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Chilled beams are a type of convection HVAC system used to heat or cool rooms. Pipes containing hot or cold water are passed through the beam. As the beam heats or cools it radiates the warmth or coolness to the surrounding air.
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A chilled beam acts as a radiator chilled by recirculated water. The benefit of using a chilled beam system is that it eliminates fan energy and reliance on reheat. The warm air rises, is cooled by the chilled beam, and then falls back to the floor, where the cycle starts over.
Additional benefits of a chilled beam system include limited moving parts, quieter operation compared to VAV systems, and maximized space because chilled beams are installed overhead. Disadvantages include the development of condensation so the conditions much be kept within a certain range, more expensive than conventional systems, and difficult to install.
Types of Chilled Beams
They are available in three different variations: passive, active, and integrated/multi-service beams.
Passive - In a passive system there is no connection to an air supply source and it requires separate ventilation. It is primarily convective cooling and requires a dry atmosphere to prevent condensation. They rely on warm air rising, being cooled by the water-filled beams, and sinking again creating a convection air cycle. Chilled beam systems are made of copper tubing and bonded to aluminum fins. The system is housed in a sheet metal enclosure and mounted at ceiling level to provide convective cooling. Passive chilled beam systems are best used in spaces with light cooling loads.
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Active - In an active system, also known as an ABC system, the ventilation air is delivered to the beam by a central air-handling system via ductwork. It is also primarily convective cooling but its output is significantly higher than passive chilled beam systems. Active chilled beams are used for cooling and heating. They have very low acoustic signatures, and very high levels of occupant thermal comfort. This type of system is used in sound-sensitive applications such as libraries and hospitals as well as in retrofit applications since they require minimal overhead clearance. Due to the ABC system's superior energy efficiency and individual temperature control they are considered in LEED applications.
Integrated/multi-service beams - Multi-service beams include lighting, speakers, sprinkler openings, cable pathways, etc. They can be passive or active. Since they can include other building-service systems they are more expensive. Multi-service beams offer optimal fitting of many service systems so that installation is easier. Additional advantages of multi-service beams include: easily-accessible spaces for maintenance, more complex design requiring input from all planning teams, and reduction in time required to construct the building.
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The difference between passive and active beams revolves around the way airflow and fresh air are brought into the space.
Condensation can be a deterrent for installing chilled beam systems; however, with the proper controls in place condensation can be reduced or prevented.
By including an 'unoccupied' mode, setback temperatures and 'dry out' cycles can be implemented after long periods of unoccupied mode operation.
Dewpoint sensors are used to detect then disable the system when conditions are favorable for condensation. Moisture sensors can also be included.
The system can also include a switch that will disable the chilled beam in the event of a window opening, allowing the ambient conditions to produce condensation.
Chilled beam systems must adhere to certain standards to ensure proper design and functionality.
BRE IP11/04 - Passive chilled beams installed in the perimeter of buildings can be highly effective for off-setting direct solar gains and ensuring good thermal comfort in the perimeter zone. This paper presents the findings of a research project that has investigated the performance of perimeter chilled beams and developed guidance on avoiding the design pitfalls.
DIN EN 15116 - Ventilation in buildings - testing and rating of active chilled beams.