Green & Efficient
Adlai E. Stevenson High School Lincolnshire, Ill.
During the retrofit of Lincolnshire, Ill.'s Adlai E. Stevenson High School's indoor pool's HVAC support equipment, a contractor's unique solution saved $400,000 in construction costs. The innovative approach added to the suburban Chicago school district's progressive green mission and also promises a value-engineered resolution to the HVAC industry's impending mechanical room dehumidifier replacement challenges.
The 3,950-student school's huge 40,000-square-foot natatorium, one of only four 100-meter Olympic-sized pools in Illinois, was faced with replacing two aging HVAC dehumidifiers requiring tens of thousands of dollars annually in maintenance costs the past few years. Installed when the natatorium was built in 1996, the removal of the huge heat recovery dehumidifiers would require upwards of $400,000 in construction costs to tear open a wall or roof for their removal, according to Mark Michelini, CPA, assistant superintendent for business at School District 125.
Instead, the school district's longtime building automation and energy services contractor Siemens Industry Inc. (SII), Mount Prospect, Ill., and Michelini conceived the idea of leaving the units in place, gutting them and commissioning dehumidifier manufacturer, Seresco USA, Decatur, Ga., to factory-build entirely new 64 and 40-ton dehumidifier components, coils, piping inlet/outlet receptacles and control packages that would fit inside the original manufacturer's steel shell configurations.
The revolutionary technique was also approved by the on-site building services contractor, Sodexo, Gaithersburg, Md., Bruce Svec, sales engineer at manufacturer's representative, Imbert Corp., Niles, Ill.; and architect consultant firm, Cannon Design, Chicago. The school district signed a performance contract with SII to guarantee solving the dehumidifier replacement challenge at a specified payback and cost.
Most of the challenge rested on Seresco USA, however, which sent Vice President of Production Jonathan Theriault to ensure the critical measuring accuracy of the shells, components, various piping connections, positions of inlets/outlets and the 25,000 and 15,000-cfm blowers, the latter of which were retained to value-engineer project costs. Matching the evaporator coils was the most difficult challenge, according to Theriault.
Factory engineers then designed the entire configuration and provided the installing contractor, Team Mechanical—EMCOR Services, Buffalo Grove, Ill., with 3-D, computer-modeled blueprints to simplify on-site assembly and installation. The new partially-assembled internal component packages arrived as a compressor/refrigeration circuit skid, separate fully-dipped enamel corrosion-proof evaporator, reheat and hot water coils, Command Center/electrical control panels and dry coolers to minimize onsite assembly. "All dehumidifier manufacturers have a similar physical airflow sequence consisting of an evaporator coil, reheat coils, compressor module/refrigeration circuit and fans, but fitting equipment into another manufacturer's configuration and making it easy for the contractor to install was a custom-engineering feat," said Svec, who helped coordinate the project between SII and Seresco.
Instead of a conventional 100-percent refrigerant dehumidifier, SII chose two NP-Series Protocol models, which together substitute nearly 1,200 pounds of the original systems' refrigerant with environmentally-friendly glycol that's PVC piped to rooftop dry coolers 60 feet away for heat rejection. The units do use a substantially reduced charge of approximately 400 pounds of refrigerant R-410A, which doesn't have ozone-depleting chemicals.
The strategy of reducing potential environmentally-damaging refrigerants enhances the school district's aggressive green mission, which typically includes annual carbon footprint reductions aimed at cutting energy use by 3 percent to 5 percent annually.
The school's ongoing progressive sustainability efforts, such as high-efficiency pumps, condensing boilers, and various lighting and plumbing upgrades, for example, have led to the district's Leadership in Environmental and Energy Design (LEED) Gold certification. "Reducing refrigerant and chemical use in our building is part of our sustainability mission," said Michelini.
Besides refrigerant reduction, the new dehumidifiers also save 15 to 20 percent more energy than their predecessors via scroll compressors, direct drive fans and other comparably higher efficiency components. Besides sustaining a 50-percent relative humidity, the units use energy recovery to heat the pool water to 80°F, and maintain an 82°F space temperature.
Another key to the project's success was no downtime during the three-month retrofit. One unit operated continually while the other was retrofitted. Thus, the pool, which hosts important swimming events such as the Illinois High School Water Polo Championships and the Midwest Zone Junior Olympics, remained operational and open during its typical 16-hour days.
Michelini suspects the original dehumidifiers may have unknowingly experienced slowly-degrading inefficiencies in between annual routine service checkups. The new dehumidifiers will run efficiently because they are each outfitted with a Command Center and Ethernet connection that relays more than 100 operating parameters to Seresco's factory engineers for daily review via a proprietary web-based program. An operating inefficiency can be pinpointed and corrected the day it occurs, rather than discovered months later during a service call.
Although there were no ductwork modifications and new dehumidifiers have a similar refrigeration capacity, Michelini said there's a noticeable difference between the old and new technology in terms of air comfort, especially during meets within the 240-seat spectator section.