Trane SYS-APM001-EN manual System Design Options

System Design Options

Misconception 2—Low flow only works for specific manufacturers’ chillers.

Demirchian and Maragareci12, Eley13, and Schwedler and Nordeen11 independently showed that system energy consumption can be reduced by reducing flow rates. It is interesting to note that in the systems studied, three different chiller manufacturer’s chillers were examined, yet the energy savings only varied from 2.0 to 6.5 percent. In all cases, regardless of which manufacturer’s chillers were used, the system energy consumption was reduced. In addition, Demirchian and Maragareci12, and Schwedler and Nordeen11 also noted reduced first costs.

Misconception 3—Low flow can only be applied to new chilled-water systems.

As previously discussed in “Coil response to decreased entering water temperature” on page 33 and “Cooling-tower options with low flow” on page 34, there are distinct opportunities to use existing infrastructure (pumps, pipes, coils, and cooling towers) to either expand available cooling capacity and/or reduce system energy costs by using lower flow rates. Upon examination, it is clear that low-flow systems allow savings even on short piping runs, work with all manufacturers’ chillers, and can be used in retrofit applications. As a designer, remember to review the benefits to the building owner. Often, reducing flow rates can provide significant value.

Consulting engineers, utilities, and ASHRAE have all concluded that reducing chilled- and condenser-water flow rates (conversely, increasing the ΔTs) reduces both installed and operating costs. It is important to reduce chilled- and condenser-water system flow rates to provide optimal designs to building owners and operators.

SYS-APM001-EN Chiller System Design and Control 41