SERVICE & MAINTENANCE


Chillers that do more than chill


Today’s modern chillers are sophisticated, multifunction machines that can heat while they cool, and in some cases, do both independently too. Polyvalent heat pumps sit at the heart of this evolution, but with their fl exibility comes complexity. Tim Mitchell, Sales Director for Klima-Therm provides his maintenance top-tips for chillers that do more than chill.


"For polyvalent machines, coil cleanliness, water


treatment and controls calibration are particularly critical."


T


he biggest mistake we see is a polyvalent system being treated as though it were simply a slightly more advanced version of a standard chiller or heat pump - it is neither of these things. Polyvalent HVAC is part of a uniquely interdependent system, designed to do multiple jobs at a time, responding dynamically to building demands, in order to provide stand-alone cooling, stand-alone heating, and heat recovery, i.e. cooling and heating simultaneously. Polyvalent machines are four-pipe heat pump systems,


off ering simultaneous or stand-alone, independently controlled heating and cooling, making them particularly versatile and effi cient indoor temperature control devices. Not all four-pipe heat pumps are polyvalent, however - four-pipe systems also include chillers that recover heat, or heat pumps that can switch between heating and cooling modes, but not necessarily control both simultaneously.


In a polyvalent system, heating or cooling demand is


concurrently or independently combined with a cooling or heating requirement from the building, achieved by making use of energy that is otherwise rejected as part of the production of chilled or hot water. In contrast, a simple four-pipe heat pump system might comprise distinct fl ow and return pipes that work in heating mode and separate pipes that deliver cooling, with one


side being the byproduct of the other rather than being independently controllable.


Predictive maintenance As with all modern HVAC plant, predictive maintenance has an important role to play in extending the life and effi ciency of polyvalent chillers. Techniques such as vibration analysis, infrared thermography, ultrasonic testing and motor current analysis allow for the detection of early signs of mechanical or electrical issues before they develop into failures. For polyvalent machines, coil cleanliness, water treatment and controls calibration are particularly critical. With interfaces between three stand-alone heat exchangers (two refrigerant- to-water and one refrigerant-to-air), it is critical that the heat exchange is never compromised and that controls are regularly checked to ensure accuracy of readings and response. Oil and refrigerant analysis is another valuable predictive tool. Annual laboratory testing can detect moisture ingress, acid formation and metal contamination. These contaminants not only reduce effi ciency but can also cause longterm damage to compressors, valves and bearings if left unchecked. Predictive maintenance should be combined with an ongoing preventative maintenance strategy, ensuring the HVAC plant is regularly checked, focusing on a number of key areas. Over time, these routine tasks will create a picture that can lead to improved operations:


The importance of data and daily logging One of the simplest yet most powerful tools in preventative maintenance is the daily operating log. Recording temperatures, pressures, fl ow rates and energy consumption provides a snapshot of how the machine is behaving in real time. Comparing this data with design and commissioning benchmarks makes it much easier to identify abnormal conditions.


Up-to-date logs build a performance history that can be analysed to identify trends. Gradual effi ciency losses, rising condenser or reducing evaporator pressures or unstable operating modes can all be detected early, allowing corrective action to be taken before the situation becomes critical.


18 May 2026 • www.acr-news.com Download the ACR News app today


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