Low Delta-T Syndrome Plant Profile Mitigation
This results in secondary pumps running at 100% capacity while chillers remain unloaded (unable to reach their peak design capacity). The chillers are effectively starved of BTUs while the pumps waste thousands of dollars in electrical energy merely circulating cold water. The root causes are typically degraded AHU coils, dirty filters, improperly tuned PID control valves, or legacy 3-way bypass valves.
Mitigation Strategies
Correcting Low ΔT rarely involves the chillers themselves; the problem lives in the building loop. The goal is to slow the water down so it has time to absorb heat from the air passing over the AHU coils.
| Root Cause | Mitigation Tactic |
|---|---|
| Dirty AHU Coils | Clean coils chemically. Air cannot transfer heat to the water if the aluminum fins are insulated by dust and biofilm. |
| High Pump Pressure | Lower the Differential Pressure (DP) setpoint on the VFD drives. Stop forcing water through valves faster than it can absorb heat. |
| 3-Way Valves | Cap the bypass ports to convert 3-way valves to 2-way valves. This forces water through the coil instead of bypassing directly back to the return line. |
Diagnostic Gateway Challenge
A chilled water plant is running at full capacity on its pumps (60Hz), but the return water is only 47°F (Supply is 42°F). The chillers are only loaded to 45% capacity. The building automation system is alarming for “High Space Temperatures.” What is the most effective first step?