Chiller Winter Maintenance

Preparing Your Chillers for Winter: A Technical Guide for UK Facilities

As temperatures drop and winter approaches, many UK manufacturers, processors, and commercial facilities shift their focus to heating and insulation. However, overlooking your chillers during this seasonal transition can result in operational issues, energy inefficiencies, and costly repairs. Whether your chillers operate year-round or are due to be temporarily decommissioned, winter preparation is essential for protecting system integrity, maximising efficiency, and ensuring a smooth return to full performance in spring. Here at Newsome, we support our clients with both rental and capital chiller systems, offering servicing and chiller maintenance to ensure long-term resilience. We’ll explore how to prepare your chillers for winter – from glycol levels and condenser protection to control system checks and water quality management.

1. Understand Your Chiller’s Operational Role in Winter

Not all chillers are shut down during winter. Some facilities – such as those in food processing, pharmaceuticals, or plastic manufacturing – may run chillers year-round to maintain critical process temperatures. Others may rely on them seasonally and store them over winter.

Before creating a winter plan, determine whether your chiller will:

• Continue operating under reduced demand
• Be partially shut down but kept ready for backup
• Be fully decommissioned for the winter period

Each scenario requires a different approach to maintenance and protection.

2. Review Glycol Concentration for Freeze Protection

As ambient temperatures begin to fall, one of the most critical tasks in preparing chillers for winter is to ensure that your cooling medium is adequately protected against freezing. For most water-based systems, this involves checking and adjusting the glycol concentration. Inadequate freeze protection can cause water in pipework, heat exchangers, or evaporators to solidify and expand, leading to burst pipes, internal damage, and extensive system downtime. In the UK, a 30% propylene glycol to 70% water mix is typically sufficient for protection down to approximately -12°C, but colder or more exposed locations may require stronger concentrations. Regular testing with a refractometer will confirm your current glycol level, and any top-up should use the same glycol type already present in the system. For food processing or pharmaceutical environments, propylene glycol must meet food-grade standards, and system components must be verified for material compatibility. Thorough mixing and circulation of the fluid are essential after any adjustment to ensure consistent protection throughout the network.

3. Insulate External Pipework and Vulnerable Components

During winter, exposed pipework and system components are at greater risk of freezing, particularly in rooftop installations or unheated plant rooms. Proper insulation is vital to preserving thermal efficiency and protecting the system from freeze damage. Closed-cell foam insulation with a durable vapour barrier is recommended to prevent both conductive heat loss and condensation formation, which can degrade the insulation over time. Components such as condensate lines, flow and return pipes, buffer tanks, sensors, and valves should all be assessed for exposure. In especially vulnerable areas, electric trace heating can be installed as a safeguard, automatically activating in sub-zero temperatures to prevent standing water from freezing. It’s also important to inspect and repair any degraded or weathered insulation before winter arrives. Leaving even small gaps uninsulated can result in localised freezing and compromise the system’s ability to maintain safe operating conditions.

4. Check Control Systems and Winter Modes

Modern chiller control systems are often equipped with winter operation features designed to maintain reliability and efficiency during colder months. These might include reduced condenser fan speeds, intelligent compressor staging, or anti-frost routines that activate system heaters in low-temperature conditions. Before winter, engineers should verify that all sensors are functioning accurately and that firmware or software settings are correctly programmed to reflect expected ambient conditions. Setpoints should be reviewed and adjusted if needed, ensuring the unit responds correctly to falling temperatures. Where chillers are integrated into larger site-wide BMS or SCADA systems, synchronising control logic across all platforms is essential to avoid false alarms or control conflicts. A winter readiness check should also include tests of alarms, fault notifications, and redundancy features, as early detection of anomalies becomes especially important during periods of low or fluctuating demand.

5. Monitor Flow Rates and Bypass Circuits

As production output typically fluctuates during winter, so too does the thermal load on the chiller system. This can lead to lower water flow rates, especially in systems that modulate in response to demand. However, many chillers have a minimum required flow rate to prevent freezing at the evaporator coil and to maintain stable refrigerant pressures. Where system load is reduced, flow rates can drop below this threshold, increasing the risk of poor performance or freeze-related faults. To counter this, bypass circuits or buffer tanks may be necessary to ensure continuous circulation. In systems without automatic flow control, operators should closely monitor differential pressures and inspect any flow sensors or variable-speed pump settings. Periodic cleaning of strainers, filters, and pump impellers is also essential to prevent partial blockages that could restrict flow and contribute to localised freezing within the system.

6. Clean Condensers and Prepare for Cold Ambient Air

Winter conditions can present both advantages and challenges for air-cooled condensers. While lower ambient temperatures typically improve the efficiency of heat rejection, they can also lead to excessive pressure drops within the refrigeration circuit if condenser airflow is not controlled effectively. In preparation for winter, condenser coils should be thoroughly cleaned to remove dirt, debris, and plant matter, all of which can obstruct airflow and create cold spots that worsen in frosty conditions. Fan motors and bearings should be checked to ensure consistent operation, and any variable-speed controls should be tested for correct response at low ambient temperatures. Where applicable, pressure-regulated condenser fans should be tuned to prevent short-cycling or excessive noise during light load conditions. Systems not designed for low ambient operation may require modifications, such as head pressure control valves or condenser fan cycling to maintain safe discharge pressures during winter.

7. Drain and Decommission if Out of Use

For chillers that are not required during the colder months, a full decommissioning process is the safest approach. Simply switching the unit off without draining it can leave residual water in pipes, valves, or coils, which may freeze and expand when temperatures drop below zero. A proper decommission includes draining the entire system, blowing through any pipework with compressed air to eliminate trapped water, and disconnecting power at the isolator. All fluid connections should be capped or sealed to prevent dirt ingress or pest contamination. Chillers stored outdoors may need temporary weather covers, while those in indoor locations should still be protected from accidental activation. Lockout-tagout procedures are strongly advised to prevent unauthorised use. When spring returns, the recommissioning process should include a full inspection, cleaning, leak checks, and recommissioning of control systems before the unit is brought back into operation.

8. Plan Ahead with Preventive Maintenance

Winter is often a quieter period for many facilities, making it an ideal time to carry out essential preventive maintenance. Even if the chiller is still in use, lower system loads allow for more accessible servicing windows and a reduced risk of disruption. Key tasks include inspecting the refrigeration circuit for leaks or irregular pressure readings, testing electrical panels and control logic, and cleaning filters, evaporators, and pump strainers. Performance logs from the previous months can be reviewed to spot trends or early warning signs of wear. Where relevant, software updates and recalibration of sensors can also be performed. A robust winter maintenance schedule not only helps prevent emergency breakdowns but also extends the working life of critical equipment and ensures consistent performance when higher loads return in spring.

9. Keep an Emergency Response Plan Ready

No winter preparation plan is complete without a robust contingency strategy. Unexpected events such as power failures, pipe bursts, or extreme cold snaps can take even well-maintained systems offline. For businesses reliant on temperature-sensitive processes, unplanned chiller failure can result in product loss, downtime, and safety hazards. An emergency response plan should include details of critical spares, approved service contractors, and procedures for contacting technical support. Having a relationship with a trusted rental provider such as Newsome allows for rapid mobilisation of emergency chiller hire, with units ready for dispatch nationwide. Whether it’s a short-term hire for contingency coverage or a long-term supplementary unit to support ageing infrastructure, having a plan in place ensures continuity of operations when the unexpected happens.

Conclusion

Winter preparation isn’t just about preventing frozen pipework – it’s about keeping your operations efficient, safe, and compliant. Whether your chillers are running continuously, operating under reduced load, or being temporarily decommissioned, careful planning can prevent costly disruptions and preserve system performance. At Newsome, we provide capital and rental chiller systems backed by full installation, maintenance, and chiller repair services. Our nationwide team is here to help you prepare your plant for winter – and get the most from your cooling investment year-round.

Need help winterising your chiller systems?

Call us on 01422 371 711 and contact our team to schedule a winter service or emergency hire assessment.

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