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NEC Ch.9
Validated against the standard.
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How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact NEC Ch.9 reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
PV wiring runs in conduit just like any other circuit, and the same NEC fill limits apply. This app checks conduit fill for PV conductors against NEC Chapter 9, so your DC home-runs, EGCs, and AC circuits fit the raceway legally.
The fill limits (Chapter 9, Table 1)
| Conductors | Max fill |
|---|---|
| 1 conductor | 53% |
| 2 conductors | 31% |
| 3 or more | 40% |
Conductor areas come from Table 5 and conduit interior areas from Table 4 — the app stores both and adds the equipment grounding conductor.
Worked example
Four #10 PV wire conductors plus a #10 EGC in 1/2-inch EMT: the app sums the areas and confirms the total stays under the 40% fill limit, or recommends 3/4-inch if it does not.
Related calculators
Size the conductors with the solar wire sizing calculator and check loss with the solar voltage drop calculator.
Solar conduit fill FAQ
Are PV conduit fill rules different?
No — the same NEC Chapter 9 fill percentages apply: 53% for one conductor, 31% for two, and 40% for three or more. PV just tends to run several current-carrying conductors together.
Does it include the grounding conductor?
Yes. The equipment grounding conductor takes up space too, so the app includes it in the total fill.
Which conduit types are supported?
EMT, IMC, RMC, and PVC in standard trade sizes, using the interior areas from Chapter 9 Table 4.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
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