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The nozzles through which primary air is supplied can produce noise. Thus, sound levels must be balanced with unit cooling capacity. Too much air can result in higher nozzle noise, but increased cooling capacity. Integration into the ceiling grid and coordination with lighting, piping, and other above-ceiling systems also are required.

The sizing of a chilled-beam system can be divided into four major steps:

1. Determine the load for the zone being served.

2. Decide on the preferred ventilation (primary) air, chilled-water, and hot-water supply temperatures and the maximum allowable pressure drop and noise at the induction nozzles.

3. Select the size and number of chilled beams for the zone.

4. If the number of chilled beams needs to be increased or decreased, revise the temperatures in Step 2 and repeat Step 3.

Dehumidification

Chilled-beam systems are appropriate in humid climates. The DOAS coupled with chilled beams are responsible for latent loads. In most cases, outside air is the largest latent load. The DOAS dehumidify outside air before it enters the building. If additional latent loads from the space need treatment, ventilation air that is dryer than the target space humidity can be delivered into the building.

To realize the energy-efficiency benefits of higher chilled-water temperatures in chilled beams, a direct-expansion compressor often is used in DOAS air handlers. Rumsey Engineers has found that over 80 percent of annual loads are sensible-cooling, not latent, loads.

The runaround coil is one strategy for reducing and even eliminating reheat energy in ventilation air and ultimately an entire chilled-beam system. This type of system puts a coil before and after the dehumidification coil in a DOAS air handler. In this configuration, some free precooling is harvested, and free reheat is realized.