Chillers are the heart of a commercial building’s HVAC system, providing Chilled Water (ChW) occupant comfort, process cooling and outside air system.  Being among the most energy intensive and capital expensive assets in any facility, implementing a structured preventative maintenance schedule is critical to ensuring operational efficiency, compliance, and asset longevity.  Different applications, location, building contractors and HVAC system types will call for different chiller types, the most common are detailed below:

Air-Cooled Chillers: Rejecting heat using ambient air driven across condenser coils by mechanical fans.

• Best For: Small to medium commercial properties, locations with water scarcity, or facilities seeking lower initial capital and installation complexity.
• Key Advantage: Fewer components (no cooling towers or condenser water pumps), reducing structural space requirements.
  

Water-Cooled Chillers: Utilise an external cooling tower and condenser water system to reject heat from the refrigerant.

• Best For: Large-scale commercial high-rises, hospitals, and campus-wide district cooling systems.
• Key Advantage: Significantly higher thermodynamic efficiency (kW/kWr) compared to air-cooled models, translating to lower

Within these systems, the method of mechanical compression further defines the equipment: long-term operational energy bills.

• Centrifugal Chillers: Utilise a rotating impeller; highly efficient at high loads in large water-cooled systems.
• Screw / Scroll Chillers: Utilise interlocking helical rotors or orbiting scrolls; commonly found in small-to-medium air-cooled and water-cooled installations due to reliable part-load performance.
  

What are the Key Maintenance Tasks for Different Chiller Types

To prevent catastrophic compressor failure and maintain optimal energy performance, maintenance activities should be structured within a clearly defined, frequency-based programme. A disciplined maintenance regime ensures that deterioration is identified early, operational inefficiencies are controlled, and the risk of unexpected breakdowns is significantly reduced.

This approach is typically organised across weekly, monthly, quarterly, bi-annual and annual intervals, with each stage focusing on progressively deeper levels of inspection and servicing.

Weekly & Monthly Operational Checks: Routine operational inspections ensure baseline efficiency and flag developing faults before they trigger a system trip.

Quarterly Routine Maintenance: Quarterly servicing focuses on minor component cleaning and electrical safety verifications.

Annual Comprehensive Overhaul: Annual servicing should be timed ahead of peak summer cooling loads to maximize reliability when the system is under the highest stress.

By implementing a structured schedule, building operators can maintain stable system performance, reduce wear on critical compressor components, and ensure ongoing compliance with design intent and energy efficiency targets.

The following key maintenance tasks should be undertaken in accordance with the defined service intervals to ensure reliable compressor operation, optimise system efficiency, and minimise the risk of unexpected failure.

• Clean Heat Exchangers: Inspect and clean condenser and evaporator tubes to remove fouling, ensuring efficient heat transfer and preventing increased energy consumption or reduced system capacity.

• Check Refrigerant Charge and Pressures: Verify refrigerant charge levels and operating pressures are within design parameters to maintain efficiency and prevent compressor stress or damage.

• Inspect Compressor Lubrication: Check compressor oil level and condition, and undertake oil analysis or replacement where required to ensure effective lubrication and reduce wear on internal components.

• Log System Operating Data: Record suction and discharge pressures, operating temperatures (chilled water entering/leaving and condenser water entering/leaving), and compressor motor current draw to monitor performance trends and identify abnormalities.

• Inspect Compressor Operation: Observe compressor start/stop cycles, vibration levels and operating noise to detect early signs of mechanical wear, imbalance or control instability.

• Test Controls and Sensors: Verify calibration and operation of temperature sensors, pressure sensors and safety interlocks to ensure accurate system control and protection functions.

• Inspect Electrical Connections: Check and tighten electrical terminals, contactors and motor connections to prevent overheating, voltage drop or intermittent electrical faults.

• Verify Chilled Water Flow: Measure chilled water flow rates and differential pressure across the system to confirm hydraulic performance aligns with design requirements.

• Check Water Treatment Systems: For water-cooled systems, verify chemical treatment dosing and water quality to prevent scaling, corrosion and biological growth within pipework (legionella) and heat exchangers.

• Inspect for Refrigerant and Water Leaks: Visually inspect pipework, valves and joints for signs of leakage, including oil staining, corrosion or pressure loss, to prevent system inefficiency and environmental impact.

• Clean Strainers and Filters: Remove and clean all system strainers and filters to maintain unrestricted flow and prevent debris-related blockages or reduced heat exchange efficiency.

• Verify BMS Operation and Control Sequences: Confirm Building Management System integration, setpoints and control logic are operating correctly to maintain efficient and stable system performance.

• Test Safety Devices: Functionally test high and low pressure cut-outs, flow switches and freeze protection devices to ensure safe shutdown and protection of critical equipment.

• Inspect Insulation and Pipework Condition: Assess insulation integrity, pipework supports and system condition to identify deterioration that may lead to energy losses or long-term asset degradation.

What are the Applicable Regulatory Requirements

Chiller systems must be designed, installed, commissioned and maintained in accordance with jurisdiction-specific building codes, referenced mechanical services standards and recognised industry guidance. While the fundamental technical principles of refrigeration, heat transfer and system safety remain consistent globally, compliance frameworks vary between Australia, the United Kingdom and Canada in terms of statutory instruments, referenced guidance documents and accepted maintenance methodologies.

Australia

Chiller maintenance in Australia is legally bound to strict public health regulations and rigorous industrial codes to manage energy output and prevent biological risks.

• AIRAH DA19 (HVAC&R Maintenance): Published by the Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH), the DA19 Guide is the industry baseline for asset care. It dictates exact, frequency-based checklists (weekly up to annual overhauls) specifically engineered to optimize chiller thermodynamic efficiency and manage lifecycle performance.
• AS/NZS 3666 (Microbial Control): For water-cooled systems, compliance with AS/NZS 3666 (Parts 1, 2, and 3) is a mandatory legal requirement across all states. This standard mandates the strict cleaning, water-quality sampling, and chemical regulation of cooling towers and condenser loops to mitigate Legionella proliferation.
• The Ozone Protection and Synthetic Greenhouse Gas Management Act: This legislation legally binds mechanical contractors to monitor, log, and immediately remediate refrigerant leaks, requiring a certified ARCtick license for any intrusive refrigerant recovery or pressure testing.

United Kingdom:

Chiller maintenance in the UK focuses heavily on rigorous occupational safety, environmental F-Gas controls, and statutory energy efficiency benchmarks.

• SFG20 (The Definitive Standard for Building Maintenance): Managed by the Building Engineering Services Association (BESA), SFG20 provides the statutory, color-coded maintenance schedules used to govern chiller assets. It explicitly dictates critical “red” (legally mandatory) tasks, including electrical interlock safety testing, and “amber” (optimal function) tasks, like coil cleaning.
• BSRIA BG 50: The Building Services Research and Information Association (BSRIA) provides definitive rules for closed heating and cooling networks. BSRIA BG 50 details the rigorous water treatment protocols required for the chilled water closed loop to prevent system corrosion and internal fouling.
• CIBSE Guide M (Maintenance Engineering and Management): Issued by the Chartered Institution of Building Services Engineers, CIBSE Guide M dictates the operational guidelines for calculating asset degradation, economic life cycles, and standard testing frequencies for centralized plant items.
• UK F-Gas Regulations & TM44 Inspections: Depending on the total CO2 equivalent charge of the system, chillers must undergo mandatory, scheduled leak checks under F-Gas rules. Furthermore, under the Energy Performance of Buildings Regulations, any air conditioning system with an effective rated output above 12kW must undergo a statutory TM44 Energy Assessment every five years.

Canada:

Chiller operations in Canada balance federal environmental protection laws alongside provincial building safety codes and standardised industrial frameworks.

• CSA B52 (Mechanical Refrigeration Code): Developed by the Canadian Standards Association, CSA B52 is the core standard governing the design, construction, installation, and preventative maintenance of refrigeration systems. It sets strict regulatory boundaries for emergency relief valve testing, mechanical plant room ventilation operation, and compressor pressure safety controls.
• Federal Halocarbon Regulations (CEPA): Under the Canadian Environmental Protection Act, the Federal Halocarbon Regulations strictly mandate regular leak testing intervals, written equipment logs, and precise tracking of refrigerant recovery or top-ups for centralized chiller plant configurations.
• National Building Code of Canada (NBC) & Provincial Health Acts: Provincial health regulations (such as Quebec’s RBQ regulations for cooling towers) mandate automated chemical tracking, bi-weekly biocidal checks, and independent laboratory testing to shield open condenser water systems from microbiological hazards.

Conclusion: Why should I Maintain a Chiller?

Chiller performance is ultimately defined by the quality of ongoing maintenance, not just initial installation. As part of integrated building services systems, even small deviations in refrigerant charge, heat exchanger cleanliness, sensor accuracy or control sequences can have a significant impact on energy use, reliability and occupant comfort.

Effective chiller management therefore depends on a coordinated approach that combines planned preventative maintenance with accurate system monitoring, performance logging and robust compliance documentation. Maintaining clear service records, validating control strategies through the BMS, and ensuring all works align with applicable standards are essential to sustaining operational performance.

As building systems become more complex and efficiency-driven, structured maintenance and well-controlled technical documentation are critical to protecting asset value, ensuring compliance and maintaining long-term system efficiency.