How to use chilled beams.
Chilled beams are one of the many cooling methods that your HVAC professionals may recommend to clients. As a refresher, they can be active, passive, or multi-service.
Passive chilled beams do not rely on a primary air supply and instead use radiant convection to work. Active chilled beams use a direct air supply to create the induction they need. Multi-service chilled beams are active beams but have additional features, such as lighting, smoke detectors, or sprinklers. Most HVAC experts typically put multi-service and active chilled beams in a single category.
How chilled beams work.
The way that chilled beams work depends mostly on whether they are passive or active. The following figure shows the general structure and functionality of each type.
Passive chilled beams:
- Step 1: This type of chilled beam is made up of heat exchange in the fin-and-tube style within a casing and hanging from the ceiling.
- Step 2: Cold water travels through the tubes in the system.
- Step 3: Thanks to thermodynamics, the warm air in the room rises and moves towards the beams in the ceiling.
- Step 4: The cold water in the beams cools the air. This makes the air drop back down.
- Step 5: The result is the convective movement of the air that cools the space.
Active chilled beams:
- Step 1: The design of active chilled beams is similar to that of passive ones, but the housing can be suspended from the ceiling or recessed into it. As mentioned, the big difference is the integral air supply in active chilled beams.
- Step 2: The primary air supply moves through the system’s nozzles.
- Step 3: The nozzles induce the space’s air, driving it through the chilled beams’ cooling coil.
The induction process results in active chilled beams having larger cooling capacities compared to their passive counterparts.
The impact of chilled beams – pros and cons.
Chilled beam systems are commonly suggested in HVAC applications because of their range of advantages. Even so, there are a few disadvantages that you and your technicians should be aware of.
Minimal infrastructure on the air side.
You only need a central air system in the case of outdoor primary air. This means that chilled beams do not typically require a lot of infrastructure on the air side, reducing the square footage of floor space required.
Reduced ductwork requirements.
One of the most frequently-cited benefits of chilled beams is that they do not require ductwork that is as large as that needed for variable air volume systems. This is because chilled beams use induced airflow to cool some of the space. The reduced ductwork can even reduce the height between floors and the infrastructure needed.
For example, the following chart shows a situation in which active chilled beams would require 60 percent less primary airflow for the same space as a vav system.
No fan unit at the end.
Because chilled beams do not need a terminal unit fan, they have lower system fan energy requirements than other systems, such as fan-powered vav, doas, and four-pipe fine coil units.
The lack of terminal fans in chilled beam systems also means that they tend to be very quiet. This quiet operation is furthered by the fact that there are no compressors by the area that people will be in.
Even so, you should keep in mind that many vav systems are quiet, depending on their design and installation.
No condensate filters or pans.
Chilled beams also do not have any condensate filters or pans. This reduces the maintenance required compared to systems that do require this part.
The simplicity of the system for chilled beams is also a benefit, making the units easy to design and control. Some of the system’s simplicity comes from the already-mentioned lack of condensate pans and fans. The controls for both the ahu and the terminal units are also more straightforward than other systems.
More energy efficient.
From an environmental and financial perspective, one of the most significant advantages of active chilled beams is that they use less energy than vav systems. This comes from multiple factors, including:
- the lower primary airflow
- the improved chill efficiency thanks to the water temperature in the chilled beams
- the lack of reheating thanks to the cooling coils at zone levels
The following charts show an efficiency comparison:
The reduced costs of chilled beams start with installation. The lower floor-to-floor height reduces the cost of building the exterior wall. The smaller size of the beams also reduces the cost.
In most cases, chilled beams have lower running costs, saving your clients money in the long-run.
Some heating abilities.
The heating abilities of chilled beam systems are both positive and negative because they exist, but they are not enough for many situations. To take advantage of their ability to heat a space, you need to send hot water in the coils instead of cold water.
At least one beam required by room.
There must be at least one beam in every room to use chilled beams to cool multiple rooms. Some other solutions, like fan coil units, dedicated air system terminals outside, and terminals with variable air volumes, can cool multiple rooms.
Higher pumping energy required.
Compared to variable volume air systems or fan coil units, chilled beams tend to require more pumping energy. This comes from the fact that chilled beams usually have a lower delta-t on the water side, thanks to the need for that water to be slightly higher than the room’s dew point.
Requires an outdoor air unit to avoid condensation.
When chilled beams are used for cooling, they need an outdoor air unit dedicated to their use. That unit constantly gives the building spaces the ventilation air with the low dew point. Without this step, the humidity levels would rise, and there could be condensation by the chilled beams. That is important, as condensation could damage the finishes in the building and make the space uncomfortable.
You may need a separate heating system.
Although chilled beams can frequently be used for heating, this is not always the case. This is particularly true in climates that require more heating than cooling. It comes down to the fact that chilled beams rely on cold air’s density to create airflow, reducing their effectiveness at heating a room.
While some other cooling systems can incorporate particulate air filters, that is not the case with most chilled beam systems. This means that the system cannot filter out particles that people accidentally bring into space.
Water leaks can occur.
There is also a risk of leaking water with chilled beams because of the fact that they are water-based. To reduce the risk, you need to install control valves and piping, which can potentially increase installation costs. Of course, this would also be an issue in some vav systems, such as those relying on heating coils with hot water.
Whether discussing chilled beams or any other HVAC technology with your team, you need a reliable method of communication. Podium Teamchat can help with this, while Podium Videochat can make it easier to diagnose customer’s issues with chilled beams remotely, so your team knows what to bring to the site. Meanwhile, Reviews can help you gain valuable feedback from satisfied clients.