Trane SYS-APM001-EN manual System Configurations Production, Production loop

System Configurations

Production

An individual production (chiller) pump need only pump water from the return bypass tee (point A in Figure 29), through its chiller, and into the tee at the supply-end of the bypass line (point B in Figure 29). This represents a relatively small pressure differential and a low pumping-power requirement. In addition, each individual pump operates only when its corresponding chiller runs. Production loops are independent of one another, as well as from the distribution loop. They may consist of pump–chiller pairs that act as independent chillers. Or, manifolded and stepped pumps can be teamed with automatic, two-position chiller valves to operate in the same way as pump– chiller pairs. Figure 29 shows the latter arrangement. Temperature control is also independent. The conventional chilled-water temperature controller furnished with the chiller serves this function.

Figure 29. Production loop

Automated Isolation

Valves

Chiller 3

Production

Pumps

Chiller 2

Chiller 1

Production

A Bypass Line B Distribution

Return

Supply

Chillers may be of any type, age, size, or manufacturer. System operation is simplest, however, if all of the chillers are designed to operate with the same leaving chilled-water temperature and through the same system temperature rise (temperature difference) across the chiller.

Note: If the chillers in a decoupled system make the same chilled-water temperature, then all the operating chillers are loaded to equal percentages. There may be times when preferentially loading a chiller is desired. This is discussed in “Preferential Loading” on page 73.

SYS-APM001-EN Chiller System Design and Control 47