Plan Review, Inspection Simulation, and Article 705/706 Interconnection

Why Plan Review and Inspection Matter

Every residential PV system must pass two code checkpoints before it can be energized: a plan review by the Authority Having Jurisdiction (AHJ) before permits are issued, and a field inspection after installation is complete. Both checkpoints use the National Electrical Code (NEC), primarily Article 690 for PV systems and Article 705 for interactive (grid-tied) systems. As an installer, understanding what reviewers look for lets you submit clean permit packages, pass inspections on the first visit, and avoid costly rework.

Reading a Residential Permit Package

A typical residential PV permit package includes a site plan, a one-line electrical diagram, a load calculation, and equipment cut sheets. When you review these documents the way an AHJ does, you are checking that every element on paper matches code requirements before anyone picks up a tool.

Common plan-review deficiencies include:

• Conductor sizing errors — the wire gauge shown on the one-line must handle the continuous current (125 percent of Isc per NEC 690.8) and any temperature or conduit-fill correction factors.
• Missing or incorrect labels — Article 690 requires specific warning labels at the DC disconnect, the inverter, the service panel, and wherever conductors from more than one power source could be present.
• Rapid shutdown coverage — NEC 690.12 requires rapid shutdown of PV system conductors on or in buildings; the one-line must show the listed rapid-shutdown device or compliant inverter and indicate the boundary.
• GFPD notation — ground-fault protection is required; the one-line must show the device and its rating.
• Missing equipment specifications — cut sheets must confirm that every listed component is appropriate for its rated voltage and current.
• Grounding and bonding details — module frames, racking, and equipment grounding conductors must be sized and shown per 690.43 and 690.45.

When you mark a deficiency, follow the AHJ format: circle or cloud the error on the drawing, write the NEC section number violated, and state the required correction in plain language.

Conducting a Field Inspection

A field inspection is a physical walk-through of the completed installation. Use a standardized checklist and move systematically: start at the array, follow the DC conductors to the combiner box or inverter, then continue to the AC disconnect and service entrance.

Safety first during any inspection walk-through. Wear your PPE — hard hat, safety glasses, and gloves — at all times on or near the roof mock-up. Treat all conductors as energized. Never bypass lockout/tagout procedures: if an instructor or lead asks you to trace a live circuit, confirm LOTO status before touching anything. Remember that PV modules generate voltage whenever light hits them; there is no way to de-energize the array by flipping a breaker alone.

Key items on an inspection checklist:

| Category | What to Verify |

|---|---|

| Voltage markings | DC voltage of the system posted at the DC disconnect and service panel per 690.53 and 690.54 |

| Conductor protection | Conduit type appropriate for location; no exposed conductors where required to be protected |

| Grounding | EGC continuity through racking; grounding electrode conductor size and connection |

| Disconnects | Accessible, labeled, correct interrupting rating |

| Rapid shutdown | Device installed and labeled; boundary marked |

| GFPD | Listed device present and rated correctly |

| Labeling | All required NEC 690 warning labels present and legible |

Article 705: Interactive System Interconnection

Article 705 governs the connection of power production equipment — including PV inverters — to the electric utility grid. The two most commonly tested provisions are the 120-percent rule and the distinction between supply-side and load-side connections.

The 120-Percent Rule (NEC 705.12)

When a PV inverter feeds power back into a panelboard through a back-fed breaker, the total of (1) the panel's main breaker rating plus (2) the inverter back-fed breaker rating cannot exceed 120 percent of the busbar rating.

> Formula: Inverter breaker ≤ (Busbar rating × 1.20) − Main breaker rating

For example, a 200 A busbar allows a maximum total of 240 A (200 × 1.20). If the main breaker is 200 A, there is no room for a load-side connection under this rule; the installer must use a supply-side connection or a larger panel. If the main breaker is 175 A, the inverter breaker may be no larger than 65 A (240 − 175).

Back-Fed Breaker Labeling

NEC 705.12 requires the back-fed breaker in a load-side connection to be labeled "Solar" or similar, and it must be positioned at the opposite end of the busbar from the main breaker (the "line end") to reduce the chance of busbar overload at the midpoint.

Supply-Side vs. Load-Side Connections

A load-side connection uses the 120-percent rule and taps into the panelboard busbar. It is the most common approach for residential systems.

A supply-side connection taps the conductors between the utility meter and the main disconnect, upstream of the panel. Because it does not use the busbar, the 120-percent limitation does not apply; however, it requires a listed tap device and must be coordinated with the utility.

Article 706: Energy Storage Systems

Article 706 covers battery energy storage systems (BESS) that may be added to a PV installation. Key compliance points include proper disconnect means, battery area ventilation requirements, and short-circuit current ratings of equipment used with storage. When a BESS is part of the design, the permit package and inspection must address both Article 690 (the PV source) and Article 706 (the storage).

Putting It All Together

A clean permit package, a systematic inspection, and a clear understanding of Articles 705 and 706 interconnection rules are the skills that distinguish a professional installer from one who generates callbacks and failed inspections. Marking deficiencies clearly, citing the exact NEC section, and writing actionable corrections are habits that protect your employer, your customer, and ultimately the public.