🔍 Key Concepts
• Relationship between low pressure refrigerants and operation slightly below atmospheric pressure
• Purpose of a high pressure cut-out switch on low pressure systems (to protect the chiller shell from overpressure)
• Difference between cut-out settings and relief valve settings (cut-out should act before a relief lifts)
💭 Think About
• What is the approximate maximum safe operating pressure for a low pressure chiller shell before you risk lifting a safety relief valve?
• Should the high pressure cut-out setting be lower than, equal to, or higher than the relief valve setting? How does that affect which answer choice you pick?
• Looking at 1, 5, 10, and 15 psig, which value best matches a point that is near the upper design/relief range for low pressure equipment, rather than normal operating pressure?
✅ Before You Answer
• Verify the typical design/relief pressure limit for low pressure refrigerant chillers (often around the low‑teens psig range).
• Confirm that a high pressure cut-out is a control/safety switch, not the ultimate relief device, so it should trip before a relief valve lifts.
• Compare each option (1, 5, 10, 15 psig) to what you know about normal vacuum/low positive pressures in these systems and eliminate any that are clearly too low to be a high-pressure safety cutoff.