Chilled ceilings are mounted within the ceiling to provide quiet, draft free cooling of the space below. Each unit is made up of a small bore chilled water pipe arranged in an S-shape and attached to the upper surface of a ceiling panel. Ceiling panels are typically of thin metallic construction but can simply be plasterboard. In some systems the chilled water pipes are embedded within the ceiling panel.
During operation, the panel is cooled through contact with the chilled-water pipework allowing it to cool the space through a combination of convective and radiant output (up to 40% radiant). An insulating mat is often placed above the chilled water pipework and panel to minimise uncontrolled cooling of the area above.
One advantage of chilled ceilings is that they can be placed in a shallow ceiling void enabling them to be used in buildings with low floor to ceiling heights. However, their limited cooling output makes them unsuitable for areas with moderate to high heat gains. The maximum capacity of chilled ceiling systems is in the order of 70 W/m2.
Chilled-ceiling systems require a separate ventilation system for fresh air supply.
Condensation of room air on and within the chilled ceiling can be avoided by shutting of chilled water flow based on room dew point temperature.
Two types of chilled ceiling are available in DesignBuilder HVAC:
Chilled ceilings will only control based on the radiant system controls defined for the component and not via a zone thermostat such as is used for forced air systems. If the radiant system is serving a zone with forced air equipment, the radiant system will follow the priority order established by the zone thermostat but will still base its response on the controls defined by the user for the radiant system.
Important Note: The ceiling constructions of zones in which chilled ceilings are to be positioned must have a special internal source construction which incorporates details of the embedded tubing system. See Internal Source under Constructions for further details.
Chilled ceilings are placed, edited and deleted at HVAC zone level.
To edit the data associated with a chilled ceiling, you first need to select it by moving the mouse cursor over it and then clicking the mouse button to select it. You can then access the edit dialog by right-clicking the mouse and selecting the Edit selected component option or alternatively, select the Edit selected component tool from the toolbar.
Tip: If your chilled ceiling model doesn't seem to be meeting cooling setpoints you should make a couple of checks. Firstly make sure that you remembered to include insulation in the chilled ceiling construction in the layer above the internal source (chilled water pipes). Omitting the insulation would cause leakage of cooling which would not have been accounted for in sizing calculations. Also check for excessive cooling loads in the space.
It is not usually possible to supply more than about 70 W/m2 with chilled ceilings.
When editing the attributes associated with a Chilled ceiling it is possible to apply the same changes to units in other zones in the same HVAC Zone group. To do this select the components on the Target tab of the edit dialog as required.