Efficiency program administrators need the expertise of manufacturers, design engineers, and other professionals to ensure efficient energy use.

What Problem Was CEE Solving?

Gas boilers are often oversized for the space to be heated. Source: CEE staff photoThe CEE Commercial Gas Boiler Systems Initiative establishes a specification that defines high efficiency gas boiler and system performance with the goal of benefiting both building owners and the public. But installing efficient equipment is not all that can be done to save energy. Members reported anecdotally that boilers were routinely oversized in many customer installations. Oversized boilers lead not just to higher costs up front, but also to wasted energy over their lifespans.

By bringing the boiler size in line with the building heating requirements and the capacity of the distribution system, there’s potential to save even more energy. Modulating burners are important, but not a panacea. One question must be answered: what is the right size?

Focusing the Conversation

Over a six-month period, CEE approached commercial boiler manufacturers and other technical experts to ask for their perspective on how to correctly size commercial boiler systems. The response was impressive. Manufacturers and design engineers from across the industry agreed that oversizing is endemic, and "rightsizing" offers significant energy savings. Various methods designed to calculate heat loads are too often overlooked. And although the high turndown ratios offered by modern modulating boilers provide greater flexibility to system designers, rightsizing systems provides even more robust energy savings.

The greatest revelation was not just about boiler technology or sizing calculations. It was refocusing the conversation on maximizing energy efficiency and cost-effectiveness of the entire system.

Finding the Answer

Traditionally, boilers are sized for the highest load, which typically means the coldest day of the year. What if a new boiler is sized for the most common conditions of the year while a backup or legacy unit carries the extra load for extreme temperatures? The result is a smaller condensing unit that costs less and can offer the greatest efficiency level over the greatest number of operating hours. These hybrid systems, sometimes called mixed technology systems, combine condensing and noncondensing units. Many contributors emphasized the critical role of controls and sequencing to ensure load-sharing and redundancy across all types of system demand.Hybrid systems size for an average need, but have a back up boiler for use when needed. Source: iStockphoto

The conversation began when CEE went straight to the experts. Through this process, our understanding of rightsizing is changing to encompass a broader meaning that offers new approaches for energy efficiency programs to save energy, lower equipment costs, and improve the cost-effectiveness of efficiency programs across the United States and Canada.