Aftermarket boiler control systems offer a potential option for energy efficiency retrofits of commercial gas-fired boilers. These devices are installed on existing boilers with no interruption to boiler operation. The systems monitor boiler operation and adjust boiler cycling rates to reduce annual fuel consumption. Aftermarket boiler control systems are seeing initial market and technical success and thus, are candidates for utility-sponsored energy efficiency programs.

Through a third-party laboratory evaluation of an aftermarket boiler control system, preliminary data reported from this study quantify the fuel savings under a range of heating demand profiles. A laboratory test stand is developed to deliver a variable heating load to the test boiler in order to simulate a typical building installation. The Department of Energy (DOE) Energy Plus model, using the standard reference building model of a secondary school, is used to create a 24-hour heating demand profile for typical commercial buildings.

Boiler operation and energy consumption is monitored under both steady-state heating loads and 24-hour simulated heating demand profiles. Fuel consumption is measured with and without the aftermarket control system to determine the reduction in burner cycles, fuel savings, and system temperatures. Under most conditions, the aftermarket control system reduces boiler cycling and fuel consumption as compared to the baseline tests. The maximum fuel savings occurs during periods of peak heating demand. However, the magnitude of fuel savings varies depending on the control setpoints of the boiler, specifically the aquastat differential (or deadband). This paper summarizes preliminary data from this laboratory evaluation of an aftermarket boiler control system within a range of heating loads to aid in the identification of applications where it may provide the most fuel savings.