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About the Project Founded as Omaha University in 1908, the current day University of Nebraska at Omaha is now the third-largest institution for higher education in Nebraska. It occupies over 158 acres of land and serves over 15,000 students and faculty. As a part of its expansion, they are adding a new LEED Silver Certified College of Business Administration named Mammel Hall. With a goal of providing occupant comfort year-round, the owner wanted to insure that the indoor climate would be controlled through potentially humid summers as well as severe winter conditions. Challenges & Considerations The Engineer’s original specification called for the addition of a boiler and significant hot water piping. This option would require a boiler to be on standby for the inevitable reheat request in order to maintain humidity control. When asked to consider electric heat as an alternative, recommended by the local Krueger Representative, Air-Side Components, the Engineer originally rejected it, stating that three-state heating was too imprecise and SCR electric heat was too expensive (often adding as much as $400/ zone between heater and controls). Product Solution It was not until subsequent discussions with both the Local Representative and Dan Int-Hout, Krueger’s Chief Engineer, that the Engineer switched the specification to electric heat. It actually offered a lower first-cost than the first option because the once needed hot water piping could be eliminated. However, we still had to address an issue with uniformly cooling all spaces. Fortunately, Krueger already had an electric heat solution that would fit that need as well as provide an opportunity to earn LEED points towards their Silver certification. Krueger’s patented LineaHeat™ option features a single-stage, time-proportional solid state relay to provide only the required amount of heat to the space. The LineaHeat controller optimizes both flow and reheat at a much lower first-cost than SCR electric heat and it has more flexiblity when it comes to controlling it. LineaHeat can accept up to seven different types of input signals, including ON/OFF, 0-10 VDC, and 3-point floating. All seven options are designed to work with standard DDC controllers currently offered on the market today, which can create an opportunity for significant first-cost savings. Additionally, there is an option to allow for precise control of discharge temperatures to maintain space temperatures. This too can be beneficial when there is a need to cost-effectively control humidity. The End Result Krueger was pleased to have provided 150 LMHS units with LineaHeat for this application and the opportunity to help achieve LEED Silver Certification on this building. The Engineer also stated that the installation has gone smoothly and that they are on target to open in August of 2010. LineaHeat allows a simple startup with little field adjustment required. The optimization of energy use that LineaHeat provides has assisted the customer in obtaining his LEED Silver rating.
Objectives To replace cooling towers located on the 52nd level of a commercial high-rise building in downtown Los Angeles. Solutions This client chose Mesa because of the company’s extensive experience in performing complex air conditioning system retrofits on a turnkey basis. From the start, Mesa faced two challenges. First, the building’s cooling had to be maintained while the cooling towers were being replaced. And second, the units were located at the top of one of the city’s tallest buildings, necessitating the use of a helicopter to lift the new units above Los Angeles’ busy streets. To address the first challenge, Mesa demolished and removed half of the existing cells, leaving the remaining cells to continue cooling the building. After mounting seismic isolation bases and springs, Mesa installed two induced-draft counterflow cooling towers. The units were ordered in multiple sections weighing less than 3,500 pounds, so they could be lifted by helicopter. Mesa made all arrangements for the helicopter operation, including obtaining street closure permits, security personnel, and contracting for trucking support services. To minimize disruption to building operations and ensure maximum safety, the company dismantled the old equipment and removed it utilizing the buildings freight elevators after hours. Mesa orchestrated the two helicopter lifts on Saturdays when building occupancy and street traffic were reduced. Each tower included three cells, each fan driven by a 40-horsepower, 460-volt variable frequency drive. Mesa provided temperature controls through an interface to the building’s DDC system, enabling monitoring of the system operation and energy consumption and operating cost reductions. Mesa installed new fan disconnect switches, water piping, two tower cleaning systems, walkway gratings, and stainless steel exhaust ducting from each cell up through the roof. After the tower installation, Mesa performed start-up and commissioning services for the first two towers and completed the same work for the second half of the cooling towers before turning the completed project over to the owner. Background City National Plaza encompasses an entire city block in the financial area of Los Angeles’ central business district. Completed in 1972, it consists of two 51-story office towers, one plaza level building, and four subterranean levels, comprising in total more than 2.6 million square feet of rentable space.
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