Equipment for General Use
Chapter 4 Scope
Chapter 4 covers flexible cords and cables (400), fixtures and lampholders (410), receptacles and switches (404, 406), switchboards and panelboards (408), industrial controls (409), motors (430), air conditioning (440), generators (445), transformers (450), capacitors (460), storage batteries (480), and appliances (422).
Concepts to Master
- Flexible cords: permitted uses and prohibited uses (no substitutes for fixed wiring, no running through walls or ceilings).
- Receptacles: grounding-type requirements, GFCI protection locations, tamper-resistant requirements, and ratings matched to branch circuits.
- Motors (Article 430): motor branch-circuit conductor sizing (125% of FLC), overload protection separate from short-circuit protection, and disconnect requirements.
- Transformers (Article 450): overcurrent protection on primary and secondary, and ventilation requirements.
- Panelboards (Article 408): working clearance, dedicated spaces, and labeling.
Traps
- Confusing motor overload protection with branch-circuit short-circuit and ground-fault protection; they serve different purposes.
- Forgetting that flexible cords cannot be used as a substitute for permanent wiring.
- Missing GFCI requirements in specific locations (bathrooms, kitchens, outdoors, garages).
- Assuming transformer protection is only on the primary.
Worked Example
A motor has a full-load current of 20 A. Branch-circuit conductors are sized at 125%, giving 25 A, while overload protection is based on the motor's service factor or temperature rise per tables. Rule of thumb: conductors and short-circuit protection size to motor FLC with 125%, overloads size to the motor's thermal limits.
Rule of Thumb
Motors need three separate considerations: conductors, short-circuit protection, and overload protection. Never collapse them into one calculation.