19 - What are dampers? - answer Airflow in the duct system is controlled by volume dampers. 20 - What are some characteristics of volume or balancing dampers? - answer The dampers provide a resistance to airflow to adjust how much air flows to various areas. Dampers are installed in each branch duct to ballace the quantity of airflow in the duct system. Volume dampers are also called balancing dampers. 21 - Why are fire dampers important? - answer Fire dampers must be installed between walls in the ducts to maintain seperation of one tenants pace from another. Fire damper prevents the spread of fire and smoke from one area to another through a duct system.
22 - What is a silencer? - answer A silencer is a specially designed duct component that changes airflow characteristics so as to reduce the noise made in the duct. Chapter 3 - answer Air-Handling Units, Fans, and Building Pressurization Review Quiz 3 - answer 1 - For a centrifugal fan, which type of fan blade affords a wider range of efficiencies and lower noise levels? - answer Airfoil 2 - The amount of work a fan performs to move a specific volume of air at a specific speed is called what? - answer AHP - Air Horse Power 3 - The amount of physical work that was input to a fan's motor to drive the fan shaft is called what? - answer BHP - Breaking Horse Power 4 - The air pressure a fan exerts in all directions against the inside walls of a closed system is called? - answer Static pressure 5 - A centrifugal fan delivers 6,000 cfm at a static pressure of 1.0 in. wg when operating at a speed of 400 rpm, and required an input of 3hp. If 9,000 cfm is desired from the same fan, what will the new speed be? - answer 60 0 rpm 6 - All 3 of the following are means to provide static pressure control of a centrifugal fan in a VAV system: - answer Vortex or inlet vanes Fan speed control Variable pitch blade control NOT Barometric Relief
The mixing box is a section of the air- handling unit where return building air mixes with fresh outside air 2 - What type of filter is most commonly available and is relatively inexpensive? - answer Pleated filters 3 - What are the most common fans used for air-conditioning and ventilation systems? - answer The axial and centrifugal fan is the primary fan used for supply and return air buildings. 4 - What are the advantages of an airfoil fan blade? - answer The airfoil design of the blades result in a smooth flow of air across the blade surfaces, eliminated eddy currents that produce turbulence and noise in the fan wheel. The use of airfoil blades affords a wider range of efficiencies and lower noise levels in fans. 5 - Define APH - Air Horsepower - answer The amount of work a fan performs to move a specific volume of air at a specific speed. What is BHP Breaking horsepower? - answer The amount of physical work that is put into the fans motor to drive the fans shaft. 6 - Define mechanical efficiency - answer The ratio of a Fan's AHP to it's BHP. this value stays the same through all of a Fan's different operating speeds. because of friction and turbulence loss in the fan itself, BHP is always greater than AHP. 7 - What do the basic fan laws depend on? - answer The basic fan laws depend on the fact that be Mechanical Energy of a fan remains constant throughout its use of range and operating speeds. 8 - What can the fan laws be used to determine? - answer These found laws can be used to calculate fan speed, horsepower, and system pressure as the volume of air moved by the fan varies.
9 - What is the formula for calculating a new fan speed in revolutions per minute? - answer New RPM = Old Rpm x (new cfm/oldcfl) 10 - What does a fan's system resistance curve represent, and what can you locate by superimposing the fan performance curve on the system resistance curve? - answer The system resistance curve represents the total resistance of the system. By superimposing the fan performance curve on the system resistance curve, you can locate the point at which this fan and this system will operate. What are three methods of static pressure control most commonly used for a centrifugal van in a VAV system? - answer The three methods of static pressure control most commonly used for a centrifugal van in a VAV system are: Vortex aka. inlet vanes Fan speed control Variable pitch blade control 12 - What is the most common cause of reduced fan performance? - answer Poor inlet conditions are the most common cause of reduced fan performance. 13 - Define building pressurization - answer Building pressurization is the measured difference in static pressure between the inside and outside of the building. 14 - How do most buildings reduce infiltration and control and monitor ventilation rates? - answer By maintaining positive pressure. 15 - What problem can develop when reducing the amount of ventilation air being brought into a building? - answer Problems with indoor air quality.
False:
- They do not require a filter o protect the evaporator coil from dirt and debris
- The suction line does not require insulation to prevent sweating
- When make up air is used, the coil is often subject to freezing 5 - Which is the best definition of a thermal zone? - answer A group of areas that act in a similar fashion over time 6 - An induction unit operates by supplying a constant volume of conditioned air through high-pressure nozzles located: - answer In the unit 7 - Which of the following is false about package units - answer They do not include a tube-in-a-shell or tube-in-a-tube condenser True things about packaged units:
- They require more maintenance
- They include a compressor, evaporator, a metering device, and a fan motor.
- They are dependent on proper chemical control of the water side of the unit. Key Concept Chapter 4 - answer 1 - What are four basic groups of refrigerants? - answer CFCs - Chlorofluorocarbons HCFCs - Hydrochlorofluorocarbons HFCs - Hydrofluorocarbons Ammonia
2 - What happens to a substance as it evaporates? - answer When a substance evaporates, it absorbs heat from its surroundings. 3 - What happens to a substance as it condenses? - answer When a substance condenses, it releases heat to its surroundings 4 - What happens to a substance's boiling point as the pressure is lowered? - answer Pressure can be used to manipulate the temperature at which a substance changes state. Reducing pressure of a substance can lower the boiling point. 5 - What is the purpose of the compressor? - answer The compressor is the heart of the refrigeration system. It creates the differential pressures that push and pull the refrigerant through the system. 6 - What is the purpose of raising the pressure by the compressor? - answer The compressor superheats the cool refrigerant gas thereby raising the pressure. 7 - How does the condenser operate? - answer The compressor sends high-pressure gas to the condenser, or outdoor coil where the refrigerants heat is expelled to the outdoors. When the hot gaseous refrigerant passes through a medium aka air or water, that is cooler than it is, the refrigerant condenses to a liquid, giving up its heat to the surrounding air or water. 8 - What is the purpose of a metering device aka expansion valve? - answer The condensed liquid then flows through the metering device. Located near the evaporator, creates a mist of small liquid droplets by forcing liquid refrigerant through a small opening. When it is atomized, the liquid's volume is increased, its pressure is reduced, and its boiling point is lowered. The expansion device sends refrigerant mist to a heat exchanging device called the evaporator. 9 - Briefly describe a split system - answer When the compressor is located in the condenser housing
15 - In an induction unit, where does the conditioned air and room air get mixed? - answer The air mixing takes place in the unit, which is either in the occupied space or ceiling plenum where a horizontal ceiling unit would be used. Chapter 5 - answer Indoor Air Quality Review Quiz 5 - answer 1 - IAQ is best controlled by diluting polluted indoor air with less contaminated fresh air in a process called: - answer Ventilation 2 - The ventilation required in a building varies with the: - answer Number of people and size of the space 3 - The three basic types of contaminants include all of the following except: - answer Viscous films. The three basic types of contaminates are:
- Solid & Liquid partials
- Gases and vapors
- Bacteria 4 - The type of filter that can remove vapors and odors is: - answer Activated charcoal 5 - A common method for detecting the existence of microbiological contaminants is: - answer Air sampling 6 - When carbon dioxide levels exceed Blank PPM, the efficiency of the ventilation system needs to be examined. - answer 1,000 ppm
7 - The term that refers to diagnosed illness such as allergies or infections that can be directly attributed to environmental agents in the air is: - answer BRI - Building related illness 8 - Which of the following is not an aspect of good indoor air quality? - answer Ventilation noise control The following are good:
- Acceptable temperature and humidity
- Controlled airborne contaminates
- Adequate distribution of ventilation air 9 - Under what conditions is a viscous impingement filter the best choice? - answer Where there is heavy dust concentration 10 - All of the following are examples of air contaminants except: - answer Oxygen Examples of air contaminants:
- Partials
- Mold
- Formaldehyde 11 - Why are open-filter media and filters placed so they are perpendicular to the main airflow direction? - answer To ensure the velocity through the filter media is equal to the dust velocity 12 - Which type of fibrous air filters use compressible panel-type glass or polymer fiber? - answer Roll filters
