Commercial Condensing Boiler Optimization Final Report

Abstract

This report summarizes the findings of a field research study that assessed the impact of real operating conditions on commercial condensing boiler energy efficiency. It also identifies methods for utility programs to improve performance. The study investigated impacts of actual boiler temperature, load fluctuations, tuning, and staging control through long-term field monitoring in 12 buildings in the upper Midwest.

While there were significant variations between building types and individual sites, the condensing boilers achieved a little over half of the savings that might be expected from the rated efficiency. The average achieved efficiency of the condensing boilers was 88.6%, which is about 5 percentage points below the average rated efficiency. The study also estimated savings for a number of measures that can cost-effectively improve efficiency both at the time of installation and afterwards. These included low cost control and tuning changes that could have increased savings by as much as 3% and more extensive piping changes that could have achieved another 2% savings in half of the buildings. Finally, local boiler industry professionals were surveyed to gauge the perceived value of possible utility program features that could increase achieved efficiency of condensing boilers.

The survey results provided further evidence of the prevalence of opportunities to improve controls, and highlighted the perceived value of commissioning and operator training.

This project supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program.