Lockout relays in air conditioning systems are used to prevent what?

• A. Prevent compressor short-cycling
• B. Lock out the overloads
• C. Lock out the thermostat
• D. Provide automatic restart

Answer: (A)

Lockout relays are designed to prevent compressor short-cycling. When a fault is detected or power is interrupted, the relay locks the compressor from restarting for a set period or until the fault is cleared. This prevents the compressor from repeatedly starting and stopping, which can cause excessive wear, overheating, and inefficient operation. They’re not meant to lock out the overloads, they don’t lock out the thermostat, and they don’t provide automatic restart—quite the opposite: they suppress restart until the issue is resolved.