CASE09 · Manufacturing · Chiller systems
Building monthly chiller operating plans from COP and seasonal demand
Hourly operating records support efficient-unit priority, monthly staging and chilled-water setpoints for 5°C and 12°C systems. Pump conditions are standardized so that equipment performance can be compared fairly.
01 · CASE ANALYSIS
Operating challenge
Outside the summer peak, the plant had operating capacity above the calculated requirement. Chillers of the same capacity showed different COPs, making performance-based sequencing preferable to an unexamined rotation schedule.
Different chilled-water outlet temperatures and pump flows made direct equipment comparison difficult. Cleanroom dehumidification during humid weather also limited how far water temperatures could be raised.
02 · CASE ANALYSIS
Data and comparison method
The analysis combined equipment specifications, hourly COP, monthly required and actual unit counts, outlet temperatures, pump power and water flows for the 5°C and 12°C systems.
COP is cooling output divided by chiller electrical input. The report proposes standardizing chilled-water flow to an AHRI-equivalent reference of 545 m³/h for a 1,000 RT machine, with cooling-water conditions also aligned between running units. This is the source report’s comparison reference, not a substitute for equipment-specific limits.
| Criterion | Source approach |
|---|---|
| Equipment priority | Rank chillers by monthly COP within each system |
| Staging | Compare actual units with cooling-load-based required units |
| Flow reference | 1,000 RT → 545 m³/h chilled-water flow |
| Humidity constraint | Preserve cleanroom dehumidification performance |
03 · CASE ANALYSIS
Monthly operating strategy
Select higher-COP units first, add capacity according to required load and use seasonal setpoints. The 5°C system plan ranges from roughly 2–3 units in low-load periods to a maximum range of 6–12 in peak summer periods; the 12°C system uses roughly 2–3 and 5–6, respectively.
For the 5°C system, the proposed outlet range is about 5.5–7.0°C by season; the 12°C system uses approximately 12°C. Humid-season cleanroom requirements take priority.
04 · CASE ANALYSIS
Evidence and verification
The source gives a general operating rule that a 1°C increase in outlet setpoint may reduce chiller energy by approximately 2%. That rule is not a measured saving for this project.
The report does not provide confirmed annual savings after implementation. Validate the plan using cooling load, total cooling-system electricity, weather, production and cleanroom conditions.
| System | Low-load units | Summer units | Outlet setpoint |
|---|---|---|---|
| 5°C circuit | Approximately 2–3 | Peak range approximately 6–12 | Approximately 5.5–7.0°C seasonally |
| 12°C circuit | Approximately 2–3 | Approximately 5–6 | Approximately 12°C |
05 · CASE ANALYSIS
Engineering lesson
Staging, setpoints and pump conditions should be coordinated. Comparing chiller COP without comparable water and load conditions can produce misleading operating priorities.
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