- The National Electrical Code (NEC) requires a grounding electrode conductor to be connected to a metal water piping system within a specific distance from the entry point.
- According to NEC Section 250.68(C)(1), this connection must occur within the first 5 feet (1.52 m).
- The correct option is 5 feet.
- Final Answer: \(\boxed{c}\)
Explanation
- Analysis of the NEC Grounding Requirement
The problem asks for the maximum distance from the point where a metal water pipe enters a building that a grounding electrode conductor must be connected to it, according to the National Electrical Code (NEC). This is a standard safety regulation intended to ensure proper grounding and bonding of the electrical system to the water piping. Understanding these standards is critical for electrical safety and compliance with building codes.
- Identifying the Mandatory Code Distance
According to the National Electrical Code (NEC), specifically section 250.68(C)(1), when the metal water pipe is used as a grounding electrode or part of a grounding electrode system, the connection of the grounding electrode conductor must be made within the first 5 feet (1.52 m) from the point where the metal water piping system enters the building. Any portion of the pipe that is further than this distance is not considered suitable for the connection of the grounding electrode conductor, primarily due to the potential for the piping to be modified (such as by replacing sections with non-metallic materials) which would interrupt the grounding path.
- Conclusion and Final Selection
Comparing the code requirement of 5 feet (1.52 m) with the provided options:
A25 ft (7.5 m)
B10 ft (3.0 m)
C5 ft (1.52 m)
The correct distance is 5 feet, which corresponds to option c. Therefore, the grounding electrode conductor must be connected at some point within the first 5 feet (1.52 m) of where the water pipe enters the building. The final answer is \(\boxed{c}\).
Examples
In residential or commercial electrical installations, ensuring that the grounding system is properly bonded to the metal water piping is essential for safety. For instance, when an electrician is installing a main service entrance for a building, they must adhere to the 5-foot rule to guarantee that the path to the ground remains continuous and reliable, even if repairs are made to the plumbing system later. This standard is frequently checked during building inspections to ensure the safety of the occupants and the protection of the electrical equipment.