Building Systems Flashcards
varies the quantity of air; One duct leads in and one or more lead out and is attached to registers mounted in the ceiling; cannot heat one zone while cooling another; low initial cost and low energy use
VAV (variable air volume) box (AAS)
4 parts of cooling systems
evaporator, compressor, condenser, expansion valve
A one-zone system. A separate supply duct and air-handling unit are required for each zone. This system is used for small or medium-sized buildings with few zones.
single-duct system with constant air volume (CAV) (AAS)
System has terminal reheat boxes that reheat previously cooled air. The zone with the greatest cooling load determines how much air is cooled for the entire building.
terminal reheat system (CAV) (AAS)
Terminal reheat box also controls air volume. Varying the volume of the supply air manages the temperature. The reheat function is used only when some space needs heating while the others all need cooling.
Terminal reheat system (VAV) (AAS)
Every zone receives air at the required temperature through a separate duct. Custom-mixes hot and cold air for each zone—thermostats in each zone control motorized dampers in the air-handling unit.
multizone system (AAS)
mixes hot and cold air to achieve the required air temperature. Mixing boxes are located throughout the building instead of a central unit. There is no limit to the number of zones possible. Two sets of large supply ducts are necessary. Costly, not energy efficient and require more building space.
double-duct system (AAS)
4 parts of water-based cooling systems
cooling towers, condenser water pumps, reservoirs of cooling fluid, make-up water pumps
most appropriate when large amount of ventilation is unnecessary or windows can be opened
all-water system
Consists of a fan and a coil in which water circulates. These units are often in cabinets placed under windows. The fan blows room air across coils through which either hot or cold water circulates. Thermostatic valves regulate the flow of water through the coils.
fan-coil system (AWS)
Each zone is heated or cooled by a separate water-to-air heat pump with this system. This system is most appropriate where simultaneous heating of some zones and cooling of others is required.
water-loop heat-pump system (AWS)
Usually located under windows. They use water for heating or cooling and neutralize heat gain or loss through the building envelope. A small amount of high-velocity air provides ventilation and air movement.
induction system (CS)
This type of system cools the ceiling. It cools large areas and distributes the cooled air throughout the space.
radiant panels with supplementary air (CS)
There is an all-air system for ventilation and cooling of the interior areas. Fan coil units around the building perimeter neutralize heat gain or loss.
fan-coil with supplementary air (CS)
Cool by convection. Can be recessed in a suspended ceiling or hang free. They can also incorporate lighting, sensors, and sprinklers.
Active chilled beams (CS)
How are duct sizes labeled?
W x H
Space required for air handler
minimum 2’x2’ or 2’x4’ access panel located directly below or adjacent to the unit
4 causes of poor IAQ
contaminants from indoor & outdoor sources, biological contaminants, and poor ventilation
If health symptoms can’t be traced to a particular source but disappear after the occupant leaves the building.
sick building syndrome
If health symptoms are linked to a particular building contaminant. In this case, symptoms don’t resolve after leaving the building, as with Legionnaires’ disease.
building related illness
This condition is caused by exposure to chemical contaminants. Long-term sensitivity may recur with each exposure to the chemical.
multiple chemical sensitivity
In cooler climates, the HVAC system can employ ___________ to capture exhausted heated air and return that energy to augment the building’s heating system.
energy recovery vents
An ___ can be subdivided into as many individually controlled areas as needed.
all-air
Which of the following is an air distribution system in which supply air originates at floor level and rises to return air grilles in the ceiling?
displacement ventilation
Preferred for projects with poor quality makeup water or in areas with higher water costs. These systems need access to fresh air, resulting in more space to house them. The main disadvantages are the bulky ductwork and the considerable fan power required.
All-air systems
This increases the complexity of the mechanical systems but decreases the size of the equipment. Air is supplied for ventilation.
combination system
Work purely by natural convection. Can only cool. Takes more of them to cool an area because of the slow motion of natural convection.
passive chilled beams (AWS)
