Primary/Secondary pumping

For large chillers or where more than two chillers are needed, primary/secondary (decoupled) piping systems are often used. To reduce installation and operating costs, it is best to vary the system flow so that the chilled water delta T remains constant during partial load conditions and chilled water flow varies in proportion with the load. By varying the flow, smaller pumps and piping can be used. Also, primary/secondary systems provide constant flow through the chillers to maintain chiller stability.