K-PLAN - 1 of 2 - Q & A - Building Systems
If a wall has a total thermal resistance R-25.4, the U-value of the wall is what? Give your answer with four decimal places.
0.0393. The U-value of an assembly is the reciprocal of the resistance. U = 1 divided by R. 1 divided by 25.4 = 0.0393.
If the public water service provides water at 100 psi, and there is a friction loss of 15 psi between the street and the building, what is the highest floor on which a faucet may be placed if the faucet requires 15 psi? Assume that each floor is 12 feet high.
13 stories. 100 minus 15 PSI for friction loss results in 85 PSI at the building. In order to obtain 15 PSI for the faucet, there can be a loss of no more than 70 PSI 85 - 15 = 70 PSI. 70 PSI x 2.3 feet per PSI = 161 feet. At 12 feet per story, the faucet may be located 13.4 floors above the ground
A large family room requires two light switches to control the same light fixture. What is the number and type of switches that should be provided?
2 three-way switches. When two light switches control the same fixture, each must be connected to the fixture and to each other-these are called three way switches.
What is the minimum required clear distance from the face of an electrical panel to the nearest obstruction?
36 inches of clear space must be maintained in front of an electrical panel to facilitate safe access and servicing.
What is a design day?
A design day is a day that is colder than 98 percent of the day's experienced in a given climate
Select the correct statement about mass walls from those that follow.
A mass wall is a solar design device that uses the mass of a material to absorb direct solar radiation. Mass walls operate on a cycle of storing and releasing heat. Mass walls utilize direct solar gain to heat buildings. Two types of mass walls are trombe and water walls.
To what height will 50 psi of pressure lift a 3-inch-diameter column of water?
A pressure of 1 pound per square inch, PSI. can lift a column of water 2.3 feet. Thus, 50 psi can lift water 50 x 2.3 = 115 feet. This is independent of the size of the pipe or column of water.
One of the least efficient hydronic systems is the single pipe (choice A). With only one pipe, supply and return water are mixed after passing through the first coil, and this reduces the temperature of the water supply for the remaining coils on the loop.
A two-pipe system (choice B) is more efficient than a single-pipe system because there are separate supply and return pipes, which allows each coil to receive water at the same temperature. Both the singlepipe and two-pipe systems are limited to heating only.
The comfort zone generally ranges from about 73°F to 77°F and between 20 percent and 60 percent relative humidity RH. If intake air in a system is 80°F and 10 percent RH, how should this air be treated so it will conform to comfort zone standards?
Add moisture to the air. the intake air is already lower in relative humidity than the comfort zone standards. If anything, moisture should be added to the intake air.
What is an economizer.
An economizer is an energy-saving strategy in which a part of the HVAC system is shut off while the rest remains in operation. This system utilizes cool outside water or air to minimize cooling costs when outdoor temperatures are low. The other devices listed are all part of the refrigeration cycle.
A Trombe wall is based on which of the following principles? The air between the glass layer and the mass wall only rises into the building when it is heated.
At night when it is cooled by losses to the outside, the air in the space sinks & pushes the lower duct flap shut, thus sealing the space from the building. The mass wall absorbs a great deal of radiation without a rapid increase in temperature & releases it again without a rapid drop in temperature
The heating and cooling capacities of a plant are measured in
BTUH & the cooling capacity is measured in tons. The U value is a measure of the insulating capacity of a wall roof or window. The plant has to be sized to take care of the load generated by gain or loss through the walls & other internal loads. But the U value is not a measure of the plant capacity
Double-glazing has a U-value of about 0.60, about half that of single-glazing. Triple-glazing has a U-value of about 0.40.
But the U-value of a solid wall is even lower-an insulated masonry or concrete wall has a U-value of around 0.10 to 0.20, which can be reduced to 0.04 or even less.
Traps are used to keep sewer gasses from entering the building. Valves are used to stop the flow of water.
Cleanouts are a segment of pipe that allows a snake to be inserted into the sanitary line to remove clogs.
Which among the following piping materials would satisfactorily serve a domestic water system? Copper. Lead. Cement-lined cast iron. Plastic. Galvanized steel. Aluminum.
Copper. Cement-lined cast iron. Plastic. and Galvanized Steel. Domestic water piping, which carries potable or drinking water, must be, most importantly, nontoxic. It must also be able to withstand high pressure, it must be easily connected with leak proof joints, and it must resist corrosion.
When is the solar load at its lowest in North America?
December 21 is the day of the winter solstice which is not only the shortest day of the year, but also the point during the year when the sun is at its lowest point in the sky. Consequently, the solar load on buildings is at its lowest on this day
A building's lighting system also produces heat. Reducing the lighting level, therefore, has two effects: in the summer, with less heat given off by the lighting, less cooling for the building is needed.
During the heating season, however, with the lighting system generating less heat, more heat must come from the building's regular heating system. So, reducing the lighting level in a building increases the amount of heating required and decreases the amount of cooling required for the building.
A vacuum breaker (C) is an automatic valve that admits atmospheric air into a supply pipe upon a reverse in flow. This causes the flow to stop, preventing hackflow and siphonage.
Finally, an air gap fitting (D) is a device that separates two drain pipes with an unobstructed vertical air path to the atmosphere. This ensures that backflow will not take place in the event a sudden pressure loss and momentary vacuum occur.
The presence of which of the following is considered Least harmful in a potable water supply? Carcinogens. High acidity. Fluorine. Magnesium
Fluorine. Fluorine (correct choice C) is often added to municipal water supplies to reduce the incidence of tooth decay. The benefits of fluoridation far outweigh the minor negative effects attributed to it.
Which of the all-water HVAC hydronic systems shown below is the most versatile and energy efficient?
Four pipe. The most versatile and energy efficient system is the four-pipe system, which allows simultaneous heating and cooling. With separate hot and cold water returns, the boiler and chiller require less energy than a three-pipe system to heat or chill the water.
Which of the following is not a backflow preventer? Double check valve. Gate valve. Vacuum breaker. Or Air gap fitting.
Gate valve. A gate valve is a manually actuated shutoff valve, consisting of a sliding plate or gate that is perpendicular to the flow. it is not a backflow preventer,
The National Electrical Code (NEC) contains regulations concerning the number and placement of receptacles in residential dwelling units. Which of the following is Not one of these regulations?
Hallways that are less than six feet long do not require receptacles.
Potable water, that is, water suitable for drinking, must be free of contaminants. Carcinogens, for example, are pollutants that contaminate underground water because hazardous chemicals have been improperly stored or discarded. Drinking such water increases one's risk of developing cancer.
High acidity rarely harms people but in time it will corrode pipes and require their replacement. Magnesium is a mineral that causes hard water, a condition that interferes with the sudsing action of soaps & leaves a mineral residue in pipes & hot water heaters that may interfere with a water system
Latent heat is d heat transferred when there is a change of state such as ice to water or water to vapor. Removing latent heat from the air, means removing water vapor from the air by changing it to water. However the intake air is already lower in relative humidity than d comfort zone standards
If anything, moisture should be added to the intake air. Sensible heat is the heat that changes the temperature, but does not add moisture or change the state of a substance. Removing sensible heat would bring the dry bulb temperature within the comfort zone
From the previous question, Which of the following are some of these regulations?
In any continuous length of wall, receptacles cannot be further apart than 12 feet. A required kitchen receptacle must not be higher than 18 inches above a countertop. Except in bathrooms, any wall at least two feet long must have a receptacle.
In an underground power district, the power company must provide service running underground to buildings.
In overhead districts, they only need to provide service overhead
An attached greenhouse solar system consists of a conventional greenhouse that is readily constructed on the south side of a structure, with a thermal mass storage wall separating the greenhouse from the rest of the building.
It is essentially a combination of direct & indirect gain systems. the greenhouse space is directly heated by sunlight, the back wall absorbs the heat & a portion of this heat is transferred into the bldg. The system differs from a thermal storage wall system, which is an indirect gain system
Which of the following best describes a two-pipe system?
It requires 1 pump only. It handles either hot water supply & return or chilled water supply & return. The single pump pumps the water either through a hot water boiler or a water chiller. Since only hot or chilled water is flowing, the building cannot be heated & cooled simultaneously
The body generates heat through metalbolic action, and this heat is released through radiation, conduction, convection, and latent heat. The first three processes depend on the temperature of the environment.
Latent heat transfer refers to the heat released by the evaporation of body moisture, through the lungs and through transpiration, sweating. The rate at which the moisture evaporates depends on how much moisture is already in the air, which is measured by the relative humidity.
Which of the following heat transfer processes are affected by relative humidity? Convection. Radiation. Latent heat. or Conduction.
Latent heat. Latent heat is the heat added to or removed from a substance when it changes state, for example the heat added to water, a liquid, when it becomes steam, a vapor. Latent heat is affected by humidity, and the greater the amount of moisture in the air, the greater the latent heat
Relative humidity is a comfort factor because of which of the following heat transfer processes? Radiation. Conduction. Convection. or Latent heat.
Latent heat. Latent heat transfer refers to the heat released by the evaporation of body moisture, through the lungs and through transpiration, sweating. The rate at which the moisture evaporates depends on how much moisture is already in the air, which is measured by the relative humidity.
Air filters include both disposable and cleanable types, and the electrostatic type is a particularly effective air cleaner.
Offensive odors are not easily controlled with filters, although activated charcoal filters are sometimes used for this purpose. Filters have no effect whatever on noise control, nor can they eliminate interior pollutants.
When performing cooling load calculations, heat generated by which of the following must be taken into account?
People, Lighting, Fixed equipment and Portable equipment. When performing heating load calculations, heat generated by people, lighting, and fixed and portable equipment must be taken into account.
Convection, radiation, and conduction are the three heat transfer methods by which heat flows from hotter to colder surfaces of objects. Convection occurs in a fluid medium, such as air or water, and is the process that causes hot air to rise.
Radiation transfers heat by electromagnetic waves, for example, the sun's rays that fall upon a surface. Conduction is the direct transfer of heat, such as the heat skin feels when you wash with hot water. These three methods of heat transfer occur without being affected by relative humidity.
You are the architect for a 100,000 square foot office building, and the owner has asked you to incorporate energy-conserving techniques into your design. For purposes of analysis, you have separated the building's energy-consuming components into six categories as follows:
Rank these categories according to their average energy consumption, from highest to lowest. Lighting. Heating. Cooling. HVAC fans. Vertical Transportation. Domestic Hot Water.
Which type of duct results in the least amount of friction loss?
Round duct. In comparison to the other choices listed, a round duct results in the least amount of friction loss due to the fact that the interior of a round duct has less surface area than a duct of another shape with the same cross-sectional area
The owners of a company have asked the design team to consider sustainability in the design of their new building. Which of the following site characteristics will have the Greatest impact on the building's mechanical systems?
Solar orientation. Solar radiation admitted through windows is among the highest sources of heat gain in buildings. Siting the building to limit this gain will have a significant impact on the overall size of the building's cooling plant.
regarding forced-air HVAC systems, Forced-air supply heated or cooled air efficiently by means of a fan and ductwork. By supplying more air than necessary, the building is positively pressurized, which eliminates infiltration.
Supply ducts can be noisy, especially near the HVAC unit, where fan and air-velocity noises are the greatest. Therefore, supply ducts are insulated on the inside for sound control, and they are also generally insulated on the outside for temperature control.
The R-value of a wall assembly is related to which of the following?
The R-value of a wall assembly is directly related to the sum of the R-value of the component parts. In addition, some amount of heat will transfer through the wall by materials that are in direct contact with each other.
The city of Columbus, Ohio, is located at 40 degrees north latitude. Using the solar plot provided, what is the sun's altitude and azimuth at 8 AM on April 1?
The altitude is 30 degrees and the azimuth is 80 degrees. Referring to the solar plot, find the curved line labeled with IV, which corresponds with the fourth month of the year, April and follow it to the point where it crosses the 8:00 AM or the number 8
All forced-air systems require fresh outside air to be mixed with return air to maintain the optimum number of air changes. The outside air must always be heated or cooled, while the return air will be closer to the required temperature.
The amount of outside air, however, should not be restricted simply because a harsh climate makes treating outside air more costly than in a more benign climate.
The Trombe wall system beneficial in any storage medium, since we do not want large and rapid temperature fluctuation within the living space of the building.
The mass wall causes a time delay when transferring heat into the building, allowing it to arrive at night, when it is most needed. In fact, concrete and stone have roughly a one-hour time delay per inch of thickness.
Which of the following represents a highly alkaline pH reading? 2, 7, 12 or 17.
The pH scale ranges from 1 to 14. Readings of 1 to 6.9 are acidic, a pH of 7 is neutral, and a pH from 7.1 to 14 is alkaline. Therefore a pH of 12 would he highly alkaline.
What is the definition of dew point?
The temperature at which the moisture contained in the air begins to condense. Air can hold more moisture when it is warm. If the air temperature drops below the temperature at which saturation occurs, the moisture will condense out. This results in either rain or dew.
This is why relative humidity is so important on hot days, when the other mechanisms are not working, or may even be adding heat to the body.
Then, the only mechanism able to remove heat is evaporation, which doesn't work very well if the humidity is too high.
The emissivity and ahsorptivity are often different between the infrared and visible spectrum. Selective surfaces are surfaces that have a high absorptivity in one wavelength (usually solar) and low emissivity in another, usually infrared.
This means that the material stores incoming solar radiation without releasing it as infrared (i.e., a good solar collector panel)
Some passive solar systems employ a conventional-type greenhouse that is attached to a structure. Which of the following statements about this system is incorrect?
This system is virtually the same as a thermal storage wall system.
Which of the following devices is used to prevent sewer gasses from backing up into the building? Arrestor. Valve. Trap. Stack.
Trap. The water that stays in a sanitary trap serves as a plug and keeps the methane gas from the sewers from rising into the building
Arrestors are used to prevent shock and quiet plumbing systems.
Valves are used to stop the flow of water. Stacks are vertical portions of a sanitary system, but do not prevent gasses from entering the building.
Which of the following systems can provide heating and cooling to different zones simultaneously?
Variable air volume, VAV, with electric reheat. It creates thermal changes by varying the flow of supply air into a conditioned space. Providing an electric reheat allows the temperature of the air to be increased at each mixing box, allowing the system to either heat or cool a given zone
Indoor air quality, IAQ, may be adversely affected by which of the following?
Ventilation rate. Smoking and Building materials. Indoor air quality (IAQ) may be adversely affected by building materials, ventilation, and smoking.
Air expands when it is heated, which reduces its density and makes it lighter. What is the only material that expands when it gets colder? Steel. Wood. Concrete or Water?
Water. The only material that expands when it gets colder is water. This fact necessitates careful construction detailing as water freezing inside joints will cause expansion and potential damage.
Conduction is the method of transferring heat through
a substance by passing from one particle to another.
In thermal storage wall systems, sunlight strikes the thermal mass wall where it is
absorbed by the mass, converted to thermal energy or heat and then transferred to the rest of the building.
In an overhead power district, the power company may provide service overhead and underground if the owner provides the conduit between the building and the power pole. In overhead districts, they only need to provide service overhead. However, if a building owner in
an overhead district desires underground service, the power company may elect to give him or her such service if the owner provides the underground conduit between the building and the power pole. The conduit needs to be encased in concrete only if the power is at a very high voltage.
Air filtration, which comprises an integral part of all HVAC systems, has as its principal purpose the elimination of
atmospheric particles. air filters prevent atmospheric dust, particles, and pollen from entering the HVAC system. As such, filters are generally placed where fresh air enters the heating, cooling, or humidifying equipment, so that it protects the equipment and promotes a more efficient operation.
Because the north and west sides of a building are often subject to cold winds, entrances on these sides should be
avoided if possible. it is generally true that the north and west sides of a building are most subject to cold winds
Sanitary waste can he treated in
cesspools or leach fields in remote sites, where no other treatment is available, although this is not a good solution in denser areas
The refrigeration cycle uses all of the following devices
compressor. evaporator coil. and condenser coil.
Candidates should have an understanding of some of the more common devices used in electrical work. A common light switch with two positions, on and off, is called a two-way switch. When two light switches control the same fixture, each must be
connected to the fixture and to each other-these are called three way switches. 2 two-way switches won't work since the switches cannot be connected to each other. There is no such thing as a one-way switch.
Convection is heat transfer by moving
currents of air or any other gas or liquid.
The amount by which the average outdoor temperature at a given location is below 65°F for one day is called a(
degree day. The amount by which the average outdoor temperature at a given location is below 65 degrees Fahrenheit for one day is called a degree day.
A device through which the air from a duct passes before entering a room is a diffuser. grille. turning vane. or damper.
diffuser. Many diffusers contain adjustable veins that allow for the redirection of air. Grilles are openings in the ceiling where return or exhaust air usually leaves a room. A turning vane is a device located within a duct that directs air around corners in ductwork.
The best method to reduce solar heat gain through windows is with the use of
exterior shutters. Because the object in reducing heat gain is to prevent solar energy from entering the building, it is always most effective to stop the radiation on the outside, before it reaches the glass.
A solar device consisting of either a parabolic trough or dish or an arrangement of lenses is a
focusing collector. A focusing collector consists of either a parabolic trough or a parabolic dish, or an arrangement of lenses, which focuses incoming light onto a tube or a point. It generates much higher energy densities and much higher temperatures than a flat plate collector
Evaporative coolers are inexpensive, relatively effective, and popular. However, they do not actually change the
heat content of the indoor air. They require a small amount of electricity to run a fan & a water supply to increase the relative humidity of the air supplied to a bldg. By increasing the relative humidity of a space, occupants feel cooler, although there is no change in the total heat of the air
An early example of passive solar heating is featured in a house designed by Frank Lloyd Wright near Madison, Wisconsin. Built in the mid 1940s, the project is known as the Solar Hemicycle house. Although displaying unusual energy awareness for its time, the design does Not take advantage of
high ceilings to promote convection for summer cooling. the ceilings in this house are fairly low. Cooling in the summer is achieved by overhangs that block the sun and by large door openings along the south elevation that allow breezes to pass freely through the building.
A device that is designed to prevent grease or oil from entering the sanitary system is called a: trap. interceptor. valve. cleanout.
interceptor. Interceptors are designed to prevent grease, hair, oil, etc., from getting into the sanitary system. They are required by code for certain establishments such as restaurants, which produce enough grease to create problems for the sewer system and treatment plant
Sanitary waste differs from water supply in that it
is usually in larger pipes than water supply. because it relies on gravity for its flow, rather than pressure, while water supply is pressurized
A material would make a good solar collection panel if it has
low emissivity in one wavelength and high absorptivity in another. The emissivity of a surface is a property of the material & is usually the same as the absorptivity at any given wavelength. Black surfaces heat up rapidly and cool off rapidly. Shiny surfaces heat up more slowly, hut stay hot longer
While a three-pipe system is less expensive to install than a four-pipe system, operating expenses are greater. The three-pipe system allows simultaneous heating and cooling by means of separate pipes to the hot and cold coils. The disadvantage of the system is that hot and cold water are
mixed in a single return pipe, producing water that is significantly different in temperature than the hot and cold return water leaving the coils prior to mixing. Therefore, the boiler and chiller consume more energy to heat or cool the water before it is pumped through the system again.
Building codes require that certain critical building elements have a fire-resistive rating. For example, an exit stairwell in a two-story office building of Type IV construction requires a minimum rating of
one hour. The purpose of all ratings is to assure that occupants will have sufficient time to exit the building in the event of a fire. Every component of the stairway enclosure must be rated one hour: the walls, doors, jambs, and all other openings.
The flow of electricity is affected by all of the following Except: potential. current. power. or resistance.
power. The flow of electricity is identified by Ohm's Law, which states that I = V/R, where I is the current, V is the potential, and R is resistance. Power is a measurement of work and is not a factor in the flow of electricity
Traps are provided in plumbing fixture drain lines in order to
prevent sewer gases from entering a building. A trap is a water seal fitting, often U-shaped, which is located in the drain line after the fixture. As it is filled with water, it forms a trap that prevents sewer gases and odors from reversing their flow and entering a building
The primary purpose of a plumbing fixture vent is to
prevent siphoning of the trap seal. the change in pressure within the pipe siphons the water out of the trap, rendering the trap ineffective. Therefore, the fixture vent was devised to equalize the pressure in the pipe. Air is drawn down the vent rather than water up from the trap
Heat transfers across a vacuum by means of, radiation. conduction. or convection.
radiation. In a vacuum, there is no medium available to conduct heat or to create convection. Ex. heat transfers across a vacuum, we receive heat from the sun across the vacuum of space. radiation is heat transfer in which heat travels rapidly in straight lines without heating the intervening space
Evaporative coolers, sometimes referred to as swamp coolers or desert coolers, are quite appropriate in hot, arid climates. Most evaporative coolers are roof mounted, where large quantities of hot, dry outdoor air are blown through pads kept moist by
recirculated water. The moist air is then delivered to the indoor space, where it cools the body and helps evaporation of body moisture. Evaporative coolers are quite effective in about half of the United States, from about the Midwest to the West Coast.
A square building will usually experience less heat gain or loss than a
rectangular building of equal area. The heat gain or loss of a building is a function of its surface area. Because a square building has less surface area than a rectangular building of equal floor area, it experiences less heat gain or loss
Doubleglazing reduces conduction gains and losses, but does very little to reduce solar radiation unless the glazing is
reflective.
The return duct of a centralized airconditioning system
returns the air from the air-conditioned rooms back to the central supply fan. The return duct provides the means of recirculating, returning, the room air back to the supply fan, to be cooled or heated as required.
Emergency exiting of handicapped people from the upper floors of a multistory building requires special consideration. For example, an appropriate method would be the use of
safe refuge areas within rated stairwells. Fire personnel are aware of these areas and will assist those persons needing to be rescued. Refuge areas must be located out of the direct exit pathway so as not to reduce the required exit width of the stairway
A backflow preventer is a plumbing device installed between potable and nonpotable water systems, which allows flow from the potable to nonpotable, but not in
the opposite direction. It often consists of two check valves in series (A) that allow the flow of fluid in only one direction. When the flow is reversed, the check valves are designed to close, thus preventing backflow.
Sanitary waste should not he mixed with storm drainage, because
the sewage treatment plant is limited in capacity, and adding the storm drainage would completely overwhelm the plant
The temperature gradient between the interior and exterior will have an effect on the amount of heat transferred, and thus the temperature on the interior surface. However the gradient does not affect
the wall's R-value, which is a constant regardless of temperature.
Four-way switches allow many switches to create a continuous series of circuit connections and are used when
three or more light switches control the same fixture.
Devices that change the voltage of an AC circuit to a higher or lower value are called
transformers. Transformers are called step up transformers when they increase the voltage and step down transformers when they decrease the voltage. While a transformer changes the voltage in a circuit, it has practically no affect on the total power in the circuit.
Venetian blinds and draperies can do little more than to
trap the heat against the glass once it enters the building. At that point, however, solar heat gain has penetrated the space.
Evaporative cooling is most appropriate in a climate that is
warm & dry. Evaporative coolers or swamp coolers, work by adding moisture to the air. A fan blows hot, dry outside air through pads that are kept moist by recirculated water. Although there is no change in the total heat content of the indoor air, relative humidity is increased & one feels cooler
