Wire and conduit schedules on solar plans
The schedule is where a reviewer checks your arithmetic. The diagram shows what connects to what; the schedule proves each conductor can carry its load, survive its environment, and fit its raceway.
The five columns that matter
| Column | What it proves |
|---|---|
| Circuit / from → to | Which run this is, unambiguously |
| Conductors | Count and function — permitted wiring method (690.31) |
| Size · material · insulation | Ampacity from Table 310.16 at the right column |
| EGC | Sized from the OCPD per 250.122 |
| OCPD · raceway | 240.4 protection and Chapter 9 fill |
Ampacity is three checks, not one
A conductor passes when it survives all three, and reviewers check all three:
1. Table 310.16 base ampacity at the correct insulation column. 2. Corrections and adjustments — 310.15(B)(1) ambient and 310.15(C)(1) for more than three current-carrying conductors. 3. Termination temperature — 110.14(C) caps you at the 60 °C or 75 °C column regardless of the wire's own rating.
State the ambient you used and the number of current-carrying conductors. A derated ampacity with no stated conditions is a number a reviewer cannot verify.
Conduit fill, stated rather than implied
Chapter 9 Table 1 caps fill at 53% for one conductor, 31% for two, and 40% for more. The check needs conductor areas (Table 5) and raceway area (Table 4) — and PV wire is thicker-walled than THWN, which catches people out.
Put the trade size on the sheet. "3/4" EMT" is checkable; "conduit as required" is a correction.
Where schedules go wrong
- Disagreeing with the diagram. The single most common finding. If the one-line says 8 AWG and the schedule says 10 AWG, both are now suspect.
- Quantities that do not match. A 26-module array is QTY 26 in the equipment schedule, not QTY 1.
- Missing EGC. Present in the raceway, absent from the table.
- Ambient not stated. Rooftop conduit runs hot; a schedule computed at 30 °C for a run in the sun above a roof will be questioned.
- Parallel sets shown as one conductor. If it is two runs, say two runs — 310.10(H) has rules about it.
The structural fix
Most schedule errors are consistency errors, and consistency errors come from maintaining the same fact in two places. When the schedule is generated from the same typed model that draws the diagram, they cannot disagree — change a breaker and the wire size, EGC and conduit all move together.
That is how OneLine Studio builds Sheet 6: the equipment, circuit and panel schedules are rendered from the design, not typed alongside it, and every size comes from the same NEC engine that annotates the one-line.
See also: sizing conductors and breakers and Chapter 9 conduit fill.
> Design aid — a licensed electrician or PE must review and stamp before filing.
FAQ
What is a conductor schedule on a solar plan?
A table listing every circuit with its conductors, size and material, equipment grounding conductor, overcurrent device and raceway, so a reviewer can check ampacity and fill without measuring the drawing.
Does a solar permit need a conduit schedule?
Most AHJs expect raceway type and trade size stated per run, either in the schedule or annotated on the one-line. Chapter 9 fill cannot be checked without it.
What is the most common conductor schedule error?
A schedule that disagrees with the diagram — a wire size shown one way on the one-line and another in the table.
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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