Library Adds Chillers To Boilers
This library’s services range from online learning to special programs for children, students, adults, seniors, and those interested in special areas such as genealogy, health, and computer-assisted learning. Programs by noted authors and community leaders are held regularly.
To keep up with this growth explosion, the city recently funded a major addition to the Main Library building and renovation of the original three-story building. An advanced building comfort system featuring rooftop air handlers and a high-efficiency, water-cooled screw chiller makes the building adaptable to widely changing uses.
The original library building was constructed in 1939-40 and totals 186,000 square feet. The building has a smooth limestone exterior with a classic art deco facade and window ornamentation. Heating is supplied by natural gas-fired steam boilers, which supply low-pressure steam and hot water.
In 1986, the original building was equipped with two Trane 120-ton chillers with hermetic reciprocating compressors. The units supply 45 degree F chilled water to air handlers throughout the building.
In the mid-1990s, it became apparent that the Main Library building was no longer large enough to meet the needs of the community. The decision was made to expand the building with an 85,000-square-foot addition. Toledo architectural firm Munger, Munger & Associates was named to design the addition.
New Design Utilizes The BoilersThe three-story addition is different in appearance from the original building. The new building stands on piers to create a covered parking lot area beneath the building. The exterior features long, curving walls, with much of the space dedicated to windows. A fully glazed transition section connects the two buildings.
The addition’s interior benefits from the glazing because of its open, garden-like atmosphere and flexible public space. The garden atmosphere carries over to the rooftop of the addition, which has grassy areas, planted berms, sidewalks, tables, and chairs.
The addition’s comfort system was able to utilize the existing boilers for heating, but required additional chiller capacity for cooling. The library administration chose a Model RTHC water-cooled screw chiller, which was installed in the basement. The chiller uses R-134a and features a low acoustic signature — critical for any library.
A cooling tower was added to the existing tower on the roof of the historic building. The new tower is a Baltimore Aircoil Company (BAC) Series 3000 single-cell tower with a crossflow cooling design and vertical air discharge. Design temperatures for the system are 95 degrees/85 degrees at 73 degrees wet bulb. The towers receive makeup water from the Toledo municipal water system.
The mechanical engineering work for the project was done by Korda/Nemeth Engineering, Inc., Columbus, Ohio. The general contractor was Mosser Construction, Fremont, Ohio. The mechanical contractor was Hank’s Plumbing & Heating, Toledo.
Space ConservationIn order to maximize the amount of building space available for library functions, the decision was made to install the air handlers (two Trane Aire Systems™ units) on the rooftop of the new section. One of the air handlers is sized for 30,000 cfm and the other for 26,000 cfm, both at 5 inches wg static pressure.
The air handlers have two stages of filtration, hot water heating coils, chilled-water cooling coils, and Dri-Steem gas-fired steam humidifiers. The units are equipped with supply and return fans, each with variable-frequency drives (VFDs). Both units are equipped with Sonatrol silencers for air distribution and sound control.
Air distributed from the handlers is modulated by the VFDs to maintain a duct static pressure of 1.5 inches wg at a point about two-thirds of the way down each main supply duct. Air temperatures between 55 degrees and 65 degrees are delivered to the high-pressure distribution ducts. These supply 70 VAV terminal boxes equipped with independent zone-control sensors.
Humidity ManagementChilled water is typically supplied to the air handlers from April through November, when the outside temperature is higher than 55 degrees. When outside air temperatures drop below 45 degrees, the system begins to control return air relative humidity at 30 percent. Hot water perimeter heat is also supplied at most exterior window locations, to help maintain even room temperatures.
The new air handlers are located within an enclosure on the garden-like roof of the new addition. This is designed to further minimize the acoustic impact of the air handlers, and to fit in with the building’s architectural motif.
According to Jeff Godzak, assistant superintendent of Facilities and Operations, the system’s startup went relatively smoothly. Although the air balance contractor was unable to obtain the required duct static pressure to adequately supply the north half of the building, this was solved by installing a differently sized sheave on the fan drive.
In addition, “We needed to make some adjustments to the VFDs on the air handlers, but after changing the settings on ramp-up and ramp-down times, the problems seem to be solved,” said Godzak.
Publication date: 09/15/2003