Multiple Chiller Sequence Control Imbalance — Operating Hours Rotation Failure

Question

Accepted Answer

BMS lacks rotation logic based on accumulated operating hours. Check: Check each chiller accumulated operating hours — if deviation exceeds 200 hours, rotation not being performed. Verify in BMS sequence logic whether chiller #1 is always set as fixed lead unit What to do: Implement automatic rotation logic in BMS based on accumulated hours — auto-switch lead unit when difference exceeds 200 hours. Without BMS, manually switch lead unit monthly and reset operating hour records Chilled water setpoint temperature variance between chillers — parallel load imbalance. Check: Measure actual supply temperature of each chiller — if there is variance like #1 at 5°C and #2 at 6°C, load concentrates on the lower-temperature chiller. Check header branch valve openings — verify all chiller supply and return valves at 100% opening What to do: Unify chilled water supply temperature setpoint across all chillers — keep supply temp variance within ±0.5°C during parallel operation. Reset sequence thresholds: load ≥75% → start next chiller; load ≤45% → stop one unit (30% hysteresis band). After rotation, confirm previous unit current = 0 A before proceeding

Multiple Chiller Sequence Control Imbalance — Operating Hours Rotation Failure

Likely causes

BMS lacks rotation logic based on accumulated operating hours

Chilled water setpoint temperature variance between chillers — parallel load imbalance

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