Rooftop units (RTUs) are commonly used in commercial applications due to their inherent convenience: RTUs package heating and cooling equipment together in a space that doesn’t take up precious real estate and is still accessible to technicians. Condensing rooftop units (C-RTUs) have recently entered the commercial RTU market, providing the benefits of non-condensing RTUs at much higher efficiency levels and lower operating costs. In fact, condensing furnaces can achieve over 90 percent AFUE—a big upgrade when compared to traditional gas furnaces that range between 78- and 82-percent AFUE.
How It Works
C-RTUs work similarly to traditional gas RTUs with one crucial difference: the condensing systems use a secondary heat exchanger to extract heat from the flue gases—heat that would have otherwise been lost.
Note: This drawing is for illustration purposes only and does not represent the sizing or depth of the system or frame for all manufacturers' products. Check with manufacturer for exact measurements and specifications.
Performance and Application
To better understand system challenges and to evaluate field performance, user acceptance, reliability, and energy savings potential in the Northwest, BetterBricks partnered with local utilities and businesses to install and monitor four C-RTUs during the 2018/2019 heating season.
The study found that C-RTUs have proven potential to achieve greater gas savings than standard efficiency units, including 1) Improved performance with 10-15% higher heating efficiency, and 2) Up to 11.5% reduction in gas energy usage.
C-RTUs are optimal for commercial buildings with high outside air usage, such as facilities that use dedicated outside air systems (DOAS) or make-up air units (MUA). They’re also especially effective in buildings with extended runtime cycles and relatively few service zones—e.g., retail big box and mall outlets, schools, sports arenas, theaters, medical/healthcare facilities and daycares.
Installation Resources
- Ideal Building Candidates
- Installation Tips: A two-page installation reference tool when installing a C-RTU.
- Installation and Best Practices Guide: A comprehensive guide of best practices for optimal installation.
- Field Study Comprehensive Report: Detailed findings from the field study completed in 2018/2019.