Final answer:
Moisture typically enters the refrigerant system of low-pressure chillers through leaks in seals or gaskets, especially when the system's pressure drops below atmospheric levels.
Step-by-step explanation:
On low-pressure chillers, moisture most frequently enters the refrigerant system through leaks that can occur whenever there is a breach in the system's seals or gaskets. These breaches can become pathways for moisture to ingress, especially during times when the system is under low pressure, and even more so if the chiller is turned off and the internal pressure drops below atmospheric pressure.
Preventive maintenance and regular checks of the system's integrity are critical to ensuring that such leakage is minimized, as moisture within a refrigerant system can lead to significant issues including a reduction in efficiency, formation of acids, and corrosion.