What is the purpose of a lockout relay in a comfort cooling control circuit?

• A. An Automatic Restart Of The HVAC Equipment
• B. Overheating Condition Protection
• C. Reverse Cycle Prevention
• D. Short Circuit Protection

Answer: (A)

The lockout relay acts as a safety gate in the control circuit, preventing the compressor from starting when a fault or unsafe condition exists. When a fault occurs, the relay locks out the start circuit so the equipment cannot energize. Once the fault is cleared or the control resets, the relay releases and the system can start automatically in response to a cooling call. This automatic restart capability is what the relay is designed to provide, ensuring the equipment comes back on without manual intervention once it’s safe.

This isn’t primarily about protecting against overheating (that’s handled by thermal sensors and cutoffs), nor about preventing a heat pump from cycling into a reverse cycle, nor about protecting against a short circuit (that's handled by fuses or breakers). The lockout relay’s main role is to gate starts and allow automatic restart when conditions return to safe.