L'Anse is a community of 4,500 located in the west-central portion of Michigan's Upper Peninsula. In 1998, voters passed a bond referendum for $9,855,000 for the purpose of building a new 52,800-sq-ft middle school, which would include classrooms, a cafeteria/auditorium, gymnasium, and library.

The referendum also included funds to replace the high school's heating plant, which featured a 4.9 MBtuh, fixed-fired gas boiler originally installed in 1977. Hitch, Inc. of Houghton, Michigan, was selected as the AE and the Barton Malow Company, with an office in Marquette, MI, the construction manager.

Sharing the Load

Rather than construct a freestanding building, a decision was made to design the new middle school with a physical link to the existing 75-year-old high school and 35-year-old elementary school buildings.

"This approach would make it possible for students in all three schools to take advantage of the modern gymnasium, cafeteria/auditorium, and library facilities of the new school," said Hitch engineer Larry Hermanson. "And not only did this benefit all students in the district, it also helped to stretch the overall construction dollars allocated to the project," he added.

Because the new middle school would be linked to both the high school and the elementary school, it became cost effective to provide the required heat from the existing elementary and high school heating systems.

Dale Prentice & Company supplied the high-efficiency equipment, which was selected to replace the 20-year-old conventional boiler in the 60,000-sq-ft high school. Three 2 MBtuh Aerco Benchmark(tm) boilers were installed to heat the high school along with the majority (42,800 sq ft) of the new middle school. The Aerco boilers are designed to use seamless modulation to eliminate cycling losses and the stainless steel, firetube design can be applied in high-delta T condensing applications to provide seasonal efficiencies as high as 96% without degrading the heat exchanger.

The 40,000-sq-ft elementary school was heated by two 80-hp Kewanee firetube boilers originally installed in 1966. Although no funds had been specifically allocated to upgrade the elementary school infrastructure, overall project savings made it possible to improve this system's efficiency as well.

As part of the project, each of the elementary school boilers was retrofitted with new Gordon-Piatt gas burners offering 88% combustion efficiency, 3.3 MBtuh maximum, and 1.1 MBtuh minimum.

Dunham-Bush air handlers were also added to the original infrastructure.

"A simple burner replacement promised minimal labor requirements and seemed the easiest and most cost-effective approach," remarked Hermanson. Equipped with new modulating burners, the boilers and air handlers were also tied into the new middle school, picking up the 10,000-sq-ft balance of its heating load.

The expansion presented an opportunity to increase the level of control John Juntunen, maintenance/transportation supervisor, had over the HVAC systems. Prior to the project, boilers in both schools were locally managed via individual aquastats on each unit.

Today, a Siemens Insight control system offers Juntunen centralized computer control over elementary school equipment and an Aerco boiler management system provides master control of the three Benchmark units in the high school. Beyond boiler operation, these advanced controls extend Juntunen's reach to ancillary equipment as well. "Today, I control all air handlers across the entire system from my computer workstation," said Juntunen.

Unexpected Savings

The expansion took place during the 1999-2000 heating season, so it wasn't until the fall of 2000 that the financial impact of the heating decisions could be felt. Laura Mathieu, the school system's business manager, was the first to notice. "I was just looking at the monthly bill and I couldn't believe it," said Mathieu. In fact, while the overall coverage area increased by 52% over the last two years, the total gas bill saw a slight decrease, with the original 1997-98 cost/sq-ft declining 38% to $0.21/sq-ft by 2001-2002. ES