Division 5: Project Development & Documentation Flashcards
What are the five major variables that influence the space needed for mechanical equipment?
Scope of the system (local, centralized, or district), type of HVAC system, building size, building type, and passive systems use.
What is a local system in HVAC?
Generally, a system that only serves one zone, typically used for small buildings or for specific areas of a building.
What are some examples of a local system in HVAC?
A residential furnace, a window-mounted air conditioner, and commercial gas-fired heaters.
What is a centralized system in HVAC?
Generally, a system that serves multiple zones from one location, typically used in moderate- to large-sized commercial and institutional buildings.
What is a district system in HVAC?
Generally, a single plant that provides heating and/or cooling services to several buildings.
What are the three most common types of HVAC systems?
All-air, all-water, and air-water systems.
Which type of HVAC system requires the most space and why?
All-air system, because of the size of air handling units and the ductwork needed to distribute air throughout the building then return it to the central plant.
Which type of HVAC system requires the least space and why?
All-water system, because water pipes are smaller than air ducts and there are no supply air ducts.
Why do laboratories and hospitals generally need more mechanical equipment space than offices or apartments do?
Individual control is needed in many spaces and special provisions for ventilation and positive pressure are required in specific rooms.
In a medium- to large-sized building with an all-air or air-water system, what is the preliminary size range of the mechanical room?
3% to 10% of the total building area being served
In a medium- to large-sized building with an all-water system, what is the preliminary size range of the mechanical room?
1% to 3% of the total building area being served
What is an air handling unit (AHU)?
Mechanical equipment that uses water from boilers and chillers to heat and cool air
An air handling unit (AHU) is rarely purchased and placed as a ready-to-use assembly. True or false?
False
Why is it ideal to locate an air handling unit (AHU) near an exterior wall?
The amount of ductwork required to bring in fresh air and remove exhaust air is minimized
When locating a high rise building’s mechanical equipment, what are two factors to consider when deciding between the ground floor and the rooftop?
Structural requirements and noise control
Between round and rectangular ducts, which shape is better at maintaining air pressure?
Round
Between round and rectangular ducts, which shape is better at utilizing the available space?
Rectangular
What is static head (or static pressure) in HVAC?
The amount of pressure, measured in inches of water, that must be applied to overcome frictional resistance (between moving air and duct components) and make air flow
What is the preliminary cross-sectional area range for low-pressure duct space?
10 square ft to 20 square feet per 10,000 square feet of floor space served
What is a chase in HVAC?
A fully enclosed shaft that contains only ducts and piping
What is a mixing box in HVAC?
A component that controls the air that flows into a space from the main air supply line by adjusting quantity, velocity, temperature, and noise and is informed by signals from a thermostat
What are the size ranges of a mixing box in HVAC?
Height ranges from 6” to 18”, length ranges from 24” to 60”, and width ranges from 14” to 66”
What is a terminal reheat system?
An HVAC system in which the mixing box receives cool air at a fixed temperature, then heats it to the desired temperature, before distribution
What is a dual-duct system?
An HVAC system in which the mixing box receives cool and hot air from two separate ducts, then mixes them to reach the desired temperature, before distribution
What is a variable air volume (VAV) system?
An HVAC system in which the VAV box receives air at a fixed temperature, then varies the airflow rate as needed to maintain the desired temperature
What is access flooring?
A floor made of individual panels raised above the structural floor with pedestals to create usable space for running ducts and wires
What is a plenum?
The space between a suspended ceiling and the structural floor or roof above it
What are five systems that typically use a plenum?
Ductwork, sprinklers, plumbing, wiring, and recessed lighting
From top to bottom, what three system layers is a typical plenum divided into?
Ductwork, piping (sprinklers and plumbing), and recessed lighting
In commercial construction, the plenum is commonly used as a return air space. True or false?
True
When are exposed combustible materials prohibited within a plenum?
When it is being used as a return air space
What is the typical water pressure in city mains?
50 psi
What are the two primary types of water supply systems?
Upfeed and downfeed
What is an upfeed water supply system?
One which uses pressure in the water main to directly supply the fixtures
What is the range of the practical limit on building height with an upfeed system?
40’ to 60’
What is a downfeed water supply system?
One which pumps water from the main up to storage tanks near the top of the building, then supplies fixtures using gravity
What are four common materials that piping can be made of?
Copper, steel, plastic, and brass
What are four reasons that make copper the most commonly used piping material?
Corrosion resistance, strength, low friction loss, and small outside diameters
What are the three grades of copper pipes, from thickest to thinnest?
K, L, and M
What is cross-linked polyethylene (PEX)?
A relatively new material used in manufacturing flexible tubing that is suitable for hot and cold water supply lines under pressure
What is the primary advantage of using PEX pipes instead of copper or plastic pipes?
Environmental friendliness
In piping, what is a union?
A special fitting that connects two rigid sections of pipe and that can be easily unscrewed
In piping, what is a valve?
A mechanical device that controls water flow by opening or closing the passageway through a pipe
In piping, what is a gate valve?
A type of valve used where control needs to be either completely on or off
In piping, what is a globe valve?
A type of valve used where control needs to be variable
In piping, what is a check valve?
A type of valve that automatically restricts water flow to only one direction
In piping, what is an angle valve?
A type of valve with a single handle that controls both the hot and cold water supply and mixes the water to reach the desired temperature
What is water hammer?
The noise caused when a valve or faucet is closed quickly, causing water moving the system to stop abruptly and the pipes to rattle
How do you calculate the pressure loss from rises in elevation?
By multiplying the total rise in feet by 0.433 psi/ft
In plumbing, what is the demand load?
The flow rate that would be needed if every fixture in the system were in use at the same time
In plumbing, what is the probable demand?
The maximum flow rate that can be expected under typical conditions
What end value is considered when designing a water supply system?
Probable demand
What is a tensiometer?
An irrigation system device that measures the moisture content of soil at the plant’s root zone
What is a drip irrigation system?
One which slowly releases water at the soil level, only in the area of the plants, and can be controlled with timers and rain sensors
What are the two basic kinds of heating methods?
Direct and indirect
What is direct heating?
Heating water by bringing it into contact with surfaces heated by a flame, hot gases, electricity, or solar radiation
What basic kind of heating method does a typical residential tank-type water heater use?
Direct heating
What is indirect heating?
Heating water without bringing it into direct contact with hot surfaces, such as by using steam
What are the three basic types of heating systems?
Storage tank, tankless, and circulating
What is a storage tank heating system?
One which uses the same tank for both heating water and storing it for use
What is a tankless heating system?
One which quickly heats and delivers water as needed
What is a circulating heating system?
One which heats water in one tank then stores it in another tank until needed
What are the two types of drainage?
Sanitary and storm
What is sanitary drainage?
Drainage from food or human waste
What is storm drainage?
Runoff from roofs and landscaped areas
What is the two main reasons for considering the two types of drainage separately?
Sanitary drainage needs to be treated while storm drainage does not.
If sanitary and storm drainage were disposed of together, an unexpectedly large storm could overload the disposal system and cause sewage to back up into a building
What is blackwater?
Wastewater from toilets
What is graywater?
All wastewater that is not blackwater
Why is blackwater distinguished from graywater?
Graywater can be reused with little or no treatment for irrigation and flushing toilets, while blackwater would need more extensive treatment before reuse or disposal
