When a control transformer is used, what does NEC require regarding the secondary connections?

In the context of NEC requirements for control transformers, it is essential to ensure safety and reduce the risk of electrical shock. The National Electrical Code (NEC) mandates that one side of the secondary winding of a control transformer must be connected to ground. This requirement helps to establish a reference point for the control circuit and promotes safe operation.

By connecting one side to ground, any potential hazardous voltage that might occur on the secondary side of the transformer can be minimized, providing a pathway for fault currents. This grounding practice helps to protect the equipment and personnel from electrical hazards, ensuring that the control system operates safely.

Grounding both sides of the transformer secondary, as indicated in the chosen answer, reinforces the overall safety by ensuring that any fault scenarios have a direct and effective grounding path. However, the exact NEC code specifics can depend on the application and local regulations, which is why relying on just the first option might lead to confusion without understanding the underlying reasons for grounding in electrical control systems.

Considering the safety implications and NEC guidelines, it becomes clear that grounding is a critical aspect when using control transformers, which supports the selection of the answer.