The work of Chiller maintenance is the set of periodic inspection, cleaning and technical adjustment activities carried out to keep the performance of the water-cooled chiller at its optimal design operating level. Operating experience shows that a system not serviced on the correct cycle can consume an extra 20 to 30% electricity each month, while shortening equipment life from 15 to 20 years down to only 7 to 10 years.
Procedure Chiller maintenance to the Tan Long standard covers 6 groups of in-depth tasks: overall system inspection, servicing the refrigeration compressor, cleaning the condensing equipment, servicing the evaporating equipment, checking the refrigerant and lubricating oil systems, and finally a test run and acceptance. At the standard frequency of once every 3 months, or an overhaul after every 6,000 operating hours, scheduled maintenance costs range from only 5 to 15 million VND depending on capacity — far lower than
This article analyses each technical item in detail, identifies 5 early warning signs that need immediate attention, and explains how to set a maintenance schedule suited to your cold storage system and production plant.
What is a chiller? Why does scheduled chiller maintenance matter?
Chiller water chiller is the central piece of equipment, the “heart” of an industrial refrigeration system. Its job is to chill water down to 5 to 12 degrees C (41 to 53.6 degrees F) to supply the industrial refrigeration such as FCUs, AHUs, specialist heat exchangers, or to serve a food production line directly. Industrial chiller capacities typically range from 20 refrigeration tons (70 kW) to more than 1,000 refrigeration tons (3,517 kW).
A chiller system operates on a closed vapour-compression cycle. In it, the refrigerant (commonly R134a, R410A, R407C or NH3) absorbs heat in the evaporator, then is raised to high pressure by the refrigeration compressor before rejecting heat in the condenser. Over a period of continuous operation, scale layers gradually form on the surface
Besides the scale problem, neglecting Chiller maintenance also leads to other serious consequences. The lubricating oil in the compressor oxidises, mechanical seals wear and lose their tightness, and moisture can enter the system and acidify the refrigerant. When these negative factors compound, they directly damage the compressor — the most expensive part of the entire system, with a very high replacement cost, usually Chiller maintenance carried out methodically is the best way to protect the capital investment and keep a company's production stable.
5 warning signs that a chiller system needs maintenance immediately
Recognising abnormal signs early is the best way for a business to save on operating costs. Below are 5 common symptoms together with their technical causes and the remedies delivered through professional Chiller maintenance :
1. Leaving chilled water temperature not meeting the design requirement
When the leaving chilled water temperature is 2 to 3 degrees C (3.6 to 5.4 degrees F) above the setpoint, that is the first sign that the heat exchanger is fouled with scale or that the refrigerant charge is low. During Chiller maintenance, the technician needs to measure the “approach temperature” (the temperature difference between the leaving water and the condensing refrigerant) to pinpoint the cause. If this figure has risen more than 2 degrees C above the original commissioning value, the condenser needs chemical cleaning immediately.
2. Chiller reporting a high pressure (HP) or low pressure (LP) fault
A high pressure fault usually appears when the condenser is fouled, a condenser fan has failed, or the chiller cooling tower is blocked. Conversely, a low pressure fault usually indicates a refrigerant leak or a blocked oil filter. Both fault types are logged and displayed on the PLC control cabinet, and they trip the protection relay, causing an emergency shutdown and interrupting production.
3. Abnormal increase in electricity consumption
If the ammeter on the control panel shows an operating current 10 to 15% above the manufacturer's rated current, the system is running inefficiently. Common causes include scale build-up in the condenser, insufficient lubricating oil for the refrigeration compressor or throttle valve stuck in the wrong position, forcing the machine to work harder to maintain capacity.
4. Abnormal vibration and noise from the compressor
Knocking, squealing or vibration above the 2.5 mm/s threshold (per ISO 10816) on the compressor body warns that the bearings are worn or the foundation bolts have loosened. If inspection and Chiller maintenance are skipped at this point, the damage progresses to a broken piston or a seized crankshaft, forcing the business to spend a very large sum on a full compressor overhaul.
5. Chilled water flow unstable or noticeably reduced
Chilled water flow more than 20% below the design level (measured with a flow meter in m3/h) usually stems from a failed water pump, a blocked strainer, or heavy scale build-up in the pipework. Low flow reduces the heat transfer coefficient in the evaporator, drives suction pressure down and can easily lead to freezing that cracks the evaporator industrial cold storage.
The technical chiller maintenance procedure at Tan Long
Procedure Chiller maintenance in full comprises 6 groups of tasks carried out in a strict sequence. Each stage has specific check parameters for the technician to record directly in the maintenance report, making it easy for the owner to track equipment condition.
Overall inspection and initial assessment
Before any intervention begins, the technician reads and records all current operating parameters of the industrial refrigeration system. The key data include suction pressure, discharge pressure, entering and leaving water temperatures at the condenser, entering and leaving water temperatures at the evaporator, compressor operating current, and any fault codes shown on the controller. This data is the essential reference for comparison once the Chiller maintenance is complete.
Next, the technician uses visual inspection to find oil leaks, cooling water leaks and corrosion on the housing, and to check the integrity of the thermal insulation on the chilled water pipework.
Refrigeration compressor maintenance
The compressor is the equipment group that directly determines the efficiency of the whole system. Servicing the refrigeration compressor includes checking the lubricating oil level through the sight glass and taking an oil sample to analyse acid content and moisture if the machine has run continuously for more than 6 months. At the same time, the technician uses specialist instruments to measure vibration and per-phase current in order to compare
For compressors running 8 hours a day, we recommend an oil change every 12 months. For systems operating 24/7 (three continuous shifts), the oil change should be carried out every 6 months. The lubricating oil must be exactly the type specified by the manufacturer — for example POE (Polyol Ester) oil for machines using R134a or R410A, and mineral oil for machines using R22. After every 6,000 operating hours,
Cleaning the condensing equipment (condenser)
On water-cooled chillers, shell-and-tube condensers usually accumulate calcium carbonate scale and mineral salts inside the copper tubes. Depending on the degree of blockage, the technician will use a mechanical tube cleaner or a chemical circulation pump
On air-cooled chillers, the outdoor condenser coil usually accumulates dust and insect debris on the aluminium fins. The technician uses a compressed air blower at 4 to 6 bar (58 to 87 psi) to blow against the airflow direction. If the aluminium fins are oxidised or bent, we use a specialist comb straightener to straighten them and restore the air flow area
Servicing the evaporating equipment (evaporator)
The evaporator in a water-cooled chiller system is also of shell-and-tube design. Although the scaling risk is lower because the water supply is usually treated, the technician still needs to clean the inlet strainer every quarter.
The biggest risk here is localised freezing when water flow is too low or the temperature setpoint is incompatible with the glycol concentration. During Chiller maintenance, the technician checks the tube surface temperature and compares it with the refrigerant saturation temperature. If suction superheat is below 3 degrees C (37.4 degrees F), the expansion valve needs to be readjusted immediately to
Checking the refrigerant and oil systems
A refrigerant leak not only reduces efficiency but also damages the environment. Tan Long uses an electronic detector to scan every weld, valve and pipe joint. In particular, on systems using NH3 (ammonia) — common in cold storage — we require litmus paper or an electrochemical probe for leak detection to guarantee absolute safety.
The refrigerant charge in the system must match the mass in kg specified on the nameplate. A shortfall of just 10% can reduce cooling capacity by 8 to 12%. The technician calculates liquid subcooling and superheat to assess the charge level accurately, rather than relying on a standard pressure gauge alone.
Test run and acceptance
After the technical items are complete, the system is restarted and monitored for at least 30 minutes. The acceptance criteria include chilled water temperature reaching setpoint within a tolerance of only 0.5 degrees C, compressor operating current not exceeding 95% of rated, stable pressures, and compressor vibration below
All parameters before and after Chiller maintenance together with the list of replaced parts are recorded clearly in the handover report. This is an important archive document that helps the business track operating history and optimise future repair costs through a modern PLC control panel system.
Standard chiller maintenance frequency
The chiller maintenance schedule is divided into 3 levels based on the depth of intervention and the cycle:
| Cycle | Main content | Duration |
|---|---|---|
| Monthly | Overall visual inspection, reading operating parameters, cleaning water filters, checking oil level | 2–4 hours |
| Quarterly (3 months) | All monthly items + cleaning the condenser, checking the refrigerant, checking compressor vibration, checking the electrics | 4–8 hours |
| Annually (overhaul) | All quarterly items + dismantling and inspecting the compressor valves, changing the oil, checking bearings and mechanical seals, chemically cleaning the condenser and evaporator | 1–3 days |
The quarterly inspection is the most important cycle, recommended by both ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and TCVN (Vietnamese Standards) for industrial chillers operating 8 hours a day or more.
For chillers running 24/7 in high ambient temperatures (above 35°C/95°F), as in southern Vietnam, the frequency should increase to once every 2 months to keep scaling and wear rates under control.
Optimising chiller maintenance cost based on system scale and capacity
Operating experience shows that the cost of Chiller maintenance is not fixed but calculated flexibly on three core factors: the machine's cooling capacity (in refrigeration tons), the equipment type (air-cooled or water-cooled), and the depth of technical intervention (a quarterly periodic inspection or a full annual overhaul).
At Tan Long, we build optimal Chiller maintenance packages for each specific capacity group to deliver the best economics for the business:
- Small-capacity systems: From 20 to 50 refrigeration tons (70 to 175 kW).
- Mid-range systems: From 50 to 150 refrigeration tons (175 to 527 kW).
- Large-capacity systems: From 150 to 500 refrigeration tons (527 to 1,758 kW).
- Very large machine sets: Above 500 refrigeration tons (more than 1,758 kW).
A basic service quotation normally excludes unplanned replacement parts such as valves, bearings or seals, additional refrigerant charging, and the specialist chemicals used to descale the condenser. All of these items are listed in detail by Tan Long technicians in the cold storage design plan or the site survey report, so the customer knows them before work begins.
Comparing the budget for scheduled Chiller maintenance against the cost of fixing a breakdown reveals a very large economic gap. Replacing a refrigeration compressor unit after serious damage can cost hundreds of millions of VND, not counting the enormous loss from 2 to 5 days of production line downtime. By contrast, the annual overhaul cost represents only a very small fraction of that
Telling water-cooled and air-cooled chiller maintenance apart
The two chiller types common in Vietnamese industry have different servicing requirements, particularly in the heat rejection section:
| Category | Water-cooled chiller | Air-cooled chiller |
|---|---|---|
| Heat rejection assembly | Cooling tower | Outdoor condenser |
| Regular cleaning | Flushing pipework, descaling the condenser, cleaning the cooling tower | Blowing dust off the condenser, straightening aluminium fins |
| Water treatment | Mandatory control of pH 7.0–8.5, hardness, Legionella bacteria | Not required |
| Specific risks | Scaling, microbiologically induced corrosion, Legionella | Dust blockage, high ambient temperature |
| Performance under Vietnamese conditions | Higher COP because the cooling water is cooler than the air | Lower COP when ambient temperature is > 35°C |
At food and seafood plants, water-cooled chillers dominate because their higher COP saves electricity in continuous operation. However, this type requires an additional water treatment system and monthly checks of circulating water quality.
Mandatory safety precautions when carrying out chiller maintenance
The work of Chiller maintenance is a technical procedure demanding absolute precision and strict adherence to the contractor's protective rules. Because this is a system operating at high pressure with complex mechanical and electrical equipment, neglecting safety factors can lead to serious risks to people and property. To ensure stable operation of the industrial refrigeration system, the engineering team at Tan Long always applies
- Electrical and mechanical safety: The technician must isolate the main power supply and carry out the lockout-tagout (LOTO) procedure on the PLC control panel before dismantling any mechanical component.
- Handling hazardous refrigerants: On machines using NH3 (ammonia) refrigerant, commonly fitted in industrial cold storage, personnel must wear a specialist respirator and chemical-resistant gloves, and always work in pairs when handling the refrigerant pipework.
- Pressure fire and explosion prevention: Never use an open flame or any equipment capable of producing an electrical spark in a machine room using R22 or R134a refrigerant. These are compressed gases carrying a very high pressure explosion risk if exposed to uncontrolled heat during Chiller maintenance.
- Control of specialist chemicals: Acids used to clean scale must be citric acid or formic acid, diluted to the correct technical concentration of 5 to 10%. Note in particular that hydrochloric acid (HCl) must not be used, because its extremely strong corrosiveness damages the copper tube surface and causes permanent harm to the heat exchanger of the water-cooled chiller.
Strict compliance with the technical safety instructions above not only protects human life but is also the key factor in extending equipment lifespan. At Tan Long, every inspection and fault-handling procedure is closely supervised to eliminate technical errors, so businesses can optimise production performance over the long term with confidence.
Why should businesses choose an experienced chiller maintenance provider?
System water-cooled chiller is an asset of very high investment value, typically ranging from several hundred million to several billion VND depending on production scale. Entrusting the equipment to technicians without the necessary expertise can cause serious secondary damage during Chiller maintenance as follows:
- Compressor overload: Charging refrigerant above the specified quantity directly creates excess pressure and overloads the refrigeration compressor.
- Lubricating oil precipitation: Using the wrong oil type or mixing incompatible oils leads to chemical precipitation, blocking filters and pipework.
- Liquid slugging faults: Operating the stop valves out of the correct technical sequence can easily cause liquid slugging, one of the leading causes of destruction to compressor pistons and crankshafts.
With a foundation of more than 20 years of experience in cold storage design and industrial refrigeration operation in Vietnam, Tan Long is proud to be the strategic partner of many large-scale seafood and food plants. Our engineers not only understand equipment construction in depth but are also equipped with specialist measuring instruments including refrigerant analysers and digital vibration meters
On every Chiller maintenancevisit, Tan Long commits to providing a detailed technical report with complete, accurate measurements taken before and after servicing. This data is an important basis for customers to track performance degradation trends closely, so they can plan component replacement proactively and optimise the operation of their industrial cold storage system. Contact Tan Long now for in-depth advice on the Chiller maintenance schedule best suited to the current condition of your equipment.
Frequently asked questions about chiller maintenance
How long does chiller maintenance take?
Quarterly scheduled maintenance for a mid-size chiller (50–150 refrigeration tons / 175–527 kW) usually takes 4–8 working hours. An annual overhaul with compressor dismantling and full chemical cleaning can run to 1–3 working days.
Can a chiller be serviced without shutting it down?
Some inspection items can be carried out while the machine is running (on-line inspection): reading operating parameters, measuring current, visual leak checks. However, cleaning the condenser, changing the oil and inspecting the compressor valves all require the machine to be shut down (off-line maintenance).
How often does a chiller need recharging with refrigerant?
A chiller operating normally in a sealed system does not need additional refrigerant. If pressure drops, the cause is a leak, and it must be found and repaired before topping up. Charging without repairing the leak is a temporary fix and a waste.
What is the difference between chiller maintenance and servicing?
In Vietnamese technical practice, these two terms are often used interchangeably. Strictly distinguished: maintenance is the set of actions preventing failure, including cleaning, lubrication and adjustment; upkeep is the broader concept, covering both preventive maintenance and restorative repair.
Frequently asked questions about chiller maintenance
Why does a chiller need scheduled maintenance?
Because the chiller is usually the largest electricity consumer in a facility. A fouled condenser or scaled water lines raise condensing pressure, driving electricity consumption up and compressor lifespan down.
Which signs show a chiller needs urgent maintenance?
Abnormally high electricity consumption under the same load conditions, chilled water failing to reach temperature, discharge pressure above the design value, the machine reporting faults and stopping repeatedly, or abnormal noise and vibration.
What does the chiller maintenance procedure cover?
Cleaning the condenser and water lines, checking the refrigerant charge and lubricating oil, checking current and motor insulation, calibrating sensors, checking protection devices and re-tightening electrical connections.
How does maintenance differ between water-cooled and air-cooled chillers?
Water-cooled chillers additionally need water treatment, cooling tower cleaning and condenser descaling. Air-cooled chillers focus on cleaning the heat exchange coil and checking the fans.
How often should a chiller be serviced?
The frequency depends on operating hours, the installation environment and the manufacturer's recommendations. The maintenance provider will set a specific schedule after surveying the actual system.
Does Tan Long provide chiller maintenance?
Yes. Tan Long provides scheduled maintenance and fault resolution for chiller systems in commercial buildings and factories.
Related pages
- What is glycol? Composition, types and applications in refrigeration systems
- Water chiller schematic diagram: details and technical standards
- What is a chiller? Structure and operating principle of the chiller system
- Industrial water chillers: Reliable installation quotes 2026
- water chiller
Is your business in need of a survey, upgrade, or new design for your industrial refrigeration system?
With over 18 years of practical experience leading more than 29 major national projects, Tan Long's team of HVAC engineers is committed to providing accurate thermal load calculations, optimizing the COP efficiency coefficient, switching between natural refrigerants NH3/CO2, and saving 20–30% in operating electricity costs.
Engineer Nguyen Toan Thinh (Technical Director)
With over 18 years of practical experience in directing, consulting, designing, and constructing heavy industrial refrigeration systems, ASRS automated warehouses, and IQF freezing systems across more than 29 major national projects.
