Raceway / Cable Support-Spacing Lookup (NEC Chapter 3)
The securing and support intervals for the common wiring methods from their NEC Chapter 3 .30 sections.
Example
You enter
- Wiring method EMT
You get
- Secure within (of each box) 36 in
- Maximum support interval 10
Details, formula, and sources
EMT within 3 ft of a box and every 10 ft, NM within 12 in and every 4.5 ft, MC within 12 in and every 6 ft, AC within 12 in and every 4.5 ft; RMC and PVC intervals vary with trade size. The securing exceptions (fishing, terminations) and the AHJ govern.
by wiring method: EMT secure within 36 in, support every 10 ft (358.30); NM within 12 in, every 4.5 ft (334.30); MC within 12 in, every 6 ft (330.30); AC within 12 in, every 4.5 ft (320.30); RMC/PVC intervals vary with trade size.
Securing and supporting sections of NEC 2023 Chapter 3 (320.30, 330.30, 334.30, 344.30, 352.30, 358.30), by name.
NEC is free to read at nfpa.org/freeaccess. RMC and PVC maximum intervals vary with trade size (the size-specific tables govern); some methods have securing exceptions (fishing, terminations).
Estimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
Field names used by the API: wiring_method, secure_within_in, max_interval_ft
- Per-method intervals EMT 3 ft / 10 ft; NM 12 in / 4.5 ft; MC 12 in / 6 ft; AC 12 in / 4.5 ftNEC 358.30, 334.30, 330.30, 320.30
- Size-dependent conduit RMC (344.30(B)(2)) and PVC (352.30) maximum intervals increase with trade sizeNEC Tables 344.30(B)(2) and 352.30