Chiller Maintenance: Common Issues, Solutions & Tips
Chillers are often the largest single energy user in a building or process cooling system, so small problems show up quickly as higher utility bills, warm spaces, or process upsets. This guide explains how chillers work, the main types, the most common chiller issues and how to fix them, the readings to log, and a chiller maintenance checklist by frequency.
How a Chiller Works
A chiller removes heat from water (or a water-glycol mix) and rejects it somewhere else. The chilled water then circulates through air handlers or process equipment to cool buildings, machines, or products.
Most chillers use the vapor-compression cycle. Refrigerant absorbs heat from the water in the evaporator, the compressor raises its pressure and temperature, the condenser rejects that heat to outside air or to condenser water from a cooling tower, and an expansion device drops the pressure so the cycle can repeat. Pumps move the chilled water and condenser water; the refrigerant stays sealed inside the chiller.
Chiller problems usually trace back to three causes: maintenance neglect, improper operation, and incorrect sizing. The sections below cover each, then the specific issues and fixes.
Types of Chillers
| Type | How It Rejects Heat or Works | Maintenance Notes |
|---|---|---|
| Air-cooled | Fans blow outdoor air across condenser coils | Keep coils clean; check fans and motors; common where water is limited or space is tight |
| Water-cooled | Condenser water carries heat to a cooling tower | Generally more efficient; needs condenser tube cleaning, water treatment, and cooling tower maintenance |
| Absorption | Uses a heat source (such as steam, hot water, or gas) and an absorbent solution instead of a mechanical compressor | Specialized service; solution and vacuum condition matter |
| Evaporative-cooled | Water evaporating over the condenser helps reject heat | Water quality, scale, and biological control are key |
Vapor-compression chillers are also described by their compressor type: scroll and reciprocating for smaller units, screw for mid-size, and centrifugal for the largest. Compressor type affects the maintenance schedule, oil service, and how the chiller handles low loads.
The Three Root Causes of Chiller Problems
1. Maintenance Neglect
Skipped inspections, dirty tubes and coils, and poor water treatment reduce capacity and raise energy use long before anything fails. Routine inspections, reading logs, and trend analysis tell you the chiller’s real condition so you can plan preventive and corrective maintenance.
2. Improper Operation
Chiller manuals spell out correct operating procedures, startup and shutdown sequences, and setpoints. Running outside them may not stop the chiller right away, but it makes costly failures more likely and shortens equipment life. Training operators and following written procedures prevents most of these problems.
3. Incorrect Sizing
An undersized chiller can’t keep up with the load. An oversized one runs at low load much of the time, which can cause short cycling and higher operating costs. If loads have changed since the chiller was installed, re-evaluate whether its capacity still fits.
Common Chiller Issues and Solutions
Even with good operation and maintenance, aging and wear cause problems. Knowing the common troubleshooting steps helps you narrow down the cause before a repair call.
| Issue | Likely Causes | What to Check or Do |
|---|---|---|
| Chiller won’t start | Power supply problem (loose wire, blown fuse, tripped breaker); control or sensor fault; safety lockout (low refrigerant pressure, low flow, high pressure); compressor or motor failure | Check power and the controller’s fault code first; confirm chilled and condenser water flow; reset only after the cause of any safety trip is found |
| Not enough cooling (leaving water too warm) | Low refrigerant charge or a leak; fouled condenser or evaporator tubes; dirty air-cooled condenser coils; failing compressor; load higher than the chiller’s capacity | Compare temperatures and pressures to the log; check approach temperatures; clean coils or tubes; leak-check the refrigerant circuit |
| High head (condenser) pressure | Fouled condenser tubes or coils; cooling tower or condenser water problem; low condenser water flow; non-condensable gases in the system | Clean the condenser; check cooling tower operation and condenser water flow and temperature |
| Low suction pressure or evaporator freezing | Low refrigerant charge; low chilled water flow; setpoint too low; fouled evaporator | Verify chilled water flow and flow switch; check charge and setpoints; freezing can damage tubes, so investigate immediately |
| Low or unstable water flow | Failed or undersized pump, clogged strainer, closed or partly closed valves, air in the piping | Check pumps and strainers, valve positions, and flow readings; bleed air from the loop |
| Frequent cycling or tripping | Oversized chiller at low load; incorrect setpoints or control settings; flow problems; electrical issues | Review load and control settings; check flow; have electrical supply and components checked |
| Unusual noise or vibration | Worn compressor bearings, loose mounts, pump cavitation, refrigerant flow problems | Check mounts and couplings; consider vibration analysis on compressors and pumps |
| Low liquid level alarm (process chillers) | Leaks in the circulation loop or evaporation from an open reservoir | Find and repair leaks; top up with the correct coolant mix |
Environmental and Load Changes
Sometimes the chiller is fine but the conditions changed: process changes add heat load, outdoor temperatures rise, nearby equipment adds heat around an air-cooled unit, pipe insulation is damaged or missing, or line voltage shifts. Check these before assuming the chiller itself has failed.
Common Chiller Faults and Alarms
Most modern chillers display a fault or alarm code when something affects performance. These codes are usually specific and speed up diagnosis, so always record them in the work order.
- Low temperature warning: the leaving water or process temperature dropped below the user setpoint. Often caused by a light heat load or an alarm set too high.
- High temperature warning: the temperature rose above the user limit, from a high heat load or an alarm set too low.
- Over-temperature safety: a temperature passed a safety cutoff set by the manufacturer or user, which may point to a refrigeration system problem.
- Low flow or flow switch trip: chilled or condenser water flow dropped too low, which protects the evaporator from freezing.
- High or low refrigerant pressure: safety trips that point to condenser, charge, or flow problems.
- Low liquid level: the reservoir in a process chiller is low from leaks or evaporation.
Chiller Readings to Log and What They Tell You
Chiller logs are the best early-warning system you have. The key is to track the same readings consistently and watch the trend, since what counts as normal varies by chiller and design.
| Reading | How to Calculate It | What a Rising Trend Can Mean |
|---|---|---|
| Chilled water delta T | Entering chilled water temp − Leaving chilled water temp | A shrinking delta T can point to flow or control problems |
| Condenser approach | Refrigerant condensing temp − Leaving condenser water temp | Fouled condenser tubes or non-condensable gases |
| Evaporator approach | Leaving chilled water temp − Refrigerant evaporating temp | Fouled evaporator tubes or low refrigerant charge |
| Efficiency (kW per ton) | Compressor power (kW) ÷ Cooling load (tons) | The chiller is using more energy for the same cooling |
For example: chilled water entering at 54°F and leaving at 44°F gives a delta T of 10°F. A chiller drawing 420 kW while producing 600 tons of cooling runs at 420 ÷ 600 = 0.70 kW per ton. If that number creeps up month over month at similar loads, something is costing you efficiency, often dirty tubes. Compare readings against the manufacturer’s design data and your own history.
Chiller Maintenance Checklist
These are general guidelines. Follow the manufacturer’s recommendations for your chiller type and model, and adjust for your load and water conditions.
| Frequency | Typical Tasks |
|---|---|
| Daily | Log temperatures, pressures, flows, and amps; review alarms and fault codes; check for leaks, unusual noise, or vibration |
| Weekly | Review log trends; check oil level and pressure where applicable; inspect strainers and pumps; check water treatment readings |
| Monthly | Inspect air-cooled condenser coils and fans; check electrical connections and starter; leak-check refrigerant circuit; verify flow switches and safety controls |
| Quarterly | Oil analysis on larger compressors; calibrate sensors and controls; review water treatment results with your provider |
| Annually | Clean condenser tubes (water-cooled) and inspect evaporator tubes; clean air-cooled coils thoroughly; change oil and filters as specified; test safety devices; full inspection by a qualified technician; eddy current tube testing periodically on larger chillers |
Water-cooled chillers depend on the cooling tower, so maintain both together. See the commercial HVAC maintenance checklist and CMMS for HVAC maintenance.
Safety and Compliance
- Refrigerant work: in the U.S., technicians who service refrigerant circuits must be certified under EPA Section 608, and larger systems have leak repair and recordkeeping requirements.
- Lockout/tagout: isolate electrical energy and relieve pressure before service. See what lockout/tagout is.
- Machinery rooms: keep refrigerant detectors, ventilation, and alarms working as required by code.
- Water treatment chemicals: follow safety data sheets and handling procedures.
How a CMMS Helps Manage Chiller Maintenance
A computerized maintenance management system (CMMS) organizes chiller maintenance and makes problems easier to spot.
Scheduled maintenance. Daily logs, monthly inspections, and annual tube cleaning are generated as work orders automatically, so they don’t get skipped.
Records and trends. Every job records the work done, parts and materials used, and test results, so you can spot recurring problems and support repair-or-replace decisions.
Alerts and follow-up. Work orders and notifications go to the right people when tasks come due or problems are found, so issues get fixed quickly.
Monitoring. eWorkOrders supports MQTT-based monitoring from pre-configured sensors or gateways, including temperature, alarms, and other equipment measurements such as pressure. The available documentation does not identify specific sensor brands or building automation systems; contact eWorkOrders support to confirm compatibility with a particular device or system.
Frequently Asked Questions
What are the most common chiller problems?
Common chiller problems include failure to start, inadequate cooling, high head pressure, low suction pressure or evaporator freezing, low water flow, frequent cycling, and unusual noise or vibration. Most trace back to maintenance neglect, improper operation, or incorrect sizing.
How often should a chiller be serviced?
Chillers need daily reading logs, weekly and monthly inspections, quarterly checks such as oil analysis on larger units, and annual service including tube cleaning on water-cooled chillers. Follow the manufacturer’s recommendations for your model.
Why is my chiller not cooling enough?
Common causes are low refrigerant charge, fouled condenser or evaporator tubes, dirty air-cooled condenser coils, a failing compressor, low water flow, or a heat load higher than the chiller’s capacity. Comparing current readings against the chiller log usually narrows it down.
What is condenser approach temperature?
Condenser approach is the difference between the refrigerant condensing temperature and the leaving condenser water temperature. A rising approach over time often means the condenser tubes are fouled and need cleaning.
What is the difference between air-cooled and water-cooled chillers?
Air-cooled chillers reject heat to outdoor air using fans and condenser coils. Water-cooled chillers reject heat to condenser water, which a cooling tower then cools. Water-cooled chillers are generally more efficient but need cooling tower and water treatment maintenance.
What does chiller maintenance include?
Chiller maintenance includes logging temperatures and pressures, checking for leaks, cleaning condenser and evaporator tubes or coils, maintaining water treatment, oil analysis and changes, testing safety controls, calibrating sensors, and inspecting electrical components.
Conclusion
Chillers reward consistent care. Log the same readings every day, watch the trends, keep tubes, coils, and water clean, and follow the manufacturer’s operating procedures. As a result, you catch most problems early, keep energy costs down, and extend the chiller’s life.
Keep Every Chiller Log and Inspection on Track
Chiller problems show up in the readings long before they show up as a failure, but only if logs and inspections happen on schedule. That’s what preventive maintenance software is for. eWorkOrders has supported maintenance operations for over 30 years, serving teams at Honda and King River Packaging, rated 4.9 on Capterra and G2.
About the author: Janet Jaquis is Marketing Director at eWorkOrders, where she writes about maintenance strategy, asset reliability, and CMMS software for maintenance and facility teams.
