Low-NOx Boilers Deliver Reliability, Redundancy Required by University

When Steven Bowman arrived at Tarleton State University in Stephenville, Texas, as director of energy and utilities operations, one of the biggest challenges awaiting him was expansion of the growing university's HVAC system. It quickly became an urgent project, as the central boiler plant had to be shut down or repaired six times during Bowman's first year.

After measuring and evaluating the overall system's operating parameters, Bowman identified the root of the problem: the 10-year-old Scotch-marine-style boiler plant.

“We had a condensing system without a condensing boiler,” Bowman said. “On average, the 350-hp winter boiler provided 150°F supply water, which typically returned at just 120°F. Because the equipment was not built with stainless-steel materials, it was unable to handle the condensing operation and quickly became a maintenance nightmare. Plus, the 100-hp summer boiler offered no real redundancy.”

With no true backup, repairs had to be made immediately, often during off-hours, which meant higher labor costs.

After a thorough evaluation, Bowman selected four AERCO Benchmark 3.0 Low NOx (BMK3.0LN) boilers, each of which delivers approximately 90 hp. The condensing boilers feature 15-to-1 turndown, a marked improvement over the 3-to-1 turndown of the previous equipment. According to Bowman, effective condensing and robust modulation have improved the system's efficiency from 48 percent to 91 percent. Additionally, natural-gas usage has been reduced 64.1 percent.

In addition to improved efficiency, the four boilers give the new system redundancy.

The Benchmark series offered flexible venting options and eliminated the need for primary/secondary piping, which simplified and expedited installation.

“We needed to move quickly because we wanted to get the new AERCO boilers installed for the 2007-2008 heating season,” Bowman explained. “As of the new year, the system was fully operational and providing heat to four buildings on campus.”

The installation of the four BMK3.0LN units was the first phase of a $15 million overhaul of the university's HVAC infrastructure. Bowman plans to replace a steam heating loop, install new chillers, and run new piping. Eight more Benchmark units are scheduled to be installed by the end of summer 2009.

The initial results have Bowman excited about the savings the university could realize when the project is completed.

“Our goal was 30-percent improvement, but our initial savings have been well above that,” Bowman said. “Once the project is complete, and we fine-tune everything, we will probably even go above our initial numbers.”

Information and photographs courtesy of AERCO.

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