Proper maintenance on chiller and condensing units is critical to efficient, trouble free operation. When combining the fact that most chillers and condensing units are situated in low traffic locations and out of sight (i.e., behind buildings, hidden behind walls, on rooftops, etc.,) with the fact that the coil cleaning portion of the maintenance process is an unpleasant and time consuming task. However, chiller and condensing unit maintenance isn't one of those jobs that most technicians look forward to. In situations where the maintenance department is busy or understaffed, coil cleaning is likely to be deferred beyond the time when maintenance is actually required by the equipment.
Unless you monitor the chiller kW draw with an energy management system or with a separate metering device, you will most likely learn about the problem when it's hot and you are unable to maintain chilled water and/or environmental temperatures, when you see your energy consumption skyrocketing, or when your compressor fails.