Which of the following circuits is not allowed to be grounded in a Class III location?

In the context of grounding in a Class III location, healthcare facilities have specific requirements that prioritize patient safety and the reliability of medical equipment. In these environments, certain circuits are designed to ensure that no ground fault can occur, reducing the risk of electrical shock or failure of critical medical devices. Grounding these circuits could introduce the possibility of electrical interference or fault scenarios that might compromise patient safety.

In contrast, options that involve electric cranes, secondary lighting circuits, and Class 2 load side circuits for power grid systems are designed and utilized in a manner where grounding may be necessary or beneficial for operational safety and reliability, making them appropriate for grounding in various contexts.

Therefore, the circuits in healthcare facilities are distinct in their need to avoid grounding to maintain the integrity of the electrical system and protect patients and equipment.