A practical NEC Article 392 cable tray design guide — tray types, fill calculations for single conductors vs. multiconductor cable, support spacing, grounding/bonding as an equipment grounding conductor, and power/low-voltage separation. Cable tray sizing looks simple on paper, but in real projects it affects cable safety, thermal performance, maintainability, future expansion, and inspection approval. It also provides practical sizing logic and real-world considerations so you can avoid common design mistakes and build. Selecting the right cable tray size is critical for electrical safety, system efficiency, and cost control.