High Efficiency Replacement Boilers

As we leave the heating season, many building owners begin repair and replacement projects in their boiler plants. Boilers that burn fuel to heat water have been around for thousands of years and technologies that we would recognize today date back to the early 1700’s. More recent trends in boiler construction and control focus on energy efficiency. The term “high efficiency boiler” usually refers to a boiler that utilizes a condensing type combustion process. In these boilers, enough heat energy is pulled from the flue gases that the entrained water vapor cools to a point where it begins to condense to liquid. These types of boilers are becoming commonplace in all sizes of boiler plants, but require some special considerations if they are part of a boiler replacement project.

  • System Design Temperature: Condensing boilers are more efficient at lower entering water temperatures. If you are replacing an existing boiler, the original design hot water supply temperature and design temperature differential need to be evaluated. In most cases, a condensing boiler will not be much more efficient than a standard boiler at 180 degree F supply water temperature setpoint. “Near condensing” type boilers may be more appropriate for these applications.
  • Flues & Chimneys: When water vapor condenses in the boiler flue gas path, it combines with other products of combustion and forms corrosive liquids like sulfuric acid. Condensing type boilers require special flue materials and may not be able to connect to existing boiler breeching or masonry chimneys.
  • Combustion Air: The boiler room needs to be evaluated for proper combustion air prior during any replacement boiler project. Many times, combustion air is ducted directly to the burner of a condensing type boiler instead of being open to the boiler room.
  • Boiler Plant Piping: Most manufacturers of high efficiency boilers provide recommended system piping diagrams in their product manuals. Multiple, condensing type hot water boilers are typically manifolded and utilize small primary circulators in addition to the building distribution pumps. The existing system piping and pumping configuration needs to be evaluated when replacing a traditional boiler.

Replacing your boilers with high efficiency, condensing type boilers is usually an energy savings measure that has a short payback period. However, the boiler plant and building heating systems need to be evaluated in their entirety to maximize performance and energy savings. If you need assistance in evaluating the installation of replacement boilers in your facility, please do not hesitate to contact Douglas C. Barnhart, PE at 717-845-7654 or dcb@ba-inc.com.

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