The challenge
A South Carolina hospital runs a 2,360 TR chilled water plant: three 1,702 kWr chillers, one 3,194 kWr chiller and five cooling towers. Cooling has to stay reliable around the clock for patient care.
Before optimization the plant started its chillers 28.6 times a month on average, each start ran for 31 hours, and the plant logged 11 short cycles a year. Each start drives locked-rotor current through the motor windings, thermally cycles the compressor and interrupts oil return, so fewer, longer runs mean less wear on the machines.
Half the starts, three times the runtime per start, and no short cycles in the reporting period.
Site profile
Verified results
Mechanical health after full optimization
Starts and run hours come from the BMS chiller status trends, normalized to monthly rates. The baseline covers January 2024 to July 2025, all seasons. The reporting period covers the first two months of full optimization, July and August 2026.
| Plant | Before | After | Change |
|---|---|---|---|
| Chiller starts per month | 28.6 | 14.5 | 49% fewer |
| Runtime per start (hours) | 31 | 101 | 3.3× longer |
| Short cycles | 11 a year | 0 in the reporting period | Eliminated |
| Chiller | Starts per month, before | After | Change | Hours per start, before | After |
|---|---|---|---|---|---|
| Chiller 1 | 12.7 | 7.5 | −41% | 18 | 61 |
| Chiller 2 | 8.1 | 3.5 | −57% | 30 | 69 |
| Chiller 3 | 3.7 | 3.0 | −19% | 23 | 21 |
| Chiller 4 | 4.2 | 0.5 | −88% | 79 | 1,408 |
Plant energy from the condenser water reset
| Reporting period, 28 days | Adjusted baseline | Actual | Saved |
|---|---|---|---|
| Chilled water plant energy (kWh) | 432,058 | 390,351 | 41,707 (9.65%) |
| Emissions (kgCO2e) | 115,360 | 104,224 | 11,136 (9.65%) |
Preliminary M&V of the condenser water reset alone, from 20 August to 17 September 2025, using a regression of daily plant energy against cooling load and system lift (IPMVP). Energy M&V of the full optimization will follow once it has a longer reporting period.
The Exergenics approach
Two stages, both in the existing BMS
Condenser water reset first
A dynamic condenser water temperature reset, calculated from wet bulb and cooling load, went live in August 2025. Exergenics confirmed remotely that the plant tracked the new setpoints.
Full plant optimization
Chiller sequencing and stage up and stage down demand setpoints followed in July 2026. They keep the right chillers on line for the measured load, so machines run longer and start less.
Programmed by the site's contractor
Both stages were issued as functional descriptions and programmed into the existing BMS by the site's controls contractor. No hardware was added and every existing safety and interlock stayed in place.
Measure energy and mechanical health
Energy was verified against an adjusted baseline. Starts, run hours and short cycles were counted from the BMS chiller status trends.