McIntosh Middle School
TRANE GOES TO WORK TO PROVE EFFICIENCY AND IAQ CAN WORK TOGETHER
McINTOSH MIDDLE SCHOOL INCREASES CHILLER TONNAGE AND OUTSIDE AIR AND STILL SEES SAVINGS.
In some people’s minds IAQ and energy efficiency are opposing forces, but McIntosh Middle School in Sarasota, Florida gave Trane the ideal circumstance to prove that is not the case. The school, facing compliance with new ASHRAE standards, had already started the process of analyzing its current HVAC system. Their existing cooling system consisted of two 150-ton Trane reciprocating water-cooled chillers and unit ventilators in each classroom. The system had been installed in 1970 and had served well, but age—and more stringent IAQ standards—necessitated change. In order to improve IAQ the school wanted to go with a 100 percent outside air technology, but couldn’t afford the additional costs normally associated with switching to an outside air supply.
Robert Wegmann, of Facilities Resources Management Co. (FRMC) in Madison, CT proposed a system that used some of the principles of Trane’s EarthWise design, including the use of a 360-ton TRANE CenTraVac™ centrifugal chiller, the only chiller to have received the U.S. Environmental Protection Agency's Climate Protection Award. The system also used a Marley stainless steel cooling tower, four dedicated IAQ Trane air handlers for precooling 21,240 cfm of outside air, 15 Calmac ice storage tanks and a TRANE Tracer DDU building and management system to optimize system performance and efficiency savings. This solution was met initially with some resistance because the district had tried the thermal storage approach before and found it lacking. On further study, it became clear that it was not the technology that failed, but schools had failed to use the technology correctly. So, in a sense, McIntosh was a chance to prove what this system could do with the right components and the right training.
After the new equipment was in place, McIntosh’s existing fans were cleaned and serviced. The four new air coolers were set to supply pre-cooled outside air at a minimum rate of 15 cfm per occupant. The intake vents were fitted with modulating dampers, which can be adjusted for periods of light occupancy or closed completely for night and weekend shutdowns. Gravity dampers to interior halls provide passive cooling with ventilation air, and most important 1,350 ton-hours of ice storage provide full cooling capacity. This allows the system to switch off power during on-peak billing hours and provides a significant level of redundant cooling for emergencies. Finally, TRANE Tracer controls make sure the system is always operating at peak efficiency. Now McIntosh enjoys the much-improved IAQ provided by increased ventilation. And, even though they have increased chiller tonnage and outside air supply, they are still saving an impressive 19 percent a year reduction on energy costs. These types of solutions seem extraordinary to some, but at Trane it’s just business as usual.
|