Chiller and Cooling System Monitoring
In a hotel, a hospital or a shopping centre, cooling is the largest line on the summer electricity bill. Yet on most sites no number is ever produced that says how efficiently the chiller ran that day.
Live
The chiller plant on one card
Cooling load, power drawn and COP at the same moment. System COP includes pumps and the tower; machine COP covers the chiller alone. The gap between them answers where the loss is.
The three figures below the card are read together: if power does not fall as the load falls, the machine is inefficient at part load; if kW/ton rises, the condenser side is examined. Values refresh every minute, and the day’s course is kept in the card’s own chart.
- System and machine COP, separately
- kW/ton and live cost
- Outdoor wet-bulb temperature alongside
Cooling load is calculated from flow and return water temperatures and flow rate; power is read from each chiller’s own analyser. Once pump and tower power are added to the system, the gap between machine COP and system COP shows the share of the auxiliaries.
Chiller Plant
live · sample site4,6COP
expected 4.4 · 5.0
System COP · outdoor 26 °C, wet bulb 21 °C
Weather
COP cannot be compared without the weather
As the wet-bulb temperature rises, the same machine’s COP falls. To compare two days the weather is corrected first; only then is it clear whether the difference came from the machine or the air.
- Expected COP band, weather-corrected
- Hours below the band are flagged
- Real hourly weather data
The expected band is built from the site’s own history: the COP values reached before at the same wet-bulb temperature. Weather data is hourly and real; if the hours below the band cluster at a certain time of day, the problem is found by looking there.
COP and Weather
wet bulb · expected bandSchematic: band from the site's own history; weather data hourly.
Fleet
When the machines are compared with each other
Same load, same weather, different COP. Sequencing and load sharing are read from this table: which chiller should lead, which one is asking for maintenance.
The table is fed by each chiller’s own meter; the load column is scaled to machine capacity. A COP difference at the same weather and load belongs to the machine: maintenance history, condenser fouling and refrigerant charge are the first places to look.
- Sequencing advice: the efficient machine leads
- Time spent at part load reported separately
- COP before and after maintenance compared
Chiller Fleet
today · 14:00 · against the expected band- Chiller 1 · load 82% 4.90COP inside the band
- Chiller 2 · load 61% 3.70COP 18% below the band · maintenance
- Chiller 3 · load 35% 4.40COP at the edge
- Chiller 4 · load 48% 4.60COP inside the band
Tower
The chiller may not be the culprit
If condenser water arrives warm, the tower sets the ceiling; whatever the chiller does, it cannot lift its COP. Approach temperature and condenser ΔT are watched together.
- Tower approach (tower outlet minus wet bulb)
- Condenser and evaporator ΔT
- Sequencing advice: which machine at which load
Tower approach and condenser inlet temperature are watched continuously; the split of the deviation across components is calculated every week. “The chiller is inefficient” becomes a fixable finding such as “tower approach 6 K, condenser ΔT low”.
Where the Loss Is
last 7 days · share of deviationWhat we measure, and from where
Measurement plate
- Electrical power
- kW
- Chiller, pumps and tower measured separately
- Chilled water
- °C · m³/h
- Flow, return and volumetric flow rate
- Condenser circuit
- °C · m³/h
- Inlet, outlet and flow rate
- Cooling load
- kW
- Derived · flow × ΔT
- COP
- kWth/kWe
- Derived · machine and system reported apart
- Ambient
- °C · %RH
- Hourly meteorology · wet bulb derived
- Tower approach
- °C
- Tower outlet − wet bulb
Where a measurement point cannot be added, the datasheet curve is used as the basis and that is labelled explicitly. Measured and derived are never presented as the same thing.
Common questions
Our BMS already monitors the chillers. What would change?
A BMS manages state: start, stop, hold a setpoint, raise an alarm. It does not calculate efficiency, because that would require measuring the cooling load, flow and ΔT, and ratioing it against electrical power. Most BMS installations have no flow meter. Where we can take data from your BMS we will; we add the measurement that is missing.
The manufacturer already publishes a COP. Why measure it?
A datasheet COP holds at the design condition, on a new machine. Yours runs at a particular part load, at a particular condenser temperature, with however many years on it. The difference between the two can run to tens of percent. We put the measured COP alongside the datasheet curve and show the gap.
Does installation require work on the chiller itself?
Nothing is opened up. The measurements needed sit on the pipework and in the electrical panel: a flow meter, temperature sensors and a power analyser. Where existing analysers or BMS points are available they are read instead. If the chiller's own control panel exposes data, that can be taken too.
We have an absorption machine. Can it be compared with an electric chiller?
It cannot, and we do not. An absorption machine's thermal COP is calculated against heat input; an electric chiller's against electricity. They are not on the same scale, and reading them side by side misleads. The panel reports them separately and carries that warning above the screen.
Does this support ISO 50001 or ESOS?
It supports both, without being either. For ISO 50001 the hard part is normally continuous measurement of significant energy uses and a baseline you can defend, that is what this provides. For ESOS the assessment itself must be signed off by an approved lead assessor, but the twelve months of data behind it, and the progress reporting the scheme now expects against an action plan, come from the same measurement layer. The Phase 4 compliance deadline is 5 December 2027.
Let us measure what is happening on your site.
In a one-hour call we look at your existing setup and set out exactly which measurement points are needed and what you would be able to see.