Which of the following connections is allowed on the supply side of the service disconnecting means?

The permissible connections on the supply side of the service disconnecting means are limited to devices that protect the electrical system or enhance its reliability and safety. Surge arresters are designed specifically to protect electrical equipment from voltage spikes, typically caused by lightning strikes or other transient events. Since they are protective devices, their installation is allowed on the supply side of the service disconnect, where they can effectively mitigate the risk of damage before the electrical service reaches other parts of the electrical system.

In contrast, standard lighting circuits and residential AC units are typically connected on the load side of the service disconnect. This placement complies with the NEC’s requirement for safety and organization in residential and commercial wiring systems. Similarly, sub-panels, which distribute power to different areas or circuits, are also connected on the load side. These systems are meant to operate under the jurisdiction of the main disconnect and require proper protection, which is not applicable on the supply side. Thus, the connection of surge arresters on the supply side aligns with the NEC guidelines for optimal protection and functionality.