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Cooling Maintenance

Chiller Maintenance Checklist

A maintenance checklist and schedule for air-cooled, water-cooled, and process chillers — covering compressor checks, condenser maintenance, refrigerant management, F-Gas compliance, and efficiency monitoring for commercial and industrial cooling systems.

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What is a chiller maintenance checklist?

A chiller maintenance checklist is a structured list of the 18 preventive maintenance tasks — covering visual, functional, cleaning, safety and record-keeping checks — that keep a chiller running safely and reliably. It groups routine checks by frequency, from daily inspections to annual servicing, so FM teams and building engineers can plan and evidence preventive maintenance.

Core chiller checks

  • Inspect for refrigerant leaks
  • Check chilled water supply and return temperatures against design ΔT
  • Clean air-cooled condenser coils with appropriate fin-friendly coil cleaner
  • Test all safety controls: HP/LP cutouts, flow switches, freeze stat and oil safety
  • Update the asset's F-Gas logbook with charge, top-up, leak test and engineer's cert

Which type of chiller do you have?

The checks below apply to every chiller. Each type also has its own checklist covering what is specific to it.

Air-cooled chiller maintenance checklist

Condenser coil cleaning and fin condition, ambient derating, head pressure control and fan/VSD checks.

Water-cooled chiller maintenance checklist

Condenser tube fouling and approach temperature, eddy current testing, water treatment and ACoP L8 duties.

Process chiller maintenance checklist

Glycol condition, reservoir and filtration, temperature tolerance and N+1 redundancy under continuous duty.

Chiller maintenance schedule

Frequency-led: daily and weekly logs through to the annual shutdown, with F-Gas leak-check intervals.

What is a chiller?

A chiller produces chilled water for air conditioning, process cooling, or data centre cooling. It works by evaporating refrigerant to absorb heat from the chilled water loop, then rejecting that heat via an air-cooled or water-cooled condenser. Chillers are among the highest energy-consuming assets in a commercial building, making planned maintenance essential for both reliability and efficiency.

Air-cooled chillers reject heat directly to ambient air via fin-and-tube condenser coils and fans. They are self-contained, require no cooling tower or condenser water circuit, and are commonly installed on rooftops or in plant rooms. Well-suited to small and medium commercial buildings, they are simpler to commission and maintain than water-cooled alternatives.

Water-cooled chillers reject heat to a cooling tower via a condenser water loop, delivering better efficiency at full load. They are the typical choice for larger commercial buildings and data centres where capacity and running cost matter. They require more infrastructure — cooling tower, condenser water pump, and water treatment — but deliver lower energy costs over time. Process chillers serve industrial, pharmaceutical, and manufacturing applications with tighter temperature tolerances and often continuous operation requirements, making a structured planned chiller maintenance schedule especially critical.

This checklist is one of 34 in our HVAC maintenance checklists, covering air handling units, fan coils, chillers, VRF, ductwork and extract systems — filters, coils, refrigerant and damper checks.

Typical Chiller maintenance checklist

A practical starting point for planned preventive maintenance. Always refer to the manufacturer's O&M manual and site-specific requirements.

Chiller maintenance checklist showing tasks such as log operating parameters (pressures, temps and check for leaks and oil staining, each with its service frequency
A preview of the Chiller maintenance checklist — the full 18-task routine, service frequencies and safety notes are below, free to download as a PDF.

Visual Checks

  • Inspect for refrigerant leaks — check joints, schrader caps, oil staining and brazed connections
  • Inspect water-cooled condenser tubes for fouling, scaling and tube end erosion
  • Check compressor oil level, colour and acidity (TAN) — log against trend
  • Inspect starter panel, contactors, terminations and check star/delta or VSD operation
  • Check anti-vibration mounts, pipework supports and refrigerant pipe insulation
  • Inspect evaporator and condenser for tube fretting or vibration damage (water-cooled)

Functional Checks

  • Check chilled water supply and return temperatures against design ΔT
  • Verify condenser water temperatures (water-cooled) or ambient conditions (air-cooled)
  • Record refrigerant suction and discharge pressures
  • Calculate and verify superheat and subcool against manufacturer target range
  • Check compressor operating current against full load amps (FLA) on each phase
  • Verify chilled water flow rate against design and confirm CHW pump operation
  • Review BMS trending data — flag drift in pressures, currents, ΔT and run hours
  • Check expansion valve operation (TEV/EEV) and superheat stability

Cleaning & Housekeeping

  • Clean air-cooled condenser coils with appropriate fin-friendly coil cleaner

Safety Checks

  • Test all safety controls: HP/LP cutouts, flow switches, freeze stat and oil safety

Record Keeping

  • Update the asset's F-Gas logbook with charge, top-up, leak test and engineer's cert
  • Record kW input vs cooling load and calculate kW/ton or COP for the visit

Download the free Chiller maintenance checklist PDF

Get all 18 tasks as a printable PDF — free, no signup needed. Keep a copy in the plant room, attach it to work orders, or share it with your maintenance contractor.

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Typical maintenance frequency

Suggested intervals for chiller maintenance. Actual frequencies should follow manufacturer guidance and site-specific risk assessments.

Monthly

  • •Log operating parameters (pressures, temps, currents)
  • •Check for leaks and oil staining
  • •Clean air-cooled condenser coils where dust loading is high

Quarterly

  • •Full operating check under design load
  • •Test safety controls and freeze protection
  • •Oil analysis on large chillers (>250 kW)

Every 6 Months

  • •F-Gas leak check on systems ≥50 tonnes CO₂e
  • •Inspect VSD or starter for harmonics/insulation issues
  • •Review chilled water quality and inhibitor levels

Annually

  • •Comprehensive chiller service
  • •F-Gas leak check and logbook update (5–50 t CO₂e systems)
  • •Eddy current test of condenser tubes (water-cooled)
  • •Compressor oil and filter change
  • •Electrical thermography of panel and motor terminations

Common faults and issues

Issues to be aware of when maintaining chiller equipment.

Condenser fouling — dust on air-cooled fins or scale/biofilm in water-cooled tubes reducing heat rejection and lifting head pressure
Refrigerant charge loss — small leaks at schrader cores, sight glasses, or relief valve seats degrade efficiency long before they trigger a fault
Compressor bearing or motor winding failure on older units — often preceded by rising motor current or oil acidity
Low chilled water flow causing evaporator freeze protection trips — usually a clogged strainer, failed CHW pump, or closed valve
Control sensor drift on suction/discharge pressure transducers or CHW temperature sensors causing inefficient operation or short cycling
Expansion valve hunting — unstable superheat causing the compressor to cycle on LP or run wet
VSD harmonic distortion or insulation breakdown causing nuisance trips on chillers retrofitted with inverter drives
Crankcase heater failure on shut-down chillers leading to liquid slugging on next start — common after extended winter shutdowns
Loose or oxidised electrical terminations causing voltage imbalance, motor overheating and premature winding failure
Water treatment failure on condenser circuit allowing scale, corrosion or biofilm that destroys efficiency and shortens tube life

Safety and compliance notes

Key safety considerations for chiller maintenance. This is general guidance only — always follow OEM instructions, statutory requirements, and your organisation's safe systems of work.

Chillers contain large refrigerant charges — all refrigerant work must be done by F-Gas certified engineers under EU/UK F-Gas regulations
Large chillers operate at high voltages (400V+) and high currents — observe electrical safe working practices, lock-off and prove-dead procedures
Test high and low pressure safety cutouts at least annually — they protect the compressor from catastrophic failure
Water-cooled chillers must be treated for legionella risk as part of the cooling water management plan (HSE ACoP L8)
When checking refrigerant pressures, use rated gauges and minimise opening the system — every disconnect risks a small loss and contamination
Liquid refrigerant causes severe cryogenic burns — wear face shield and gauntlets when working at service valves

Reference standards and frameworks

United Kingdom
SFG20, CIBSE Guide M, and the UK F-Gas Regulations for refrigerant plant
North America
ASHRAE/ACCA Standard 180, plus EPA Section 608 refrigerant handling rules

Frameworks commonly referenced when planning chiller maintenance programmes. Always confirm the requirements that apply to your site and jurisdiction.

How PM Assist helps

Managing Chiller documentation with PM Assist

PM Assist helps FM and building operations teams search their O&M manuals and building drawings in seconds. Upload your chiller documentation and ask questions like “What is the rated cooling capacity?” or “When was the last F-Gas leak check?” — and get source-cited answers instantly.

See PM Assist answer questions about a real chiller manual — try the live demo, no signup needed.

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Further reading on chiller maintenance

Reactive vs Planned Maintenance Explained·Why Building Engineers Waste Hours Searching Documentation·How AI Can Transform Facilities Management·All articles

Compliance topics for chiller maintenance

F-Gas Regulations Explained·SFG20 Explained: The Standard for Building Maintenance·Planned Preventive Maintenance (PPM) Explained·TM44 Air Conditioning Inspections Explained·All topics

Related guides

Find Equipment Specifications Across Building Documents·Find Maintenance Schedules in O&M Manuals·Search Building System & Maintenance Records with AI·Planned Preventive Maintenance Documentation·All guides·UK facilities management statistics

Frequently asked questions

What does process chiller maintenance involve?
Process chiller maintenance covers the same core refrigerant circuit tasks as comfort cooling chillers — compressor oil analysis, refrigerant pressure and superheat checks, F-Gas leak testing, and electrical thermography — but with tighter tolerances and typically a more frequent schedule. Process chillers often run 24/7 and serve manufacturing, pharmaceutical, or data centre loads where temperature stability is critical. Key differences: evaporator and condenser water quality is usually more tightly controlled (often DI or deionised water loops); setpoint accuracy is more critical (±0.5°C vs ±2°C for comfort cooling); and shutdown windows for maintenance are narrower. A structured planned process chiller maintenance schedule with monthly parameter logging, quarterly safety control tests, and annual compressor oil and F-Gas compliance work is the minimum baseline for a continuously-operated process chiller.
What is the difference between an air-cooled and water-cooled chiller?
An air-cooled chiller rejects heat to the ambient air via condenser coils and fans, while a water-cooled chiller rejects heat to a cooling tower via a condenser water circuit. Water-cooled chillers are generally more efficient at full load (typically 0.5–0.7 kW/ton vs 1.0–1.3 kW/ton for air-cooled) but require a cooling tower and associated water treatment. Air-cooled chillers are simpler to install and maintain, with no cooling tower or water hygiene regime to manage.
How do I know if my chiller is losing efficiency?
Monitor kW/ton or COP regularly. Compare operating pressures and temperatures to the original commissioning data. Rising condenser pressure, falling suction pressure, or increasing compressor current for the same cooling load all indicate declining performance. BMS trending is invaluable — set up dashboards for ΔT across evaporator and condenser, compressor current per cooling kW, and approach temperatures. Anything more than ~10% drift from commissioning values warrants investigation.
How often do chillers need F-Gas leak checks?
Under UK/EU F-Gas regulations, frequency depends on CO₂-equivalent charge. Systems with 5–50 tonnes CO₂e need annual checks; 50–500 tonnes need 6-monthly checks; 500+ tonnes need quarterly checks. Permanent leak detection halves the required frequency. Your chiller's data plate shows the refrigerant type and charge weight, which you multiply by the refrigerant's GWP to get tonnes CO₂e.
What does a chiller site visit or service call cover?
A reactive chiller site visit covers reading fault codes, checking operating pressures and temperatures against expected values, testing safety cutouts, inspecting for leaks, and identifying the root cause of any fault or trip. A planned service follows a structured checklist covering refrigerant circuit, electrical systems, condenser, evaporator, and compressor — plus the F-Gas logbook update and a formal handover report so the FM team can evidence statutory compliance.
How often should a water-cooled chiller be serviced?
Water-cooled chillers require monthly parameter logging, quarterly full-load performance inspection and safety control tests, and an annual comprehensive service. The annual service should include condenser tube eddy current testing to detect wall thinning, compressor oil analysis, electrical thermography, and full F-Gas documentation. Cooling tower maintenance must be coordinated as part of the same regime — condenser water quality directly affects chiller performance and tube condition.
What should a planned chiller maintenance schedule include?
A planned chiller maintenance schedule (PPM) typically includes: monthly operating parameter logs (suction and discharge pressures, chilled water in/out temperatures, compressor currents); quarterly full-load inspection and safety control tests; semi-annual F-Gas leak checks on systems above the regulatory threshold; and a comprehensive annual service covering compressor oil change, condenser cleaning, electrical thermography, and refrigerant circuit documentation. The schedule should be held in a CAFM or PPM management system and tracked against the site asset register.
How much does chiller maintenance cost per year in the UK?
For a typical mid-size commercial chiller (200–500 kW), annual PPM contract pricing in the UK ranges roughly from £1,500 to £4,500 depending on whether it's an air-cooled package or a water-cooled centrifugal unit, plus F-Gas obligations and access. Reactive call-outs are typically charged at £450–£800 per visit before parts. Refrigerant top-ups are increasingly expensive — R410A and R134a have risen substantially under the F-Gas phasedown, so leak avoidance is the single biggest cost-saving measure on older chillers.
What are the most common chiller fault codes?
Generic fault categories (which most manufacturers code differently) include: HP trip (high discharge pressure — usually condenser fouling or fan failure), LP trip (low suction pressure — refrigerant loss, low flow, or expansion valve issue), low oil pressure, freeze stat trip (low evaporator water temperature), flow switch fault (CHW pump or strainer issue), and motor overload (electrical fault, voltage imbalance, or mechanical seizure). Always cross-reference the manufacturer's O&M manual — codes differ between Daikin, Carrier, Trane, York, Mitsubishi, Climaveneta and others. The PM Assist chiller diagnostic tool gives a manufacturer-agnostic walk-through of these categories.
Should I repair or replace an old chiller?
Repair vs replacement depends on remaining useful life, refrigerant phase-out status (R22 systems are end-of-life; R410A and R134a are restricted under F-Gas phasedown), efficiency vs current standards, and the cost of the next major intervention (compressor rebuild, tube bundle replacement). As a rough rule, if the next major repair exceeds 50% of replacement cost and the unit is over 15 years old or uses a phasing-out refrigerant, replacement usually wins on lifecycle cost — especially given the energy savings of modern variable-speed inverter chillers.
How does BMS integration improve chiller maintenance?
A chiller integrated into the BMS allows continuous trending of suction/discharge pressures, ΔT across evaporator and condenser, compressor currents and run hours, and any fault flags. This shifts maintenance from reactive (waiting for a trip) to predictive (spotting drift). Set up BMS alarms on key parameters — e.g. discharge pressure above 90% of HP cutout, ΔT collapse, run hours indicating short-cycling — and the FM team gets a week or more of warning before a hard fault.
Why does my chiller short-cycle?
Short cycling — repeated start/stop within minutes — is usually caused by an oversized chiller running on a small load, low chilled water buffer volume, faulty thermostat or BMS control band, fouled evaporator (poor heat transfer triggers HP trip), or refrigerant charge issues. It rapidly destroys compressors. Diagnose by checking the cycle pattern against load profile and verifying setpoint deadband, buffer tank sizing (typically 5–10 litres per kW for variable load) and refrigerant pressures.
What is superheat and why does it matter on a chiller?
Superheat is the amount the refrigerant temperature exceeds its saturation temperature at suction pressure — typically 5–8°C target on most chillers. Too low (less than 3°C) risks liquid refrigerant entering the compressor and causing slugging damage. Too high (more than 12°C) means the evaporator isn't fully fed and capacity drops. Measuring superheat at every service is the fastest way to spot expansion valve issues, refrigerant undercharge, or evaporator fouling. The PM Assist chiller diagnostic tool calculates superheat from suction pressure and line temperature for the major refrigerants.

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