Panel schedules and circuit directories
The panel schedule looks like paperwork. It is actually where several NEC requirements land at once — identification, interconnection, and the arithmetic that decides whether your PV breaker can be in that panel at all.
What 408.4 actually asks for
Circuits must be identified by clear, evident and specific purpose. "Lights" is not specific. "Kitchen lighting" is. The directory lives on the panel face or inside the door, and it must be legible — a handwritten pencil note that has faded is a finding.
408.4(B) adds that the panelboard must be marked with the source supplying it, which matters once a PV system is present and the panel has more than one.
The back-fed breaker is not a load
Show it as a source. Three things belong with it:
- Placement at the opposite end of the busbar from the main, which is what 705.12(B)(3)(b) requires for the 120% allowance.
- The label — "POWER SOURCE OUTPUT — DO NOT RELOCATE THIS OVERCURRENT DEVICE".
- A dual-source marking on the panel, so nobody assumes de-energising the main kills the bus.
Put the busbar arithmetic on the schedule
This is the part reviewers appreciate. State:
| Value | Example |
|---|---|
| Busbar rating | 200 A |
| x 1.2 allowance | 240 A |
| Main breaker | 200 A |
| Back-fed OCPD (all sources) | 40 A |
| Sum vs allowance | 240 A ≤ 240 A — passes |
Two points that catch people: every grid-interactive source on the bus is summed, not just the PV inverter — add an AC-coupled battery and the sum changes. And a dwelling service disconnect cannot go below 100 A (230.79(C)), so "shrink the main" is not always an available fix. See the 120% rule.
Common findings
- Directory blank or generic. "Spare" on a circuit that is in use.
- Back-fed breaker listed as a load. Reads as though the panel has no second source.
- Bus rating absent. The reviewer cannot check 705.12 without it.
- Schedule contradicts the one-line. Different main breaker size in two places.
- No dual-source placard where the panel is fed from both directions.
Generate it, do not retype it
A panel schedule maintained by hand drifts from the design the first time someone changes a breaker. OneLine Studio renders the panel schedule from the same model that draws the one-line and runs the 705.12 check, so the bus rating on the schedule and the bus rating in the arithmetic are the same number by construction.
See also: solar and your electrical panel and NEC 690.56 labels and placards.
> Design aid — a licensed electrician or PE must review and stamp before filing.
FAQ
What does NEC 408.4 require?
Every circuit and modification must be legibly identified as to its clear, evident and specific purpose, on a directory located on the face or inside the panel door.
How is a back-fed solar breaker shown on a panel schedule?
As its own circuit, identified as a power source rather than a load, with the label required by 705.12(B) and placed at the opposite end of the busbar from the main.
Does the panel schedule need to show the busbar rating?
It should. Bus rating, main breaker and back-fed breaker together are what prove the 120% rule, and a reviewer wants them in one place.
Related: Drawings & documentation
Educational reference, reviewed 2026-07. A design aid, not a substitute for a licensed electrician or PE. Confirm the enforced NEC edition and local amendments with your AHJ.
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