23

23,000

1Measured with a Demand Meter 2Approximated using Figure 4

1Measured with a Demand Meter 2Approximated using Figure 4

and the other four are operated according to the plant's varying demand for cooling. The chillers are currently controlled by variable inlet vanes (VIV).

The typical load diversity and the power input required for one of the chillers under varying load were obtained from the manufacturer. In addition, the data in Table 2 give the power input of a proposed variable frequency drive (also referred to as adjustable speed drive (ASD)) for one chiller that operates about 6,000 hours per year.

A weighted average of the load and duty-cycle fractions gives a load diversity factor (ldf) of 64.2 percent. This means that, on the average, the chiller operates at 64 percent of its full load capacity. A duty-cycle fraction weighted average of the savings attainable by a VFD can be estimated, which is 26.6 percent savings per year. The energy savings due to avoided cost of

Table 2. Centrifugal chiller load and power input (Source: updated from Moses et Al., 1989)

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