🔍 Key Concepts

• Trace the control (dashed) lines from the compressor safety devices (high-pressure, low oil pressure, etc.) to see which valve coil is affected by a safety shutdown. • Identify which valve is in the refrigerant line that should stay open during normal low-pressure cut-out cycling, so suction and discharge can equalize without trapping liquid. • Look for the valve whose symbol shows an energized-to-open solenoid that is wired so it only de‑energizes (and thus closes) when a safety device opens the circuit, not during normal thermostat/low‑pressure cycling.

💭 Think About

• On this diagram, when the low-pressure cut-out stops the compressor in normal operation, which valve(s) would still need to stay open so the system can equalize and restart smoothly? • Which numbered valve has its solenoid coil controlled directly by the safety shutdown circuit rather than by the thermostat or low-pressure control used for normal cycling? • Compare the valves located near the compressor suction and liquid line: which one would you expect to close only if the compressor must be protected from damage, not just turned off for temperature control?.

✅ Before You Answer

• Verify which numbered valve symbol is connected (by dashed control lines) in series with all safety switches such as high-pressure cut-out and oil failure switch. • Confirm that this same valve is not controlled by the normal cycling device (room thermostat / evaporator pressure / low-pressure control). • Double-check the location in the piping: the correct valve will be in a line where closing it on a safety trip will protect the compressor, but leaving it open during normal off-cycles will not harm the system.