Equipment and Systems
This chapter covers how the Code sizes conductors and protection for specific loads and systems, from motors and HVAC to transformers, lighting, generators, solar, pools, and low-voltage work. Each equipment type has its own article with sizing multipliers and protection rules that override the general wiring chapters.
Motors (Article 430)
Motor circuits are unusual because the conductor, the overload device, and the branch-circuit short-circuit protection are each sized differently and from different tables. Conductors are sized from the motor's full-load current value in the Code tables rather than the nameplate current, while overloads protect from the nameplate. Understanding which value feeds which calculation is the key to passing motor questions.
HVAC and Air Conditioning (Article 440)
Sealed hermetic-motor equipment such as air conditioners and heat pumps uses its own article that layers on top of the general motor rules. The nameplate provides two engineered numbers, the minimum circuit ampacity and the maximum overcurrent protection, that installers must respect exactly rather than calculating from scratch.
Transformers and Lighting (Articles 450 and 410)
Transformers are protected on the primary and sometimes the secondary using percentage limits that depend on the protection scheme chosen. Luminaires and their wiring follow Article 410, which governs support, clearances from combustibles, and the temperature rating of conductors entering fixtures.
Generators, Standby, and Transfer Switches (Articles 445, 700, 702)
Standby and emergency power systems combine a source such as a generator with a transfer switch that prevents the utility and generator from ever being connected at the same time. Emergency systems that protect life safety carry stricter wiring separation and testing rules than optional standby systems that merely serve convenience loads.
Solar, Pools, and Low-Voltage (Articles 690, 680, 725, 760, 800)
Special systems each add their own protections layered on the general Code. Photovoltaic arrays manage direct-current strings and rapid shutdown, swimming pools rely on equipotential bonding to eliminate voltage gradients, and Class 2 and communications circuits use power-limited sources that change the wiring and separation rules.
Last updated: July 2026