Decentralized boiler system schools campus in efficiency

In September 2006, Concordia University, a 187-acre campus nestled on the banks of the Huron River in Ann Arbor, Mich., began a project to reduce energy use. To accomplish this goal, the school’s engineering and management team needed to replace the existing centralized steam heating system.

The original centralized heating system consisted of three steam boilers and an underground piping distribution system, which Jerry Novak, director of buildings and grounds for Concordia, had to repair many times. A campus audit revealed that the old underground hot water distribution system was responsible for 20% to 25% of Concordia’s water usage, and was leaking heated water into the soil.

“Over the course of its lifespan, the underground piping distribution system had become rotted. We were losing a lot of water each day,” Novak said. The leaks led to high maintenance costs, elevated water and sewage bills, and a higher monthly heating bill.

Selecting the best system

Philip Leege, a semi-retired engineer, volunteered to develop an energy savings project, and to help evaluate systems and equipment recommendations. He realized that upgrading the underground piping network would be expensive, but necessary, in order to reap the full benefits of new high-efficiency equipment. To further complicate matters, a deep valley in the middle of the campus made it difficult to effectively lay replacement piping to the gymnasium. Engineers proposed the idea of having a split system, where the gymnasium would have its own boiler and the remaining campus buildings would continue to be served by the centralized boiler plant.

Leege was still undecided as to whether Concordia should design a decentralized system when he visited Aerco’s New Jersey headquarters. However, he was certain that he needed high-efficiency boilers. Based on Leege’s visit, Concordia ordered 18 Aerco Modulex units, which have been installed in eight campus buildings. Because of the different building sizes and heating demands, the project used a mix of MLX-606, MLX-757, MLX-909, and MLX-1060 boilers, which range in capacity from 600,000 to 1 million Btuh.

Boilers for every building

The move to a decentralized system rendered the existing underground piping system obsolete and significantly reduced project costs. Equally important, the decentralized system enabled the engineering team to create an operating expense management control program. As part of the program, meters were installed in all the buildings so that the heating, electrical, and water usage can be monitored individually rather than being allocated from central metering.

Before recommending the Aerco Modulex units, Leege had to ensure that the challenges associated with a decentralized system could be overcome. For one, most of the campus buildings did not have space designated for boilers when they were constructed, so installing the boilers was a crucial concern during the evaluation process. Second, multiple duplicate boilers would be chosen for each building with minimum redundancy to defend against freeze-ups if one boiler in a building was taken down for service during the peak heating season. Third, the plan would increase the number of campus heating boilers from three to 18, potentially adding to the service requirements placed on Novak’s team.

Aerco’s Modulex boilers more than met these challenges. All Aerco Modulex units have a compact footprint, with the largest for Concordia measuring a mere 49 in. wide x 27 in. deep x 42 in. high. Even when installed in pairs and/or groups of three, they were an easy fit into all the buildings. The ability to vent with PVC through either a ceiling or sidewall, and the ability to change service connection points (gas, water, air, and venting) from the left to right, also simplified installation.

Each Modulex boiler combines up to seven independent, 151,500 Btuh, pre-assembled thermal modules housed in a common enclosure. Each module has it own controller, fan, modulating gas valve, electronic ignition, modulating burner, and flow temperature sensor. If a single module requires maintenance or repair, the other modules in the unit continue operating to maintain the system load requirements. Not only is this built-in redundancy a plus, but all of the units in the line, regardless of capacity, use the same modular design, which is beneficial from Novak’s perspective.

“Even though I have 18 boilers in six different sizes, my staff only needs to learn one piece of equipment and keep just one set of spare parts on hand,” Novak said. Other Modulex features keep maintenance simple. Its snap-off enclosure panels don’t require tools for removal, and each waist-high unit provides top-lift access for fireside inspection and easy cleaning.

“My crew has gone through the first round of training with Dale Prentice Co. and already understands the capabilities,” Novak said. “The units are working perfectly so we haven’t had to do any maintenance, but I’m confident we’ll be able to handle whatever might arise.”

Cost savings

The gymnasium and student services building, each with two units, were operational for the 2006-2007 heating season. Installation in the remaining six buildings was not complete until the summer of 2007, though early returns are positive. Leege’s ongoing energy audits have demonstrated that the decentralized heating system has achieved overall efficiency of 94%, with some buildings operating at 99%. This is a far cry from the old centralized system that operated at only 70% efficiency. The improved efficiency is driven by both the system design and the high-efficiency Modulex equipment.

By moving to a decentralized system design, Concordia reduced the electrical expense for pumping throughout the underground piping system. The new condensing boilers feature very high turndown, from 13:1 to 23:1 depending upon unit, to minimize cycling and prevent wasteful temperature overshoot.

Information provided by Aerco International Inc.

AT A GLANCE

Concordia University, Ann Arbor, Mich., replaced its existing centralized steam heating system with a decentralized system that features Aerco Modulex boilers.

The condensing and fully modulating boilers, and decentralized design of the system helped the university decrease natural gas use by 39% on an annual basis.

The campuses uses a mix of MLX-606, MLX-757, MLX-909, and MLX-1060 boilers, which range in capacity from 600,000 to 1 million Btuh. Each module has it own controller, fan, modulating gas valve, electronic ignition, modulating burner, and flow temperature sensor. If a single module requires repair, the other modules in the unit continue operating to maintain system load.

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