Optimizing Chilled Water Plant Performance. David Herman, PE, LEED AP Principal EnerG Associates, LLC

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1 Optimizing Chilled Water Plant Performance David Herman, PE, LEED AP Principal EnerG Associates, LLC

2 Optimizing Chilled Water Plant Learning Objectives Performance Review the design and operating characteristics of each equipment component of a chilled water plant Understand how the design characteristics and operation of each equipment component effects overall chiller plant efficiency Learn how to evaluate strategies to optimize chilled water plant performance based on existing chilled water plant design and operation Review actual operating data from central chilled water plants before and after implementation of optimization strategies 3/6/2014 2

3 Optimizing Chilled Water Plant Performance Benchmark the existing equipment Ensure proper preventive maintenance Optimize operation of existing equipment Evaluate possible capital retrofits 3/6/2014 3

4 A Typical Chiller Plant 3/6/2014 4

5 A Typical Chiller Plant What is the average total kw/ton for an existing chiller plant including chillers, cooling towers and pumps? Approx. 1.0 kw/ton What is an optimized total kw/ton for a chiller plant? Approx kw/ton (lower with capital investment) 3/6/2014 5

6 Benchmarking Pumps What is one of the most useful diagnostic tools for benchmarking pumps? The Pump Curve 3/6/2014 6

7 Benchmarking Pumps Example: TACO Model #TA1538 HP 75 GPM 1400 HD 140 IMP 12.5 RPM /6/2014 7

8 Benchmarking Pumps 3/6/2014 8

9 Benchmarking Pumps How can pump impeller size be confirmed? By deadheading the pump 3/6/2014 9

10 Benchmarking Pumps 3/6/

11 Benchmarking Pumps 3/6/

12 Benchmarking Pumps Why is it important to use the same gauge to measure suction and discharge pressures? To avoid gauge error since the differential pressure is needed 3/6/

13 Benchmarking Pumps Example: Measured Suction P: 9 psig Measured Discharge P: 58 psig Measured ΔP: 58 psig Measured ΔP: 134 head To convert psi to head, multiply by 2.31 Deadhead: 163 3/6/

14 Benchmarking Pumps 3/6/

15 Benchmarking Chillers Basic Formulas 1 ton = 12,000 Btuh GPM = Q / (500 x ΔT) Tons = GPM x ΔT / 24 3/6/

16 Benchmarking Chillers What ΔT is the basis of the rule of thumb of 2.4 GPM/ton for evaporator flow? ΔT = 10 degrees 3/6/

17 Benchmarking Chillers Tag # Manuf Model # Nom Tons #1 Trane CVHE090R #2 Trane CVHE090R #3 Trane CVHE 050 F BC 515 Evaporator GPM Ent Temp Lvg Temp Temp Diff 1, , Condenser GPM Lvg Temp Ent Temp Temp Diff 1, , , FLA kw kw/ton Refrig Charge Starts Hours R 123 1,111 34, R 123 1,131 25, R ,276 > /6/

18 Benchmarking Chillers Barrel Nom Tons Rated Flow Rated PD FT Rated Temp Diff Evap Cond 1, Meas Ent P Meas Lvg P Meas Diff P Meas PD FT Meas Flow ,543 Meas Ent T Meas Lvg T Meas Temp Diff Tons Amps kw kw/ton /6/

19 Benchmarking Chillers Measured Flow = Rated Flow * (Rated PD/Measured PD)^0.5 kw = (3)^0.5 *V * A * PF / /6/

20 Ensure Proper Maintenance Pumps Chillers Cooling Towers 3/6/

21 Optimize Pump Operation Over pumping results in: Flow problems Energy penalty 3/6/

22 Optimize Chiller Operation Lower condenser water temperature set point For every one degree drop in condenser water temperature, chiller efficiency will increase 2% Consider the trade off between lower compressor energy and increased cooling tower fan energy 3/6/

23 Optimize Chiller Operation What is the typical location of the differential pressure sensor controlling the pump variable speed drive? Somewhere along the chilled water supply and return piping What is the optimum location? 3/6/

24 Optimize Chiller Operation Relocate differential pressure sensor controlling pump variable speed drive Optimum location is across the chilled water supply and return piping at the farthest chilled water coil 3/6/

25 Evaluate Capital Retrofits Install variable speed drive on existing chiller(s) Significant energy savings in chiller energy use is possible (up to 30% in some applications) 3/6/

26 Optimizing Chilled Water Plant Performance Benchmark the existing equipment Ensure proper preventive maintenance Optimize operation of existing equipment Evaluate possible capital retrofits 3/6/

27 To download a copy of this presentation, go to 3/6/