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					Lawrence Street Center
     Case Study

    Craig Griffiths
     Merrill Lynch
Lawrence Street Center


         • Steel & concrete structure
         • Concrete & glass wall
           construction
         • 14 floors, 140,000 sq.feet
         • Commercial offices & radio
           stations
         • 6 am to 6 pm operation
      Lawrence Street Center
            Project Scenario

• Inefficient cooling system
  – oversized chiller running at low part load
    efficiencies
• 15 year old electric chiller, CFC
  refrigerant R-11
• Public Service Company utility rebate
  program currenlty in effect
        Lawrence Street Center
              Internal Loads


• Lighting with standard fluorescent
  fixtures
• Office equipment - PC’s, copiers, fax
  machines
• Telecommunications equipment for
  four radio stations
      Lawrence Street Center
          Project Challenges


• Space constraints on chiller make
  replacement very difficult
• Quick turnaround time necessary
  – only 3 weeks for retrofit work before
    spring startup
Lawrence Street Center
    Original Chiller


               • 400 ton Carrier electric
                 chiller
               • R-11 refrigerant
               • 0.72 kW/ton full-load
                 efficiency
               • Only operating at 60%
                 capacity
               • In third floor
                 mechanical room
           Lawrence Street Center
           Chiller Driveline Retrofit


• Replaces the driveline, including starter,
  motor, compressor, purge unit and controls
• New parts compatible with new refrigerant
  – HCFC-123 used in Lawrence Street Center
• Kept old heat exchanger
  – checked the shells & tubes condition with eddy
    current testing of the condenser and evaporator
• Retrofit work by York International
         Lawrence Street Center
        Other Chiller Enhancements


• External oil pump installed
  – allows chiller operation at a lower condenser
    water temperature
  – more energy savings when ambient conditions
    permit
• New chiller control panel
• Refrigerant monitoring system and high-
  efficiency purge unit
               Lawrence Street Center
                  Retrofitted Chiller


• Capacity reduced from 400 tons to 290 tons
• Full load electricity use down to 0.59kW/ton
  from 0.72 kW/ton
    Retrofit       Rebate     Annual     Payback
     Cost                     Energy      Period
                              Savings     (years)
    $ 94,000       $ 32,000   $ 12,500      4.96


• Payback period of 7.5 years without rebate
           Lawrence Street Center
                Project Timeline




• Chiller retrofit work generally takes 1-2 months,
  this was a rush job, done in 3 weeks
           Lawrence Street Center
             Energy Savings Results


• Occupancy increased significantly during and
  just after the retrofit occurred
  – from ~ 75% occupancy to ~ 95%
• Utility bills stayed about the same as during the
  last cooling season
• Chiller downsizing and efficiency gains offset
  the occupancy increase
         Lawrence Street Center
               Project Results


• Significant energy savings from more
  efficient, correctly sized chiller
• Switch to HCFC refrigerant
  – no longer have to deal with escalating R-11
    prices
• Fairly short payback period, thanks to
  utility rebate
          Lawrence Street Center
          Extension of Project Results

• Most chillers are incorrectly sized
  – measure energy use carefully to see how much
    downsizing and/or staging of chillers can save
• Load reductions and system improvements
  could have been done with chiller work
  –   save even more energy and $$$
  –   potential to downsize chiller even further
  –   help finance chiller and reduce payback period
  –   correct any building problems

				
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