Code Applied by the app elec.conduit.fill-limit
Conduit fill limits
How much of a raceway's inside area conductors may fill — 53% for one, 31% for two, 40% for three or more.
| When | The app uses |
|---|---|
| 1 conductor | 53 % |
| 2 conductors | 31 % |
| 3 or more conductors | 40 % |
- Source
- NEC · Chapter 9, Table 1 · read the public text
- Editions checked
- 2017 · 2020 · 2023
- Used by
- Bid Check
- Amendments
No state or local amendment to this rule is on file. Not on file means the model code as written — check your jurisdiction.
A model code the authority having jurisdiction adopts.
A raceway is only allowed so full. The limit is a share of the conduit's inside area, and it depends on how many conductors share the run: one conductor may take 53%, two may take 31% between them, and three or more may take 40% together. Nearly every branch run on a plan is the 40% case.
What the app does with it
The Conduit fill within the table limit row in Bid Check adds up the conductors on every run of a line type — the ones you wrote on the type (2 #12 THHN + 1 #12 G) or on the run — takes their areas from the insulation family and gauge, divides by the raceway's inside area, and compares with this limit. When a run fails, the row names the smallest trade size of the same raceway that passes.
The conductor and raceway areas come from Chapter 9 Tables 4 and 5 and stay in code, cited there; they are not reprinted on this site.
What it does not do
It does not apply the 60% nipple allowance, derate for ambient temperature or bundling, or check a cable assembly (MC, NM) — those carry their conductors inside and are counted as one cable row instead.
Cited by section, not reprinted: the code text belongs to its publisher. Company practice is not a rule here — it lives with your pricing.