The Hill School Mechanical System Upgrade

Engineering firm: Gannett Fleming
2013 MEP Giants rank: 61
Project: The Hill School Mechanical System Upgrade
Address: Pottstown, Pa., United States
Building type: School (K-12)
Project type: System overhaul (mechanical system upgrade, fire protection system overhaul, etc.)
Engineering services: Electrical/Power, HVAC
Project timeline: March 2011 to September 2012
Engineering services budget: $520,000
MEP budget: $520,000

Challenges

In 2010, The Hill School sought a solution for its heating and cooling needs. The school, founded in 1851, had seen student enrollment grow from 25 to more than 500, and with the growth came a need to meet current and future heating and cooling demands.

In the mid-1950s, The Hill School installed an outdoor ice skating rink. The refrigeration used to make rink ice was ammonia, an eco-friendly refrigerant. As the demand for comfort cooling on campus increased, the school leadership recognized that they had a cooling source right at their fingertips that was not being used during the summer—the ice skating rink refrigeration plant. In 1990, an ice tank was installed at the ice rink cooling plant to produce ice at night. Making ice at night when the demand for electricity is lower reduced Hill’s electric rates and boosted chiller efficiencies. During the day, the ice was melted to produce chilled water that was circulated through newly installed piping located in the existing utility tunnels to air conditioning equipment in the various buildings on campus.

When the time came to update the 57-year-old chillers and ice tank, school leadership was challenged to find an approach that would enable the school to continue its energy-efficient systems and keep within budgetary constraints. Heating also was an issue. The primary source of heating for the campus was high-pressure steam generated in gas-fired boilers. Steam piping was routed through underground tunnels into each building, where its heating value was transferred to a hot water heating distribution system, or high pressure was reduced to low pressure and distributed to steam heating devices within each building. The steam piping system serving the campus was installed at various times dating from the 1930s to the 1980s, meaning much of the infrastructure was operating beyond its useful life expectancy.

Solutions

Gannett Fleming mechanical engineers solved the school’s cooling problems by installing a new chilled water/ice system refrigerated by a new electric-driven air cooled chiller and a natural gas engine-driven chiller. The gas-driven chiller takes advantage of the natural gas supply already available on campus and can be run as needed during peak cooling periods without increasing electrical cost. This approach of using what the school already had for another purpose demonstrated the sustainable design principle of using "What is in your hand?" The use of a gas-driven chiller also minimizes additional electrical load, thereby eliminating the need to upgrade the utility service capacity on campus. The elimination of electrical load because of the replacement of the cooling plant with higher efficiency equipment also resulted in a one-time rebate from the electric company totaling more than $39,000. Gannett Fleming performed an initial assessment of the steam distribution system, which indicated that much of the piping was deteriorated and in need of replacement. During the spring of 2012, the project team field surveyed and documented the entire system. The team then installed the replacement system, which is expected to provide approximately 80 years of service for the school.

The system upgrades grew out of a mechanical engineering study Gannett Fleming performed in 2010. For the study, Gannett Fleming assessed campus systems, recommended engineering solutions, and provided probable construction cost opinions and lifecycle cost estimates. Thanks to the report, the school now has a comprehensive list of all campus assets, enabling it to better manage and inventory equipment. Also, Hill leadership used the report to develop a capital budget, prioritizing infrastructure improvements and ensuring a solid infrastructure for students now and in the future.

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