Central Utilities

CUStats

 

    • 38,000 tons of centrifugal cooling capacity 


    • 4.5 miles of chilled water distribution system piping
       

    • System volume is 1.5 million gallons +

       
    • Serving 52 buildings


    • 99 million ton-hours chilled water production in 2010

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Claude Smith Cleaning Chiller Volute



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James Bowman and Don Brown Replacing a 1750 HP Motor

The centralized cooling distribution system consists of three central plants with a total of 38,000 tons of centrifugal cooling capacity connected to 4.5 miles of chilled water distribution system piping.  The distribution system piping ranges in size from 6 inch up to 36 inch.  Total chilled water distribution system volume is 1.5 million gallons +.  The distribution system serves 52 buildings totaling approximately 8 million square feet with a peak cooling load of 28,000 tons.  Our annual chilled water production in 2006 was over 81 million ton-hours.  By 2010 our chilled water production had increased to over 99 million ton-hours, an 18% increase.  Our minimum cooling load is around 5,500 tons during the winter months.  The three central plants are manned and are in operation 24 hours a day, 7 days a week, 365 day a year.  We have 13 Central Plant Operators who work around the clock to keep the plants operating.    Of the 52 buildings served by the central plants, 60% of those are Hospital operations, including patient care.  The remainder is research and comfort cooling.  Every building connected to the distribution system is equipped with a flow meter measuring the chilled water flow in the supply line to the building as well as the supply and return temperatures.  Every building is charged a price per MMBTU consumed monthly.   

The central plants capacity is made up of industrial centrifugal chillers ranging in tonnage from 2,000 tons up to 4,000 tons each.  The plants are designed for a 54 degree return and a 42 degree supply temperature, and are set up for 2 gpm per 1,000 tons.  The central plants are PLC controlled to maximize the operation and efficiency of the plants.  Two major projects were implemented to help improve our efficiency. One improvement was made several years ago to increase our delta-T and efficiency by removing all the three-way valves throughout the distribution system.  This eliminated the low-delta-T syndrome and increased our efficiency.  Another project was started several years ago which was to replace old 78 degree wet bulb design towers with high efficiency 80 degree wet bulb design towers.  This enables us to drive down our entering condenser water temperatures throughout the year below design entering condenser water temperatures, which allows us to take advantage of increased efficiencies due to tower relief.  These two improvements, along with our knowledgeable plant operators, have helped us realize an average chiller efficiency of 0.59 kw per ton in 2010.

In addition to our 24 hour a day central plant operations personnel, we also have 22 employees made up of Chiller Mechanics, Repairmen, an Electronic Tech II, and a Procurement/Expeditor who provide preventive maintenance and repairs on the 38, 000 tons of centrifugal chillers and ancillary equipment within the central plants.    We also provide emergency repairs, including chiller rebuilds, when the need arises.  These 22 employees also run and maintain 19 smaller chillers totaling 7,898 tons of centrifugal cooling in our decentralized buildings on Campus.  These buildings are not currently being served by the centralized distribution system, but are being added as additional plants and piping are installed.  Our preventive maintenance schedule runs 10 months out of the year, and includes all the general maintenance activities.

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