When should my central plant chiller be maintained? The answer to this relatively simple question is a bit more nuanced than many would suppose. The commonly cited industry standard is that chiller maintenance should be completed during the winter, so any identified faults can be corrected while the machinery is shutdown and there is no cooling load. However, this approach is limited, as operational or static faults cannot be readily detected. Without a cooling load, during cold months running malfunctions such as seal leak or a poorly adjusted expansion valve cannot be remediated.
Central plant chillers represent a large capital investment as part of the overall building profile. When functioning properly, they can provide reliable energy efficient cooling for many years. When properly maintained and tuned, chillers can provide better cooling value per KW than many other distributed cooling solutions. With that energy efficiency potential, comes several pitfalls where a chiller out of calibration can cost building owners time and money in repairs and wasted energy use.
A chiller maintenance plan should be tailored to fit each building’s situation. It depends on many factors including chiller type, redundancy, criticality of load, operational goals, equipment age and location. For example, an air-cooled chiller located on the roof of a single-story building, adjacent to an open field may need to be cleaned more than once a year due to pollen clogging the condenser coils. A water-cooled chiller with a ground level cooling tower may need to have a greater frequency of tube brushing due to excess sediment build-up in the condenser fluid.
As a general rule of thumb, a minimum of four maintenance visits per year should be made to a chiller. The first can be fall shutdown, where a final operational and conditional assessment of the chiller is made. Major repairs resulting from the fall visit, as well as winter teardown work, where tasks that take significant time such as tube cleaning can occur. Spring start-up and testing would then be the third visit in a normal maintenance cycle, where the chiller is prepared to run for the summer. At the spring visit, any repairs made over the winter can be tested to ensure proper functionality with a full load test. Finally, a fourth visit should take place during the summer to ensure smooth operation under the continual heavy load demands of the season.
Proper chiller maintenance can extend the life of this critical piece of building equipment. Chiller overhauls arising from a lack of proper maintenance can be costly and time consuming. However, the risk of such events can be mitigated through consistent routine maintenance.