What is a chiller, and how does it work?
A chiller is a central cooling machine that chills water for a building or a production process. The chilled water (typically 7 °C) flows through pipes to fan coil units, air handling units or process machines, absorbs heat and returns at about 12 °C. The chiller rejects this heat outdoors through a refrigeration cycle consisting of a compressor, condenser, expansion valve and evaporator.
Large buildings such as hospitals, shopping malls, office towers, data centers, factories and public buildings use chillers instead of split air conditioners, because they deliver controlled cooling to hundreds of points from a single central plant.
Chiller types
| Type | How it rejects heat | Where it is used | What to watch for |
|---|---|---|---|
| Air-cooled | To outdoor air via condenser fans | Rooftop and ground-level installations, buildings where a cooling tower is not feasible | Fouled condenser fins trigger high-pressure alarms in summer |
| Water-cooled | With condenser water and a cooling tower | Large-capacity facilities, plant rooms | Cooling tower water chemistry and scaling in shell-and-tube condensers |
| Scroll compressor | Several small compressors operate in stages | Small and medium capacities | When one compressor fails, capacity drops but the unit keeps running |
| Screw compressor | Screw rotors, slide valve capacity control | Medium and large capacities | Oil separator, oil filter and bearing life should be monitored regularly |
| Centrifugal | High-speed impeller | Very large central plants | Bearings and control system require specialist maintenance |
| Process chiller | Low temperatures with glycol water | Plastics, food, pharmaceutical and chemical production | Glycol concentration and freeze protection settings |
Our repair scope
Before replacing a unit, we tell you in writing whether it can be repaired. The quote shows the cost difference between overhaul and replacement as separate line items.
- Screw compressor overhaul: bearings, rotors, capacity slide valve, gaskets
- Scroll and reciprocating compressor replacement and recommissioning
- Winding insulation (megger) test and motor faults
- Oil analysis, oil separator and oil filter replacement
- Condenser fin washing, fan motor and fan blade replacement
- Descaling of shell-and-tube condensers and evaporators
- Chemical cleaning of plate heat exchangers and freeze damage repair
- Expansion valve (TXV / EEV) adjustment and replacement
- Control board, display, sensor and transducer replacement
- Leak detection, brazing, vacuum and refrigerant charging
- Water pump, flow switch and strainer service
- Soft starter, contactor and phase protection faults
Common alarms and possible causes
If you tell us the alarm on the display over the phone, the team knows in advance which part to bring. Repeatedly resetting the alarm can damage the compressor.
| Alarm | Common causes | What we do on site |
|---|---|---|
| High pressure | Dirty condenser, fan not running, insufficient cooling tower water, refrigerant overcharge | Condenser cleaning, fan and tower check, charge measurement |
| Low pressure | Refrigerant leak, clogged filter drier, expansion valve failure, low water flow | Leak test, drier replacement, valve adjustment, flow measurement |
| Freeze protection | Low water flow, faulty sensor, low setpoint, insufficient glycol | Flow and sensor check, setpoint, glycol measurement |
| Flow switch | Pump failure, clogged strainer, air in the system | Pump test, filter cleaning, air venting |
| Compressor thermal overload | Phase imbalance, winding failure, mechanical seizure | Current and megger measurement, phase check, overhaul decision |
| Low oil | Oil leaks, oil return problems, clogged oil filter | Oil level, filter and separator check, oil analysis |
| High discharge temperature | Low refrigerant, high superheat, valve failure | Superheat measurement, charge top-up, valve service |
Chiller maintenance schedule
The schedule below forms the basis of our annual maintenance contracts. For facilities with high operating hours, we increase visit frequency.
| Frequency | Work performed |
|---|---|
| Every day | Pressure, temperature and alarm logs kept by facility staff (we provide the form template) |
| Once a month | Condenser visual check, alarm history, compressor currents, water inlet-outlet temperatures |
| Every 3 months | Terminal tightness, contactors, sensor verification, leak check |
| Pre-season | Condenser washing, fan and bearing check, commissioning tests, safety device tests |
| Once a year | Oil analysis, megger test, heat exchanger cleaning, superheat and subcooling adjustment, efficiency report |
| Before winter | Glycol concentration or draining, freeze protection, preparation for long shutdowns |
Annual maintenance contract for your chillers
The schedule above, written measurement reports and priority breakdown response, all in one contract.
Chiller brands we service
We work on Carrier, York, Trane, Daikin, McQuay, Clivet, Rhoss, Ciat, Climaveneta, Lennox, Mitsubishi, LG, Midea, Gree, Üntes, Alarko and Aldağ chillers, and on all screw and scroll compressors, including Bitzer and Refcomp.
A4 form with checklist, measurement table and signature fields.Download PDFView the form
Looking for scheduled maintenance? See our chiller maintenance page for maintenance intervals, the checklist, the maintenance form and the factors that determine the price.
FAQ
How long does chiller maintenance take?
Scheduled maintenance of a single medium-capacity chiller usually takes between half a day and one day. Condenser washing and heat exchanger cleaning add time. We give the exact duration during the site survey.
Is cooling interrupted during maintenance?
If there are multiple chillers, we service them one at a time to keep cooling running. In facilities with a single chiller, we schedule maintenance outside working hours or during low-load periods.
How long do spare parts take to arrive for a compressor failure?
We keep commonly used sensors, valves, contactors and filters in stock. For compressors and brand-specific control boards, we state the supply time in writing in the quote; critical facility contracts include a stock plan for these parts.
Is it better to replace an old chiller or repair it?
We look at the unit's age, the refrigerant it uses and its energy consumption. We present repair and replacement options side by side, including the annual energy difference.