Chiller systems are important equipment in commercial buildings, shopping centres and factories with cooling requirements. Electricity consumption comes not only from the Chiller itself but also from chilled water pumps, condenser water pumps and cooling tower fans.
Therefore, to reduce operating costs, businesses need to assess the entire system rather than focus solely on the chiller. HRT shares solutions to help reduce Chiller system electricity consumption based on operating conditions, equipment efficiency and actual energy management capabilities.
Why do Chiller systems consume so much electricity?
Declining Chiller efficiency
Chiller electricity consumption depends on the cooling load, heat rejection conditions, water temperatures and equipment condition. When heat transfer surfaces become fouled or operating conditions are unsuitable, the unit may require more electricity to meet the same cooling demand.
Two commonly used efficiency indicators are COP and kW/ton. COP represents the ratio of cooling capacity to electrical input power; under the same assessment conditions, a higher COP generally indicates better efficiency. The kW/ton indicator represents the electrical power required to produce one unit of cooling capacity, so a lower value generally indicates better efficiency.
When comparing efficiency, the actual load, ambient conditions and measurement scope must be considered. A single COP or kW/ton value should not be the sole basis for determining whether a unit is operating well or poorly.
Inefficient electricity consumption by chilled water and condenser water pumps
Chilled water and condenser water pumps may operate for long periods. If flow rates or pressures are maintained above actual requirements, the system may consume electricity unnecessarily.
However, reducing flow is not always beneficial. Water flow must meet the requirements of the Chiller, heat exchangers and distribution system. Adjustments must be based on equipment characteristics and hydraulic design.
Inefficient cooling tower operation
For water-cooled Chillers, the cooling tower directly affects the condenser's heat rejection conditions. Dirty heat transfer surfaces, uneven water distribution or unsuitable fan operation can reduce heat rejection effectiveness.
When heat rejection capability declines, the Chiller may have to operate under less favourable conditions. Therefore, inspecting the cooling tower is an important part of assessing electricity consumption across the entire system.
Operating modes that do not match the cooling load
If the Chiller and auxiliary equipment operate on a fixed schedule while cooling demand changes over time, the system may consume more electricity than necessary. Keeping too much equipment running at low loads and using unsuitable temperature settings both need to be checked.
Read More VRV Industrial Air Conditioning
Read More Packaged Industrial Air Conditioning
Read More Chiller Industrial Air Conditioning
How to reduce Chiller system electricity consumption
Optimise operation according to the actual cooling load
Businesses need to review cooling demand by hour, area and production process. Based on this data, the engineering team can adjust operating schedules, the number of Chillers to run and equipment start-up times.
For systems with multiple Chillers, the combination of units to operate must be selected based on the cooling load and each unit's efficiency at different load levels. The largest-capacity unit should not automatically be run first, nor should the load be distributed equally among all units in every situation.
The optimisation process must ensure that the system continues to meet temperature, humidity and process requirements. For areas requiring continuous cooling, changes to operating schedules must be carefully assessed to avoid affecting facility operations.
Adjust the chilled water supply temperature appropriately
The chilled water supply temperature affects Chiller efficiency and the cooling capability of terminal units. Under certain conditions, raising the chilled water supply temperature within permissible limits can reduce the unit's compression work and electricity consumption.
However, the temperature should not be raised arbitrarily. Chilled water must meet the heat transfer requirements of AHUs, FCUs or cooling equipment in the factory. If the water temperature is not low enough, the system may fail to meet cooling or dehumidification requirements.
The appropriate approach is to monitor the cooling load and supply and return water temperatures, then make gradual adjustments in accordance with the design and the manufacturer's guidance. Effectiveness must be verified using operating data from before and after the adjustments.
Optimise condenser water temperature and cooling tower operation
For water-cooled Chillers, the temperature of the water entering the condenser affects the compressor's operating conditions. Within the permissible operating range, a lower condenser water temperature can help improve Chiller efficiency.
However, lowering the condenser water temperature does not mean that total electricity consumption will always decrease. Cooling tower fans and condenser water pumps may consume additional electricity if they have to work harder to achieve a lower temperature.
Businesses need to consider the electricity consumption of the Chiller, pumps and tower fans together. Control strategies should be based on the cooling load, ambient conditions and equipment operating limits, rather than setting a fixed temperature for all times.
Adjust flow rates and use variable frequency drives for pumps
Variable frequency drives allow motor speeds to be adjusted according to operating requirements. For pump systems with variable loads and suitable control conditions, this solution can help reduce electricity consumption compared with maintaining a fixed speed in all situations.
Before installing or adjusting a variable frequency drive, pump characteristics, required flow rates, differential pressure and valve control capabilities must be checked. In particular, the water flow through the Chiller must not fall below the limit specified by the manufacturer.
Pump speed should not be reduced solely to save electricity without first assessing the impact on heat exchange and water distribution. Adjustments must follow the hydraulic design and actual operating parameters.
Coordinating the number and operating sequence of multiple Chillers
In systems with multiple units, coordinating equipment according to cooling load can help prevent units from operating at unsuitable load levels. The controller must consider each unit's efficiency at different loads, auxiliary power consumption and operating limits before deciding to start or stop equipment.
When the cooling load decreases, the system may not need to keep all Chillers running. However, the decision to stop a unit must consider the remaining cooling capacity, the ability to meet the load and redundancy requirements.
Effective coordination should aim to reduce the total electricity consumption of the entire system while maintaining cooling capability. Optimisation should not focus solely on the electricity consumed by the Chiller while overlooking the electricity consumed by pumps and cooling towers.
Maintaining heat exchangers and cooling towers
Fouled heat transfer surfaces can reduce heat transfer efficiency and affect equipment operating conditions. Businesses therefore need to inspect the condition of condensers, evaporators and cooling towers in accordance with the manufacturer's instructions.
For cooling towers, attention should be paid to heat transfer surfaces, the water distribution system, fans and scale buildup. Water quality also needs to be appropriately controlled to limit scaling and corrosion in the system.
Cleaning and maintenance frequency should be based on water quality, operating conditions and inspection results. A single fixed schedule should not be applied to every facility when actual conditions differ.
Inspecting AHUs, FCUs, valves and sensors
Overall system efficiency also depends on terminal equipment and control capability. Dirty filters, malfunctioning control valves or inaccurate sensors can cause the system to distribute cooling in a way that does not match demand.
Technicians need to check air filter condition, water flow, valve operation and sensor reliability. If discrepancies are found, they must be addressed according to the actual cause rather than replacing components arbitrarily.
Inspecting terminal equipment helps assess the relationship between cooling demand and Chiller operation, thereby identifying adjustments needed to limit unnecessary energy consumption.
Monitoring electricity consumption and optimising the control system
To manage electricity consumption effectively, businesses should monitor electrical power, electricity consumption, cooling load, supply – return water temperatures and equipment operating status. If a BMS or central controller is available, the data can be used to review operating schedules and adjust parameters according to actual conditions.
For facilities with suitable conditions, businesses can also assess solutions that utilise naturally available cooling, such as free cooling or a waterside economizer. However, applicability depends on the climate, system configuration and water temperature requirements. This is not a default solution for every Chiller system.
Read More R-Refresher HVAC: A Solution for Improving System Efficiency
How to assess the electricity-saving effectiveness of a Chiller system
Measuring electricity consumption and cooling load before optimisation
Before implementing a solution, the measurement scope must be defined. If only the Chiller is assessed, the electricity data will not fully reflect the electricity consumed by pumps and cooling towers. If the entire Chiller Plant is assessed, the measurement scope must include the auxiliary equipment within the system under consideration.
In addition to electricity consumption, cooling load and operating condition data must be collected as a basis for comparison. Without baseline data, businesses will find it difficult to determine whether a solution is truly effective.
Comparing efficiency under equivalent conditions
COP and kW/ton can be used to assess Chiller efficiency when sufficient cooling capacity and electrical power data are available. When comparing performance before and after optimisation, cooling load, ambient conditions and operating time must be considered.
If measurement conditions differ significantly, electricity consumption before and after optimisation cannot be compared directly to draw conclusions about savings. For systems with fluctuating loads, data should be assessed over appropriate periods, taking differences in cooling demand into account.
Ensuring the system still meets cooling requirements
Reducing electricity consumption is not the only objective. After changing parameters, businesses need to confirm that the system still meets temperature, humidity and process load requirements. If electricity consumption decreases but cooling performance does not meet requirements, the optimisation approach has not met the operating objectives.
Read More Criteria for Selecting a Reputable VRV Installation Contractor
Mistakes to avoid when reducing Chiller electricity consumption
A common mistake is raising the chilled water temperature or lowering the condenser water temperature without monitoring the impact on the entire system. These adjustments can improve efficiency under certain conditions, but they must be assessed alongside auxiliary equipment electricity consumption and cooling requirements.
Businesses should also not reduce pump flow without first confirming the Chiller's operating limits. Similarly, changing control settings or replacing components without inspection data may fail to address the actual cause.
In addition, a fixed electricity-saving percentage should not be promised for every system. Effectiveness depends on the existing condition of the equipment, cooling load, ambient conditions and the scope of the solutions implemented.
How does HRT support HVAC systems?
HRT provides services including consultancy, site surveys, design, equipment selection, installation, acceptance, warranty and maintenance for HVAC systems.
For Chiller systems, assessing operating conditions, selecting suitable equipment and performing technically correct maintenance are factors that need to be considered in system management. The specific approach must be based on the facility's existing condition, cooling requirements and technical assessment results; electricity savings should not be determined before suitable data are available.
Read More How to Maintain a VRV Air Conditioning System Correctly
Conclusion
An effective way to reduce the electricity consumption of a Chiller system is to assess the entire system, from the Chiller to chilled water pumps, condenser water pumps, cooling towers and control equipment. Solutions must be selected according to the cooling load, operating conditions and equipment technical limits.
Businesses should begin by collecting electricity consumption data, inspecting existing conditions and identifying areas for improvement. After implementation, measurements must be repeated to verify effectiveness while ensuring that the system continues to fully meet the facility's cooling requirements.
Contact information
HRT Air Conditioning and Ventilation Company
Address: No. 9TT7 Foresa 7A Street, Tasco Ecological Urban Area, Xuân Phương Ward, Hà Nội City, Vietnam
Hotline: 0916 181 080
Email: CEO@hrt.vn
Frequently asked questions about reducing Chiller system electricity consumption
Can Chiller electricity consumption be reduced without replacing the unit?
Optimising operating schedules, adjusting parameters, inspecting auxiliary equipment and carrying out maintenance can be considered before deciding to replace the unit. The effectiveness depends on the system's condition and the results of an on-site assessment.
Does increasing the chilled water supply temperature help save electricity?
Under certain conditions, increasing the chilled water supply temperature within permissible limits can reduce Chiller electricity consumption. However, the system's cooling and dehumidification capabilities must be maintained, and total electricity consumption must also be assessed.
Is installing a variable frequency drive for a Chiller pump effective?
A variable frequency drive can help reduce electricity consumption when the required flow rate varies and the system is suitable for speed control. Before implementation, the pump characteristics, minimum flow rate and Chiller operating requirements must be checked.
Should Chiller efficiency be assessed using COP or kW/ton?
Both metrics can be used. A higher COP generally indicates better efficiency, while a lower kW/ton generally indicates lower electricity consumption per unit of cooling capacity. Comparisons must use equivalent measurement boundaries and operating conditions.
How often should a Chiller system be inspected?
Operating parameters should be monitored regularly in accordance with the facility's management procedures. The specific maintenance schedule should be based on the manufacturer's instructions, water quality, operating conditions and equipment condition.