The rooftop unit (RTU) decision tree can be used for preliminary screening for replacement of RTU units with more efficient units. This decision tree organizes RTUs into bins for “retrofit,” “replacement,” “no action,” or “needs further analysis.”
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Older, inefficient commercial rooftop unit (RTU) air conditioning systems are common and can waste from $1,000 to $3,700 per unit annually, depending on the building size and type. By replacing or retrofitting them, you can save money, improve your energy efficiency, make your building more comfortable, and help the environment. The Advanced RTU Campaign (ARC) encourages commercial building owners and operators to replace their old RTUs with more efficient units or to retrofit their RTUs with advanced controls in order to take advantage of these benefits. This website shows updates to the campaign including resources and progress towards the campaign's goal.
Case study describing how adidas implemented a best practice of a planned replacement program for its rooftop units (RTUs), which resulted in significant cost and energy savings. The case study outlines the planning process, implementation, results, and the future plans of their RTU replacement program.
This checklist will assist facility managers and building owners evaluate the capabilities of HVAC companies and the proposals they submit for installation of new HVAC equipment. The questions on the checklist will help owners and managers understand the requirements contained within the ACCA HVAC quality installation Standard 5.
This case study details the very successful Walgreens proactive RTU replacement program that has resulted in 50% efficiency improvements. The streamlined process allows Walgreens to reduce installed cooling capacity, increase RTU efficiency, provide improved service, and reduce overall costs compared to emergency replacements.
In 2011, the U.S. Department of Energy’s Building Technology Office (DOE’s BTO), with help from the Better Buildings Alliance (BBA) members, developed a specification (RTU Challenge) for high performance rooftop air-conditioning units with capacity ranges between 10 and 20 tons (DOE 2013). In April 2013, Carrier’s 10-ton WeatherExpert unit model was recognized by DOE to have met the RTU Challenge specifications. Carrier also committed to have its entire line of WeatherExpert models for commercial buildings compliant with integrated energy efficiency ratio (IEER) meeting the RTU Challenge requirement. This report documents the development of part-load performance curves and their use with the EnergyPlus simulation tool to estimate the potential savings from the use of WeatherExpert units compared to other standard options.
A detailed EnergyPlus model was developed for a prototypical big-box retail store. The model used the performance curves from the new model along with detailed energy management control code to estimate the energy consumption of the prototypical big-box retail store in three locations. The energy consumption by the big-box store was then compared to a store that used three different reference units. The first reference unit (Reference 1) represents existing rooftop units (RTUs) in the field, so it can be considered the baseline to estimate potential energy savings from other RTU replacement options. The second reference unit (Reference 2) represents RTUs in the market that just meet the current (2015) Federal regulations for commercial equipment standards, so it can be used as the baseline to estimate the potential for energy savings from WeatherExpert units in comparison with new RTUs that meet the minimum efficiency requirements. The third reference unit (Reference 3) represents units that meet ASHRAE 90.1-2010 requirements. For RTUs with cooling capacity greater than 11,000 Btu/h, ASHRAE 90.1-2010 (ASHRAE 2010) requires two-speed fan control or variable-speed fan control.
The following conclusion can be drawn about the comparison of energy cost for WeatherExpert unit compared to the three reference units:
• Using Reference 1 as the baseline, WeatherExpert units result in about 45% lower heating, ventilation and air conditioning (HVAC) energy cost in Houston, 55% lower cost in Los Angeles, and 35% lower cost in Chicago. The percentage savings of electricity cost is more than 50% for all three locations.
• Using Reference 2 as the baseline, WeatherExpert units result in about 39% lower HVAC energy cost in Houston, 52% lower cost in Los Angeles, and 32% lower cost in Chicago. The percentage savings of electricity cost is 44%, 55%, and 57%, respectively for the three locations.
• Using Reference 3 as the baseline, WeatherExpert units result in about 25% lower HVAC energy cost in Houston, 35% lower cost in Los Angeles, and 18% lower cost in Chicago. The percentage savings of electricity cost is 29%, 38%, and 37%, respectively.
Based on the simulation results, the WeatherExpert RTU Challenge unit, if widely adopted, could lead to significant energy, cost and emission reductions. Because the cost of these units was not available and because the costs would be specific to a given installation, no attempt was made to estimate the potential payback periods associated with any of the three reference scenarios. However, if the incremental cost relative to any of the three reference cases is known, one can easily estimate a simple payback period.
Case study on how Fontana Unified School District in southern California used grant money to install 201 high-efficiency Carrier rooftop units (RTUs) in 30 buildings across four schools, resulting in $214,000 saved per year.
Case study on how Arby's Restaurant Group's innovative approach to rooftop unit (RTU) management garnered them $287,000 and 2.9 million kWh in annual savings.