ASHRAE Journal - January 2013 - 42

lation system continued to operate, with all valves opening more often as the system attempted to maintain floor setpoints in the slowly cooling slabs. Conditions remained uniform throughout the building as it slowly cooled. As the air temperature dropped into the mid 60s (16°C to 18°C) more than a week after the estimated time of failure, an investigation revealed the inoperative valve.

Ground Coupled Heat Exchange With Thermally Active Slabs
Thermally active structures are particularly synergistic with ground coupled heat exchange systems. The cool chilled water and warm water required by thermally active structures can be supplied very efficiently with heat pumps using ground coupled heat exchange. The SAP Americas Expansion building in New Town Square, Pa., (Photo 3) and the National Rural Utilities Cooperative Finance Corporation Headquarters in Herndon, Va., use this technology to condition large atrium spaces. Both buildings use a closed loop well field connected to a water-to-water heat pump system to provide cool and warm water for the thermally active floor in the atrium. A dedicated outdoor air system provides ventilation, dehumidification and supplemental cooling to the atrium space. The air system has a

return air connection to the space for morning or overnight dehumidification. The floor system is controlled as a slave to the air system, operating only when the air system is at more than 40% heating or more than 40% cooling. A diagram of the system for the SAP Headquarters is shown in Figure 3 showing the dedicated outdoor air system and the thermally active floor that is connected to a ground coupled water-to-water heat pump. Heating/cooling changeover is accomplished at the heat pump itself. In some climates, anti-freeze may be required for the ground loop. Propylene glycol is often used for antifreeze in closed loop ground coupled systems, because it does not present the environmental hazards of ethylene glycol. It does have the disadvantages of increasing the viscosity of the circulating fluid at low temperatures and decreasing the specific heat of the fluid, resulting in higher pumping energy. For these reasons, propylene glycol is undesirable in the slab loop. Using denatured ethanol as an antifreeze agent avoids the viscosity and specific heat issues. The major disadvantage of this product is that in its pure form it is highly flammable, requiring special storage provisions. Storage of the material as a 50% water solution overcomes this problem, rendering the fluid no more hazardous than other commonly stored materials.

www.info.hotims.com/44628-184

www.info.hotims.com/44628-185

42

ASHRAE Journal

January 2013



ASHRAE Journal - January 2013

Table of Contents for the Digital Edition of ASHRAE Journal - January 2013

ASHRAE Journal - January 2013
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Long-Term Commercial GSHP Performance: Part 6: Maintenance and Controls
Thermally Active Floors, Part 1
Technology Award Case Studies:
Aquathermal Systems
Standing Columns
Data Centers
People
Emerging Technologies
IAQ Applications
Engineer's Notebook
Washington Report
Refrigeration Applications
Classified Advertising
Advertisers Index
ASHRAE Journal - January 2013 - ASHRAE Journal - January 2013
ASHRAE Journal - January 2013 - Cover2
ASHRAE Journal - January 2013 - 1
ASHRAE Journal - January 2013 - 2
ASHRAE Journal - January 2013 - Contents
ASHRAE Journal - January 2013 - Commentary
ASHRAE Journal - January 2013 - 5
ASHRAE Journal - January 2013 - Industry News
ASHRAE Journal - January 2013 - 7
ASHRAE Journal - January 2013 - 8
ASHRAE Journal - January 2013 - 9
ASHRAE Journal - January 2013 - 10
ASHRAE Journal - January 2013 - 11
ASHRAE Journal - January 2013 - 12
ASHRAE Journal - January 2013 - 13
ASHRAE Journal - January 2013 - 14
ASHRAE Journal - January 2013 - 15
ASHRAE Journal - January 2013 - Letters
ASHRAE Journal - January 2013 - 17
ASHRAE Journal - January 2013 - Meetings and Shows
ASHRAE Journal - January 2013 - 19
ASHRAE Journal - January 2013 - 20
ASHRAE Journal - January 2013 - 21
ASHRAE Journal - January 2013 - 22
ASHRAE Journal - January 2013 - 23
ASHRAE Journal - January 2013 - Long-Term Commercial GSHP Performance: Part 6: Maintenance and Controls
ASHRAE Journal - January 2013 - 25
ASHRAE Journal - January 2013 - 26
ASHRAE Journal - January 2013 - 27
ASHRAE Journal - January 2013 - 28
ASHRAE Journal - January 2013 - 29
ASHRAE Journal - January 2013 - 30
ASHRAE Journal - January 2013 - 31
ASHRAE Journal - January 2013 - Thermally Active Floors, Part 1
ASHRAE Journal - January 2013 - 33
ASHRAE Journal - January 2013 - 34
ASHRAE Journal - January 2013 - 35
ASHRAE Journal - January 2013 - 36
ASHRAE Journal - January 2013 - 37
ASHRAE Journal - January 2013 - 38
ASHRAE Journal - January 2013 - 39
ASHRAE Journal - January 2013 - 40
ASHRAE Journal - January 2013 - 41
ASHRAE Journal - January 2013 - 42
ASHRAE Journal - January 2013 - 43
ASHRAE Journal - January 2013 - 44
ASHRAE Journal - January 2013 - 45
ASHRAE Journal - January 2013 - 46
ASHRAE Journal - January 2013 - 47
ASHRAE Journal - January 2013 - Aquathermal Systems
ASHRAE Journal - January 2013 - 49
ASHRAE Journal - January 2013 - 50
ASHRAE Journal - January 2013 - 51
ASHRAE Journal - January 2013 - 52
ASHRAE Journal - January 2013 - 53
ASHRAE Journal - January 2013 - 54
ASHRAE Journal - January 2013 - 55
ASHRAE Journal - January 2013 - 56
ASHRAE Journal - January 2013 - 57
ASHRAE Journal - January 2013 - 58
ASHRAE Journal - January 2013 - 59
ASHRAE Journal - January 2013 - 60
ASHRAE Journal - January 2013 - Data Centers
ASHRAE Journal - January 2013 - 62
ASHRAE Journal - January 2013 - 63
ASHRAE Journal - January 2013 - People
ASHRAE Journal - January 2013 - Emerging Technologies
ASHRAE Journal - January 2013 - 66
ASHRAE Journal - January 2013 - 67
ASHRAE Journal - January 2013 - IAQ Applications
ASHRAE Journal - January 2013 - 69
ASHRAE Journal - January 2013 - 70
ASHRAE Journal - January 2013 - 71
ASHRAE Journal - January 2013 - Engineer's Notebook
ASHRAE Journal - January 2013 - 73
ASHRAE Journal - January 2013 - 74
ASHRAE Journal - January 2013 - 75
ASHRAE Journal - January 2013 - Washington Report
ASHRAE Journal - January 2013 - Refrigeration Applications
ASHRAE Journal - January 2013 - Classified Advertising
ASHRAE Journal - January 2013 - Advertisers Index
ASHRAE Journal - January 2013 - 80
ASHRAE Journal - January 2013 - Cover3
ASHRAE Journal - January 2013 - Cover4
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