ASHRAE Journal- September 2008

than other heating/cooling systems, they do have a high control performance. This Room is partly due to the small temperature Temperature difference between the room and the Sensor system (water, surface) and the resulting Moisture and high degree of self-control. Studies on Temperature Sensor controllability of ﬂoor heating/cooling show that ﬂoor heating controls the room temperature as well as radiators. To avoid condensation on a cooled surface, there is a need to include a limitation on water Main Control Unit Heating/Cooling TS TS temperature, based on the space dewOutdoor point temperature. HC Temperature Sensor A control concept for a combined ﬂoor M heating-cooling system is shown in Figure 3. For heating supply water temperature, M the average value of the supply and return M water temperature is controlled according to the outside temperature (ﬂux control TS = Maximum/Minimum Temperature Sensor M = Actuator at Three-Way Valve according to a preset heating curve). In HC = Heating/Cooling Control Unit M = Thermal Actuator addition, an individual room thermostat may control the water ﬂow rate to each Figure 3: Concept for the control of a combined ﬂoor heating and cooling system. room. This will typically be an on-off control. For ﬂoor cooling the supply water temperature or the Membrane Solar Reﬂection tair = 24°C average value of the supply and return water temperature is also 70% toperative = 27°C controlled according to the outside temperature (ﬂux control according to a preset cooling curve) with a limiter based on Fritted Glass the dew-point temperature in a reference room. In addition, an Low-e Absorption 28% Coating individual room control may be set to shut-off or open for the Solar Absorption water ﬂow to each room. Reﬂection 36.5% The heating and cooling curve give the relation between ﬂoor 60% system water temperature and outside temperature. This curve will depend on internal loads, type of building, and external Transmission climate. In the control concept shown in Figure 3, the three2% Reduced Longway valves ensure that the return water is going back to the Wave Radiation chiller, when in cooling mode, and back to the heater, when Transmission in heating mode. 3.5% Cooling Source As a ﬂoor system is a high-temperature cooling system, and a low-temperature heating system it provides the high efﬁciency of a heat pump. This can be an air/water, water/water, ground/water type or an absorption heat pump. As the ground temperature often is around 10°C, it is possible to cool a ﬂoor directly from a ground heat exchanger without the use of a heat pump. A ﬂoor cooling system may often be used together with a convective cooling system. Then, the ﬂoor system may take most of the sensible load, while the air system will take care of the latent load. At the same time, the dew point in the space will be lowered, and a higher cooling capacity of the ﬂoor system may be obtained. Another advantage is the high return water temperature from a ﬂoor system, 18°C to 20°C (64°F to 68°F), which will increase the efﬁciency of a chiller designed with a higher evaporator temperature. 20 ASHRAE Journal Supply Air 18°C, 4 ACH Floor Surface 21°C 13°C Floor Cooling 19°C Figure 4: Design concept for concourses at the new Bangkok Airport. Applications Floor cooling can be applied almost everywhere ﬂoor heating is applied (single-family homes, multifamily homes, ofﬁces, industrial buildings (hangars, storage spaces, large halls, etc.), museums, sports facilities, churches, etc. The system types are the same. Floor cooling is particularly efﬁcient in large spaces ashrae.org September 2008 http://ashrae.org

Table of Contents Feed for the Digital Edition of ASHRAE Journal- September 2008

ASHRAE Journal- September 2008 Section: Contents Contents Section: Commentary Options for Sustainability Section: Industry News The Silk Route for Energy Solar Thermal Is Unrealized Opportunity Industry Groups Sue City of Albuquerque Section: Letters Letters Section: Meetings and Shows Meetings and Shows Section: Feature Articles Article-Radiant Floor Cooling Systems Article-HVAC Design for Sustainable Lab Article-Mixed Mode Ventilation Article-Single- Design Considerations For Active Chilled Beams Article-Acoustic Design In Green Buildings Article-Teams, Contracts & BIM Section: Building Sciences Some Old Lessons Distilled Section: Washington Report Energy in Federal Buildings Section: Products HVAC&R Product Showplace Section: Emerging Technologies Toplighting & Lighting Controls For Commercial Buildings Section: Special Products Fans & Blowers Section: Classified Ads Classified Ads Section: Advertising Index Advertising Index

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