If the stack sensor has been triggered on a refrigeration plant, what is the most likely cause?

The most likely cause of a triggered stack sensor in a refrigeration plant is that the pressure relief valve has opened. A stack sensor is typically used to monitor conditions related to pressure within the refrigeration system. When pressure levels exceed safe operating limits, the safety mechanism, which includes the pressure relief valve, activates. This opening of the valve allows excess pressure to escape, thereby protecting the system from potential damage due to overpressure.

In contrast, while a clogged or dirty filter can impact the overall efficiency of the system, it would not directly cause the stack sensor to trigger. Similarly, a malfunctioning compressor could lead to various operational issues, but it may not necessarily lead to the triggering of the stack sensor unless it resulted in a condition severe enough to affect pressure. Lastly, while sensor calibration is important for accurate readings, a need for calibration would not cause the sensor itself to trigger; it simply means that the readings may not be reliable. Thus, the triggering of the stack sensor is most closely associated with the action of the pressure relief valve to ensure safety within the refrigeration system.