Codes, Regulations, and Safety Practices
What you must understand
Code questions reward precise recall of structure rather than memorized numbers. In the NEC, Article 690 governs photovoltaic systems, Article 705 covers interconnection, Article 250 grounding, Article 300 wiring methods, and Article 480 storage batteries. Rapid shutdown requirements, labeling, disconnects, ground-fault protection, and arc-fault protection are frequently tested. Local amendments, the authority having jurisdiction, and the utility interconnection process can all be stricter than the base code.
Safety content blends electrical and fall protection. Expect DC arc hazards, shock hazard from an array that cannot be switched off at the source, lockout/tagout, PPE, ladder and roof-edge work, and heat stress. Battery work adds off-gassing, arc flash, and chemical hazards.
Traps that appear in questions
- Confusing the rapid-shutdown boundary limits inside versus outside the array boundary.
- Assuming the national code overrides local amendments - the stricter rule applies.
- Isolating AC only and treating the DC side as dead.
- Skipping fall protection for a "quick" roof check.
Worked example
Rapid shutdown: within the array boundary, conductors must be reduced to a safe limit - commonly ≤30 V - within 30 seconds of shutdown; outside the boundary, the limits differ and are tighter on energy. Memorize the principle first: the goal is to make conductors safe for firefighters, and both voltage and energy limits apply. Then attach the exact numbers your code edition and AHJ require.