Service Entrance Conductors for 200A Service: NEC Requirements, Burial Depth, and Sizing
Service entrance wire size for 200A: 2/0 copper or 4/0 aluminum under NEC 310.12 (the 83% rule). When dwelling vs commercial sizing differs.
Guides & Resources
Practical guides for electrical calculation professionals.
Arc Flash Calculations Under NFPA 70E: Incident Energy, Boundaries, and PPE Selection
Arc flash calculation under NFPA 70E: IEEE 1584-2018 incident energy, boundary, and PPE category method - with a worked 480V panelboard example.
Load Balancing a 200A Panel: Leg Assignment, Demand Factors, and Remaining Capacity
Load balance a 200A panel: measure leg current, reassign single-pole breakers, and check NEC 220.82 demand-factor math for remaining capacity.
Three-Phase Power Calculations: kVA, kW, Power Factor, and Transformer Sizing
Three-phase power calculation: kVA formula, kW vs kVA vs kVAR explained, and transformer sizing with a worked commercial example at 480V.
Motor Circuit Sizing Under NEC 430: FLA Tables, Overcurrent Protection, and Conductor Selection
Motor circuit sizing under NEC 430: conductor sizing at 125% FLC, OCPD from Table 430.52, overload at nameplate FLA. Worked example with 10 HP motor.
EV Charger Circuit Sizing Under NEC 625: Wire, Breaker, and Panel Capacity Calculations
Step-by-step EV charger circuit sizing under NEC 625: continuous load rule, wire gauge, voltage drop for long runs, and panel capacity check.
Conduit Fill Calculations Under NEC: Wire Area Tables, 40% Rule, and Common Mistakes
How to calculate conduit fill for mixed conductor sizes under NEC Chapter 9. Includes Tables 4 and 5 reference data, two worked examples with real conductor counts, the 40% fill rule, derating interactions, and common inspection failures.
Sizing a Subpanel for a Workshop: Load Inventory, Feeder Calculation, and Breaker Selection
Step-by-step guide to sizing a subpanel for a detached workshop or garage. Covers NEC load inventory, demand factors, feeder conductor sizing (copper and aluminum), voltage drop verification, overcurrent protection, and grounding requirements with worked examples.
NEC Wire Size Reference: Copper vs Aluminum Ampacity and When to Upsize
Side-by-side NEC Table 310.16 ampacity chart for copper and aluminum conductors at 60, 75, and 90 degrees C. Includes cost comparison, voltage drop worked examples, derating scenarios, and a decision framework for choosing the right conductor material.
Calculating Electrical Load for New Circuits: Continuous vs Non-Continuous Loads and NEC Rules
How to calculate electrical load for new branch circuits using NEC Article 220. Covers the 125% continuous load rule, VA per square foot tables, demand factors, and worked examples for EV charger installations and commercial lighting circuits.
Voltage Drop for Long Wire Runs: When 3% Matters and How to Calculate It
How to calculate voltage drop on long conductor runs using the NEC formula. Includes worked examples for parking lot lighting, detached workshops, and three-phase motors, plus a quick-reference distance table and strategies to reduce voltage drop.
Wire Sizing for Circuit Breakers: NEC 310 Ampacity Tables and Derating Explained
Step-by-step guide to sizing conductors for circuit breakers using NEC Table 310.16, temperature correction factors, conduit fill derating, and voltage drop calculations. Includes worked examples and a quick-reference wire-to-breaker table.