Which action is a typical function of the high pressure switch when pressures are high?

Which action is a typical function of the high pressure switch when pressures are high?

• A. Continue operation despite high pressure
• B. Turn off compressor if high pressures exceed 350-400 psi
• C. Calibrate evaporator temperature
• D. Turn on low-pressure switch

Answer: (B)

High pressure protection. The high pressure switch serves as a safety control that shuts the compressor off when the refrigerant high-side pressure reaches a set limit. If conditions cause the high-side pressure to spike—such as blocked airflow across the condenser, an overcharge, or very high ambient temperatures—the switch opens the electrical circuit to the compressor (or its contactor), preventing damage from overpressure. The typical cut-off range for many systems is around 350–400 psi, though the exact value depends on the refrigerant and design. This safety function is distinct from protecting against low suction pressure (that’s the low-pressure switch) and is not used to adjust evaporator temperature. Allowing the compressor to continue running under high pressure can lead to component damage, so the automatic shutoff is the correct behavior.

High pressure protection. The high pressure switch serves as a safety control that shuts the compressor off when the refrigerant high-side pressure reaches a set limit. If conditions cause the high-side pressure to spike—such as blocked airflow across the condenser, an overcharge, or very high ambient temperatures—the switch opens the electrical circuit to the compressor (or its contactor), preventing damage from overpressure. The typical cut-off range for many systems is around 350–400 psi, though the exact value depends on the refrigerant and design. This safety function is distinct from protecting against low suction pressure (that’s the low-pressure switch) and is not used to adjust evaporator temperature. Allowing the compressor to continue running under high pressure can lead to component damage, so the automatic shutoff is the correct behavior.