EPA Section 608 Universal Certification ExamCoreMedium
A technician is working on a low-pressure chiller operating with R-123. Which of the following is a common issue with these systems due to their operating pressures?
- AAir and moisture infiltration into the system due to operating below atmospheric pressure.
- BExcessive superheat causing compressor damage.
- CRefrigerant leaks are difficult to detect due to positive pressure.
- DHigh discharge pressures leading to compressor overheating.
Show answer & explanationAnswer & explanation
Correct answer: A. Air and moisture infiltration into the system due to operating below atmospheric pressure.
Low-pressure chillers, like those using R-123, often operate at pressures below atmospheric pressure. This creates a risk of non-condensable gases, primarily air and moisture, being drawn into the system through leaks, which can lead to corrosion, acid formation, and reduced efficiency.
Why the other options are wrong
- B. Excessive superheat can be an issue in any system, but it's not uniquely or primarily caused by the low operating pressures of R-123 chillers.
- C. Leaks are actually easier to detect externally on low-pressure systems because the system operates below atmospheric pressure, drawing air IN rather than pushing refrigerant OUT, but this also means refrigerant escapes when the system is shut down and pressure equalizes.
- D. Low-pressure chillers typically have low discharge pressures; high discharge pressure is characteristic of high-pressure systems.
Low-Pressure Chiller Challenges
Low-pressure chillers, such as those using R-123, operate at pressures below atmospheric, leading to unique challenges like air and moisture infiltration.
- Operate below atmospheric pressure (vacuum).
- Prone to air and moisture ingress through leaks.
- Requires purge units to remove non-condensables.
- Leaks can be hard to detect (inward leak vs outward refrigerant leak).
Memory trick: Low pressure, less than atmosphere, air and water sneak in there.