What does NEC® require for protecting cabling run across floor joists in an attic?

The National Electrical Code (NEC) mandates that when cabling is installed across floor joists in an attic, it must be protected from physical damage. This is particularly important in spaces like attics where there may be foot traffic, equipment placements, or other activities that could lead to inadvertent damage of the wiring.

Substantial guard strips serve as a physical barrier, ensuring that the cables are shielded from potential impacts or abrasions that could occur. By requiring these protective measures, the NEC aims to enhance the safety and longevity of the electrical installation. The use of guard strips indicates a proactive approach to preventing electrical hazards that could arise from wear and tear over time.

In contrast, the other options do not provide adequate protection for the cabling. Exposed installations may lead to increased risk of damage, nonmetallic sheathed cables alone do not address the potential for physical impact, and manually installed protective coverings can be less effective if not done consistently. Thus, opting for substantial guard strips aligns with NEC guidelines to ensure safety and code compliance.