Most chiller energy-saving measures require no new equipment. They come down to bringing the system back to its design conditions — something the system drifts away from after a few years of operation without anyone noticing.
The general principle: reduce the temperature lift
The efficiency of a refrigeration system depends on the gap between the evaporating temperature and the condensing temperature. The wider the gap, the harder the compressor has to work.
From that, there are only two directions for saving energy: raise the evaporating temperature to just what is needed, and lower the condensing temperature as far as possible. Every specific measure below is a variation of these two directions.
Group 1 — Do it now, no cost
- Review the leaving water temperature setpoint. If the production process only needs a certain level and the system is running below it, that is wasted energy every hour. This is the most effective and cheapest measure.
- Switch off units that are not needed. On multi-unit systems, run only as many units as the actual load requires instead of running them all at part load.
- Check the running schedule. Systems still running outside production hours is far more common than most people think.
- Seal the cooled area. Open doors, gaps and warm air infiltration all increase the load.
Group 2 — Maintenance, low cost, clear results
- Clean the air-cooled or water-cooled condenser. Dirt and scale push the condensing pressure up, driving energy consumption with it. This is the item that gives the clearest result per dong spent.
- Treat the condenser water to limit scale from forming again — cleaning once without treating the water and it will be back to the same state a few months later.
- Clean the cooling tower fill and nozzles, check the fan and belts.
- Purge non-condensable gases from the system.
- Check the refrigerant charge. A refrigerant shortfall reduces cooling capacity, so the system has to run longer for the same result.
- Clean the water strainers and check the pumps, ensuring flow matches the design.
Group 3 — Requires investment, pays back over time
- VFDs for pumps and fans. Pumps running fixed at design flow while the actual load is lower is the most frequent waste in a chiller system.
- Thermal storage tanks for systems with fluctuating loads, helping the compressor run steadily instead of cycling on and off constantly.
- A central control system that automatically stages the number of units running according to load, instead of manual operation.
- Re-insulate the pipework if the old layer has degraded, opened up or is sweating.
- Waste heat recovery from the condenser to supply hot water for other needs in the plant.
Where to start: measure before you fix
Do not invest before you know where the problem is. Four parameters to track first:
- Condensing pressure and temperature against the design values — a high deviation means the problem is on the heat rejection side
- Evaporating pressure and temperature — an abnormally low deviation may be caused by low refrigerant charge or a dirty coil
- Compressor current in steady-state operation, against the rated figures
- Water temperature difference in and out on both the load side and the heat rejection side — this tells you whether the flow is correct
Comparing these parameters with the figures recorded at commissioning is the fastest way to see how far the system has drifted. This is also why you should record the initial operating parameters right at handover.
Common mistakes when trying to save energy
- Lowering the leaving water temperature to “run faster”. The opposite is true — every extra degree lower reduces efficiency.
- Cleaning only, without treating the water. The scale comes back after a few months.
- Investing in VFDs while the condenser is dirty. Fix the easy and cheap part first, invest later.
- Switching off pumps to save energy. Insufficient flow degrades heat exchange, and the compressor consumes more energy than the pump saves.
The minimum maintenance schedule to keep
The specific frequency depends on the installation environment and operating hours, so it should be agreed with the maintenance provider. In principle, the items that directly affect energy consumption need regular checks: heat exchange surfaces, cooling water quality, refrigerant charge, and the basic operating parameters.
Tan Long provides scheduled maintenance for chiller systems and industrial refrigeration systems in factories.
Besides operational optimisation, some plants also reduce their grid load with solar-powered cold storage.
Frequently asked questions about chiller energy saving
Which measure is the most effective at no cost?
Review the leaving water temperature setpoint. If the production process only needs a certain level and the system is running below it, that is wasted energy every operating hour — and it can be fixed immediately with a setting change.
Why does cleaning the condenser save so much energy?
Because dirt and scale obstruct heat exchange, pushing the condensing pressure higher. The compressor has to work across a larger pressure difference, so it consumes more energy. This is the item that gives the clearest result per dong spent.
Why does it get dirty again a few months after cleaning?
Because it was only cleaned, without treating the cooling water. Water evaporating continuously at the tower gradually concentrates the minerals and re-forms the scale. The water has to be treated for the cleaning result to hold.
Does switching off some pumps save energy?
No. Insufficient flow degrades heat exchange, and the compressor consumes far more energy than the pump saves. The correct solution is to fit a VFD so the pump runs according to the actual load.
Which parameters should be tracked to know the system is degrading?
Condensing pressure and temperature, evaporating pressure and temperature, compressor current at steady state, and the water temperature difference in and out on both the load side and the heat rejection side — compared with the figures recorded at commissioning.
Should we invest in VFDs first or do maintenance first?
Maintenance first. Investing in VFDs while the condenser is dirty means fixing the expensive part while the cheap part is still faulty. Clean the heat exchange surfaces and treat the water first, then measure again, and only then decide on the investment.
Related pages
- Chiller maintenance: procedure and warning signs
- Chiller cooling tower
- What COP is and what makes actual COP fall
- High discharge pressure faults: causes and remedies
- Water-cooled or air-cooled chillers
- Refrigeration system maintenance services
Is your business in need of a survey, upgrade, or new design for your industrial refrigeration system?
With over 18 years of practical experience leading more than 29 major national projects, Tan Long's team of HVAC engineers is committed to providing accurate thermal load calculations, optimizing the COP efficiency coefficient, switching between natural refrigerants NH3/CO2, and saving 20–30% in operating electricity costs.
Engineer Nguyen Toan Thinh (Technical Director)
With over 18 years of practical experience in directing, consulting, designing, and constructing heavy industrial refrigeration systems, ASRS automated warehouses, and IQF freezing systems across more than 29 major national projects.
