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Part 4: Direct-Digital Controls Improve Schools' Energy Efficiency
By Chris Matt, Managing Editor - Print & E-Media
December 2010 -
Often due to a lack of space for geothermal wells, not every site is appropriate for a geothermal installation. One such case is Moulton Elementary School, a 122,000-square-foot, K-8 facility. The district had built an addition to the school with a newer HVAC system but left part of an older system functioning in the building.
"Moulton was not a high achiever (in terms of energy efficiency)," Silver says. "One of the things we knew is we had steam traps in there. You lose about 30 percent of your energy when you have faulty steam traps. We went through there and tested and identified all the bad steam traps in that building and repaired or replaced all the (bad) steam traps. This past year, we also replaced a 25-year-old boiler with a much more high-efficiency unit."
Another key component to the district's HVAC upgrades is building controls, particularly replacing pneumatic controls with direct-digital-control (DDC) technology. The district recently completed controls retrofits at two elementary schools and one high school, which total 273,000 square feet.
"They tie into our building-automation system," Silver says of the controls. "That allows us to take control of a lot of that equipment that in the past was controlled at the building level. So we're able to have a better control over that with the DDC. Part of having the building-automation system is being able to schedule equipment to run when we need it and cycle it off when we don't need it. We go to a setback of 2-3 degrees at night and over weekends to save energy. And we shut down some ventilation equipment during those times when the classrooms are unoccupied."
Project Profile: Des Moines Public Schools
Part 1: School District Strives for Energy Star Ratings
Part 2: Energy-Efficiency Projects Save School District Money, Improve IEQ
Part 3: HVAC Upgrades: District Focuses on Motors, Drives, Geothermal
Part 5: Project Management: Technicians Get Involved in Design