Like many older schools, Geyer Middle School in Fort Wayne, Indiana, was heated by two large steam boilers. In 2001, the school embarked on a project to replace these 42-year-old units with high-efficiency AERCO equipment.

“We initially installed two 2.0 million BTU/hr. Benchmark units to handle the 118,084 sq. ft. building,” said Stephen Novell, supervisor of Mechanical Maintenance at the Fort Wayne Community School System. “We kept one of the old boilers because a portion of the building remained on a steam system. In 2002, we pulled the last steam boiler and converted the remainder of the building to hot water. At this point we also installed a third Benchmark unit. It provided the capacity cushion we wanted while adding to the efficiency profile of the overall heating plant.”

Because the Benchmark is designed to condense, Novell simplified the school’s heating system. The era of mixing valves, hot water mixing loops and temperature averaging components to protect the boilers from thermal shock was over. All of this became unnecessary with the efficient Benchmark’s condensing capabilities – the process of extracting latent energy from water vapors created during the combustion process and releasing it as usable heat.

Just as important to thermal efficiency is the Benchmark’s modulating design, which precisely matches the boiler’s firing rate to actual building demand.

Rather than incur burner cycling losses and wasteful overshooting, which stems from a strictly “on/off” burner operation characterized by the old boilers, each 2.0 million BTU/hr. Benchmark can run with as little as 100,000 BTU/hr. – or 5% input. The Benchmark can gradually increase capacity as needed – in precise 1% increments – until it’s firing at 100%. In fact, the lower the firing rate, the higher the Benchmark’s efficiency.

To fully leverage this capability, the three Benchmark units function as a single system under AERCO’s Boiler Management System (BMS). The BMS regulates the units to operate in tandem, providing them with precise firing instructions that ensure maximum efficiency. It is more efficient for the three boilers to run at 30% input than for two to run at 45%, or for one boiler to run at 90% of capacity. The BMS also consistently rotates the lead boiler in the plant so that each unit receives approximately the same amount of work over the course of the season.

“We’ve achieved a massive decrease in natural gas consumption since switching to AERCO,” said Novell. “They run great, they save us money, and because we haven’t had any maintenance problems, we barely notice they’re there. That’s exactly what someone wants in a heating system.”

When comparing energy consumption of the steam plant in the winter of 2001 to the more severe winter of 2003 with the Benchmark plant fully in place, energy consumption decreased by 29.43%.