After changing a transformer, what must be done before energizing the customer?

• A. Repaint the transformer
• B. Install a resettable breaker
• C. Wait for 30 minutes
• D. Check for proper voltage

Answer: (D)

After replacing a transformer, the essential step before energizing the customer is to verify the voltage on the load side. A transformer can be wired for the wrong tap or have a misconnection, and without checking the secondary voltage you might feed the customer something outside the rated level, which can damage equipment or create safety hazards. By using a calibrated voltmeter to measure the output and confirming it matches the expected service voltage within tolerance, you ensure the transformer is wired correctly and delivering the correct voltage.

Cosmetic tasks like repainting don’t affect electrical safety or performance. Adding a resettable breaker isn’t a required step just to energize after replacement, since protection devices should already be properly configured in the system. Waiting a set time isn’t a standard requirement for energizing once the installation is complete. The practical, safety-focused check is to confirm proper voltage before turning the service back on.