South Portland High School in South Portland, Maine, recently underwent a major renovation. More than 100,000 sq ft was added to the school, bringing the total to 300,000 sq ft. In addition to modernizing and expanding the school, which was constructed in 1952, the renovation provided the opportunity to implement a number of energy-saving initiatives.
The retrofit of the entire building envelope enabled Auburn, Maine, architecture and engineering firm Harriman to recommend the school switch from a traditional steam heating system to a highly efficient hydronic one.
When it came time to select a hydronic boiler system, Harriman consulted with Chuck Cyr, sales engineer for The Blake Group in Portland, Maine. Cyr recommended that only boilers capable of dual return be evaluated.
Most hydronic systems blend returns from different loops, which compromises the performance of condensing-boiler systems. Hydronic boilers with dual return have been shown to be 6-plus-percent more efficient than hydronic boilers without it.
In the case of South Portland High School, boilers with dual return were designed to meet both central-heating and domestic-hot-water needs.
When the engineering team set out to compare hydronic systems capable of dual return, it analyzed terminal-unit water-temperature parameters. The team wanted to select a unit capable of achieving the lowest water temperature to ensure the system operated in condensing mode as much as possible. Additionally, it wanted the boiler to be zero-flow tolerant, capable of handling low- and zero-flow situations.
Cleaver-Brooks ClearFire units best met the engineering team’s requirements. The building team was familiar with the manufacturer because the school had been operating Cleaver-Brooks 250-hp steam boilers for years.
Cyr worked with the engineers to develop the piping diagram for the dual-return feature of the hydronic boilers. During the summer of 2012, four ClearFire-C fully condensing boilers were installed at South Portland High School.
“Dual return on this job allows us to do domestic hot water with the boilers,” Cyr explained. “That fundamental capability coupled with the primary/secondary piping is what elevates this job to world-class status. Of the four boilers, two are capable of doing domestic hot water simultaneously.”
Russ Brigham, director of building and grounds for South Portland School Department, said the school will realize significant fuel savings. During the one-and-a-half years of construction, with doors and windows open and, in many cases, covered with plastic, the school ran heat to help the sheetrock, paint, and other construction materials dry. During construction, the school’s fuel bill with the new hydronic-boiler system was about what it was with the steam system prior to construction.
“We increased the size of the school by 100,000 ft,” Brigham said. “If the average energy requirements that I have for the past few years remain the same, I’m going to have a wonderful savings.”
Additionally, Brigham said, the low emissions of the new boilers will help the school in its pursuit of LEED certification.
Sean Lobdell is product manager for the ClearFire line of hydronic boilers for Cleaver-Brooks.