HVAC
Research | December 20, 2018
Application of air source variable refrigerant flow in cold climates
Variable refrigerant flow (VRF) systems use variable speed, split heat pumps to provide space heating and cooling to a building's conditioned areas. Air source VRF systems perform best in moderate climates, as they typically lose capacity and efficiency at low ambient temperatures—or moderately low wet bulb temperatures where defrost is required—and may be supplemented by an additional heat source. More
Research | December 19, 2018
Energy savings and lessons learned from observed, practical approaches to demand control ventilation
Demand control ventilation (DCV) systems use sensors — generally either CO2 or occupancy sensors — to estimate the actual number of people in an area and supply only as much ventilation air as is needed at a given time. DCV has the potential to save a substantial portion of building energy use in extreme climates like the northern Midwest. More
Publication | March 1, 2017
RTUs are used in more than one third of U.S. commercial buildings, the highest of any cooling equipment type. Why? They are reliable and have a low capital cost, as well as established service and distribution networks. There is anecdotal evidence, however, that these systems operate inefficiently. To validate or refute this evidence, we conducted a multi-level field study sponsored by Minnesota Department of Commerce, Division of Energy Resources. More
Publication | November 30, 2015
Variable Refrigerant Flow (VRF) systems have developed into a promising emerging technology. While popular in some places in the world, these systems are quite new to the upper Midwest. The systems are an innovative version of a simple split system air conditioner that utilizes variable speed compressors, multiple zone refrigerant distribution, heat recovery, and low energy fan coils to cool and heat commercial buildings more efficiently than standard split systems and heat pumps. More
Publication | July 1, 2015
Demand control ventilation (DCV) systems use sensors—generally either CO2 or occupancy sensors—to estimate the actual number of people in an area and supply only as much ventilation air as is needed at a given time. DCV has the potential to save a substantial portion of building energy use in extreme climates like Minnesota and other areas of the northern U.S. More
Publication | March 1, 2015
This white paper outlines the optimal control strategies for designing and operating air source VRF systems in cold climates.
Report number: 275-1 More