Conduit Jam Ratio for Three Same-Size Conductors (NEC Ch. 9)
Three same-size conductors can wedge in a bend when the conduit ID / conductor OD ratio lands in the ~2.8-3.2 band.
Example
You enter
- Conduit inside diameter (in, NEC Ch.9 Table 4) 2.067
- Conductor outside diameter (in, Table 5) 0.65
- Number of conductors 3
You get
- Ratio 3.18
Details, formula, and sources
Three 0.65 in conductors in 2 in EMT (ID 2.067) -> ratio 3.18, jam-prone; 3.22 is just clear. Jamming needs exactly three conductors. A pull caution, not a code limit; the NEC and AHJ govern.
ratio = conduit_ID / conductor_OD; jam-prone if n = 3 AND 2.8 <= ratio <= 3.2.
The conduit-jamming ratio guideline referenced with NEC Chapter 9 (Table 4 conduit ID, Table 5 conductor OD), by name.
The jam-ratio guideline is a widely-published cable-pulling rule; the conduit ID and conductor OD are in NEC Chapter 9 Tables 4 and 5 (NFPA 70). The NEC and the AHJ govern.
Estimate. AHJ and licensed professional govern.
Field names used by the API: conduit_id_in, conductor_od_in, n_conductors, ratio
- Jam band jam-prone when exactly three conductors and 2.8 <= ID/OD <= 3.2cable-pulling guideline / NEC Ch. 9
- Table dimensions conduit ID from NEC Ch. 9 Table 4; conductor OD from Table 5NEC (NFPA 70) Chapter 9
- A caution, not a limit a pull caution; does not check fill area or pulling tensionscope of this tile