What does NEC Section 240.21(C) cover?

What does NEC Section 240.21(C) cover?

• A. Feeder taps
• B. Full load current for motors
• C. Transformer secondary conductors
• D. Outside taps unlimited length

Answer: (C)

This section focuses on the protection and sizing of transformer secondary conductors. The secondary conductors are the wires on the low‑voltage side of a transformer—the lines that deliver the transformed power to the downstream circuits. NEC 240.21(C) sets requirements to ensure these conductors are protected by an overcurrent device and sized appropriately for the load on the transformer’s secondary, so the conductors aren’t under- or overprotected. In practice, this means the overcurrent protection on the secondary side must be chosen to protect the secondary conductors themselves, based on their ampacity, while also considering the transformer’s secondary rating. This is distinct from feeder taps or motor full‑load current calculations, which are addressed by other sections and articles of the NEC. It’s also not about “outside taps of unlimited length,” which isn’t a valid provision in this context. So, transformer secondary conductors are what NEC Section 240.21(C) covers.

This section focuses on the protection and sizing of transformer secondary conductors. The secondary conductors are the wires on the low‑voltage side of a transformer—the lines that deliver the transformed power to the downstream circuits. NEC 240.21(C) sets requirements to ensure these conductors are protected by an overcurrent device and sized appropriately for the load on the transformer’s secondary, so the conductors aren’t under- or overprotected.

In practice, this means the overcurrent protection on the secondary side must be chosen to protect the secondary conductors themselves, based on their ampacity, while also considering the transformer’s secondary rating. This is distinct from feeder taps or motor full‑load current calculations, which are addressed by other sections and articles of the NEC. It’s also not about “outside taps of unlimited length,” which isn’t a valid provision in this context.

So, transformer secondary conductors are what NEC Section 240.21(C) covers.