100 200

Kleberg Building Chilled Water Consumption

Kleberg Building Chilled Water Consumption

Figure 26.13 Pre-CC and post-CC chilled water consumption at the Kleberg Building vs. daily average outdoor temperature51.

Figure 26.13 Pre-CC and post-CC chilled water consumption at the Kleberg Building vs. daily average outdoor temperature51.

• Economizer—set to maintain mixed air at 57°F whenever outside air below 60°F

• Static pressure control—reduced from 1.5 in^O to 1.0 inH2O and implemented night-time set back to 0.5 inH2O

• Replaced or repaired a number of broken VFD boxes

• Chilled water pump VFDs were turned on.

Additional measures implemented included changes in CHW pump control—changed so one pump modulates to full speed before the second pump comes on instead of operating both pumps in parallel at all times, building static pressure was reduced from 0.05 in. w.c. to 0.02 in. w.c., and control changes were made to eliminate hunting in several valves. It was also observed that there was a vibration at a particular frequency in the pump VFDs that influenced the operators to place these VFDs in the manual mode, so it was recommended that the mountings be modified to solve this problem.

These changes further reduced chilled water and heating hot water use as shown in Figures 26.12 and 26.13 for a total annualized reduction of 63% in chilled water use and 84% in hot water use. Additional follow-up conducted from June 1998 through April 1999 focused on air balance in the 12 laboratory zones, general exhaust system rescheduling, VAV terminal box calibration, adjusting the actuators and dampers, and calibrating fume hoods and return bypass devices to remote DDC control52 (Lewis, et al. 1999). These changes reduced electricity consumption by about 7% or 30,000 kWh/mo.

In 2001 it was observed that chilled water savings for 2000 had declined to 38% and hot water savings to

62% as shown in Table 26.6. Chilled water data for 2001 and the first three months of 2002 are shown in Figure 26.14. The two lines shown are the regression fits to the chilled water data before CC implementation and after implementation of CC measures in 1996 as shown in Figure 26.13. It is evident that consumption during 2001 is generally appreciably higher than immediately following implementation of CC measures. The CC group performed field tests and analyses that soon focused on two single-duct VAV AHU systems, two chilled water pumps, and the Energy Management Control System (EMCS) control algorithms as described in Chen et al.53 Several problems were observed as noted below.

Problems Identified

• The majority of the VFDs were running at a constant speed near 100% speed.

• VFD control on two chilled water pumps was again bypassed to run at full speed.

• Two chilled water control valves were leaking badly. Combined with a failed electronic to pneumatic switch and the high water pressure noted above, this resulted in discharge air temperatures of 50°F and lower and activated preheat continuously.

• A failed pressure sensor and two failed CO2 sensors put all outside air dampers to the full open position.

• The damper actuators were leaking and unable to maintain pressure in some of the VAV boxes. This

Table 26.6. Chilled water and heating water usage and saving in the Kleberg Building for three different years normalized to 1995 weather54-

Baseline (MMBtu/y r)

Post-CC Use/Savings

2000 Use/Savings

Use (MMBtu/y r)

Savings %

Use (MMBtu/y r)

Savings (%)

0 0

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