Technical Case Study: Mitigating Low Delta-T Syndrome in High-Capacity Chilled Water Networks

Low Delta-T Syndrome is a critical operational anomaly that severely degrades central plant efficiency in primary-secondary chilled water networks. When return water temperatures drop below design specifications, chillers operate under low thermal loads while pumping energy increases exponentially. This technical case study details the field-based diagnosis, thermodynamic impact analysis, Testing, Adjusting, and Balancing (TAB) interventions, and control re-engineering applied to a 4,500-RT chilled water plant. Corrective actions—including the installation of Pressure-Independent Control Valves (PICVs), differential pressure sensor relocation to the critical index coil, and system re-balancing, restored design temperature differentials (Delta T = 6.7C/12F), reduced specific plant power consumption from 0.85 kW/ton to 0.66 kW/ton, and improved overall plant Coefficient of Performance (COP) by 28.2%. Keywords: HVAC, Testing Adjusting Balancing (TAB), Low Delta-T Syndrome, Chilled Water Plant Efficiency, Pressure Independent Control Valves (PICV), District Cooling, NEBB, Commissioning