What testing should be performed before re-energizing a B28 system after maintenance?

• A. Leak checks
• B. Detector calibration verification
• C. Electrical equipment integrity
• D. Leak checks, detector calibration verification, electrical equipment integrity, and a safe re-commissioning procedure

Answer: (D)

Before re-energizing a B28 system after maintenance, you need to re-commission it with a complete safety check that covers leaks, detectors, electrical health, and the restart process. Flammable refrigerants create ignition risk, so first you verify there are no leaks that could allow buildup. Detectors must be calibrated and verified so they will respond at the correct level if a hazardous atmosphere develops, ensuring timely alarms. Electrical equipment integrity is vital to prevent faults, shorts, or sparks during restart that could ignite leaks or damage components. Finally, following a safe re-commissioning procedure ensures the restart is performed in a controlled, documented way, with proper sequencing, safeguards, and monitoring. Taken together, these checks address the main hazards and provide a confident, safe return to service; doing only part of them could miss a leak, a miscalibrated detector, a faulty connection, or an unsafe restart condition.