In the cold climate of the upper Midwest, air-source VRF systems have difficulty meeting heating loads when the outdoor temperatures drop below -5ºF. Because of this difficulty during common cold spells, they are either oversized (adding to system cost) or supplemental heat is added (adding to operating cost). Cold temperatures can also cause frost issues around outdoor units, as well as compressor failure. A VRF system served by a water loop—in place of air—does not have these issues, making the technology more practical and effective in cold climates such as the upper Midwest. A water-source VRF system can be connected to a boiler and cooling tower or, for even higher performance, a ground heat exchanger.
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This brochure describes the USD 422 K-12 School in Greensburg, Kansas.
To maximize the respective benefits of open- and closed-loop systems, and minimize their limitations, the California Lighting Technology Center (CLTC) developed a dual-loop photosensor control system for skylight applications. The system features a control algorithm that monitors the open- and closed-loop photosensors and controls the electric light to provide the designed light level. It also automatically recalibrates nightly to adjust to long-term changes to the interior space. Results show the dual-loop technology delivers more consistent lighting and greater energy savings.
The California Energy Commission’s Public Interest Energy Research (PIER) program sponsored development of bi-level parking garage luminaires for the University of California, Davis that integrate intelligent controls with bi-level electronic drivers or ballasts to control light output based on garage occupancy. Luminaires operate at a reduced level during vacancy and switch to full light output upon occupancy. Many of the products may be combined with traditional photocontrols to maximize energy savings.