Services / Specialist Controls Optimisation

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Chiller Plant Optimisation, Implemented in the BMS You Already Own

Specialist Controls Optimisation is where the energy savings come from. A calibrated digital twin finds the setpoints that run your plant at its best, forecasts the saving, and hands the strategy to your BMS contractor in a format they already use.

CALIBRATED TWINCT-1CT-2CT-3CONDENSER WATERChiller 1Chiller 2Chiller 3kWr, kWkWr, kWkWr, kWCHILLED WATERFIELD DEMAND, kWr1Physics engine2Machine learning3Predictive control4M&V baselineWET BULB, °C
5–35%
less chilled water plant energy. Published engagements sit between 6.8% and 33.4%, each measured to IPMVP Option B.
10–15%
peak demand reduction, from staging on field demand rather than on chiller loading.
~18 mo
average payback. The full range across published sites is 6–24 months.
None
new hardware, new technicians or new software on site. Your incumbent controls contractor implements.
Setup
About a month. Calibrated twin in weeks 6–10
Implemented by
Your incumbent BMS contractor, outside normal hours
Verified
IPMVP Option B at month 12, then every year
Output
A functional description in industry-standard format
On this page
Where the savings come fromThe six control strategiesStaged on field demandWhat does not changeMore than energyOptionsResultsFAQ

Where the energy savings come from

Chillers, pumps and cooling towers typically take 25–50% of a commercial building’s electricity. Every machine has its own efficiency profile, and each depends on what the others are doing. That is hard for people to optimise by hand.

From the millions of possible setpoint combinations, the optimisation engine finds the one that maximises efficiency and mechanical performance for every load, weather and stage. Once calibration is complete, a multi-stage optimisation loop solves the plant as one system: the load balancer sets the split between machines, the staging optimiser sets when they come on and off, and the condenser water loop is solved for lowest total power rather than lowest chiller power.

The six control strategies

Every strategy is a setpoint calculation the BMS can run and your team can read. Most engagements implement three or four of the six. Which ones, and in what order, follows the plant’s own data.

Dynamic condenser water temperature reset

Setpoint calculated from chiller status, field demand and wet-bulb temperature, as an approach above wet bulb that changes with the stage and the load. Reset minutely (adjustable) between the minimum and maximum constraints set by the client or the incumbent, rate-limited to 0.2 °C per minute. Chiller power rises with condenser water temperature while tower fan and pump power fall; the setpoint sits at the bottom of that total.

Dynamic condenser water flow reset

Setpoint calculated as a function of chiller load, modulating between the minimum and maximum flow constraints, rate-limited to 1 L/s per minute. Targets the condenser water pump share of plant energy, typically 10–15%.

Chiller sequencing strategy

Order of operation of available chillers and groups of identical chillers. Where machines differ in design, fixed speed against VSD for example, the sequence falls out of their two performance surfaces rather than a rotation rule. Improves runtime per cycle, short cycling, starts and stops, and runtime balance between low-load and high-load chillers.

Chiller stage up and stage down demand setpoints

Staging on field demand (kWr), not chiller loading percentage. Stage-up and stage-down bands overlap: that overlap is the hysteresis that stops hunting, with a stabilisation delay of 15 minutes to stage up and 20 minutes to stage down (adjustable). Runtime delay timers, minimum decoupler flow, lead/lag rotation and every other chiller safety and reliability measure stay where they are.

Dynamic chiller load balancing

Where chillers on a common header have different efficiency curves, no fixed split is right across the year. The load balancer publishes the split as a lookup table against field demand and wet bulb, so the BMS reads it rather than calculates it.

Dynamic chilled water temperature reset

Supply temperature reset against field demand and ambient conditions, within limits that hold comfort and dehumidification. Where the M&V boundary requires chilled water temperature to the field to be held, this strategy is simulated for its energy saving and reported rather than implemented.

Staged on field demand, not chiller loading

Setpoints are calculated from variables already measured or calculated in the BMS. No new instrumentation is assumed.

Variable
Unit
Definition
Field demand
kWr
Instantaneous cooling delivered to the field. The primary control variable: staging, sequencing and the condenser water loop all respond to it rather than to chiller loading percentage.
Wet-bulb temperature
°C
Outside ambient wet bulb, measured, or calculated from dry-bulb temperature and relative humidity.
Chiller status
on / off
Enabled status of each chiller, which determines the current stage of operation.
Chiller load
kWr
Instantaneous cooling output of each chiller.
kWr = field L/s × (return °C − supply °C) × 4.187

Field demand from common supply and return temperature and flow, the most reliable of the three available methods.

What does not change

All existing hardware and software is retained: servers, controllers, network, panels, valves, actuators, sensors and the BMS application itself. Nothing is installed.

All existing safety mechanisms, interlocks and control strategies outside the chilled water plant stay in place unless the functional description states otherwise.

Implementation is by the incumbent controls technician or an approved agent, tested offsite and commissioned outside normal hours. Exergenics does not write to the BMS.

The strategy is published as a site-specific functional description in industry-standard format. It is yours to keep.

More than energy

Reduce base building energy

5–35% of chilled water plant energy, with published sites between 6.8% and 33.4%. Verified against a calibrated baseline, not estimated from a benchmark.

Reduce peak demand

10–15% lower peak, from staging on field demand and holding the condenser water loop at its lowest total power rather than its lowest chiller power.

Cut emissions and report them

Annual tCO₂e avoided, measured to IPMVP Option B and suitable for sustainability reporting and utility submission.

Extend the useful life of plant

Fewer starts and stops, fewer short cycles, longer runtime per cycle, and runtime balanced across machines. Mechanical performance is baselined and reported alongside energy.

Options

Each option includes the one before it, and every one includes a functional description for your BMS contractor.

Dynamic Condenser Water Reset
The highest-payback single control. Requires plant digitisation.
Staging Optimisation
Chiller staging on field demand, sequencing and load balancing, with pump and fan modulation.
Full Optimisation
The complete recommendation set, with the what-if analyser and first-year M&V at month 12, IPMVP Option B.

Priced per kilowatt of refrigeration (kWr) of installed plant capacity. Request a price list

Controls Overview, September 2026

The strategies, the plant variables they are calculated from, and the constraints that stay in place. Written for the BMS technician and the consulting engineer.

Download PDF

Verified plant energy savings

33.4%
Sydney Airport, Terminal 1. Plant already at 0.56 kW/ton before optimisation.
12.3%
Hotel and casino. 658 rooms, 5,600 TR plant.
11.8%
University campus, California.
6.8%
Hospital, Queensland. No disruption to clinical areas.

All figures measured to IPMVP Option B against a weather and load adjusted baseline, with no new hardware. Read the case studies

Frequently asked questions

How much energy can chiller plant optimisation save?

5–35% of chilled water plant energy. Published sites range from 6.8% to 33.4%, each verified to IPMVP Option B.

Do we need new hardware or a new controller?

No. The work is software only and air-gapped from plant control. Nothing is installed.

Who implements the strategy?

Your incumbent BMS contractor, in the existing BMS, outside normal hours, with every safety and interlock retained. Exergenics witnesses remotely.

Is the strategy a black box?

No. Setpoints are published as readable logic your team can interrogate, not a controller in a cabinet.

Related services

Start with a Feasibility Study

A desktop forecast from your plant’s own BMS data: data gap analysis, a plant health check and a Plant Potential business case. Credited in full against any option purchased within 90 days.

Priced per kilowatt of refrigeration (kWr) of installed plant capacity. Request a price list