Market and Performance Characterization of Commercial Rooftop Units
Scott Schuetter, Mark Hancock, P.E., Alex Haynor — Jan 2015
The project team completed analyzing data from 52 RTUS at 9 sites and developed consumption profiles for each RTU and each site, and then conducted a sizing evaluation of RTUs at each site to determine their ability to meet the required load for both heating and cooling. Project lead Seventhwave will release the final report and hold a webinar to discuss results in spring 2017. Full project update
Why this research is needed
Packaged rooftop units (RTUs) serve the heating, ventilation, and air conditioning needs of a large proportion of commercial building space in the US. RTUs have several advantages over other systems in that they typically have integration of heating and cooling in one unit, low initial costs, are extremely reliable, offered in a large ranges of sizes and have an extensive network of trained installers and services technicians. However, anecdotal evidence indicates that RTUs tend to operate sub-optimally and inefficiently, suggesting considerable room for improvement. Furthermore, the majority of recommendations for RTU programs have originated in cooling dominated climates, where the standard operations and program economics are very different than those found in Minnesota.
Project process and expected outcomes
This research will build off results of CEE’s 18-month field study of RTU controller optimization.The project team will first characterize the installed RTUs in Minnesota, including which commercial buildings they serve, and the market for new and replacement RTUs. Mapping tools will be used to identify RTUs in representative geographic locations, and phone surveys with building managers will be used to gain additional information about system characteristics of individual buildings and maintenance practices for their systems.
The monitoring phase of the project will measure the energy consumption of up to 80 individual RTU units across eight to twelve sites. Energy and gas consumption will be measured over a nine to twelve month period to identify factors that lead to high and low performance. Particular attention will be paid to aspects of performance that are most important in Minnesota’s heating-dominated climate.
Project outcomes will include actionable recommendations for the development of utility programs and state energy policy for RTU energy consumption in new and existing buildings. Reports and presentations will address common elements of utility programs, including the relative benefits of proper sizing, quality installation and maintenance programs, recommissioning, controls upgrades, and partial or complete equipment change-outs before failure.
*This project is supported by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program, which is funded by Minnesota ratepayers.