Quick Hits

Episode 7 — OCPD Types, Parallel Devices, and Supplementary Protection

Covers: 240.7, 240.8, 240.9, 240.10

Hook: What actually counts as a legal OCPD? And can you run two fuses side by side to double the rating? Let's clear that up.

Slide 2: Legal OCPDs include molded-case breakers, low-voltage power breakers, solid-state/hybrid breakers, the full alphabet of fuse classes (C through T), Edison-base and Type C/S fuses, and anything else labeled suitable for the application.

Slide 3: Fuses or breakers can only be paralleled if they're factory-assembled and listed as a single unit — you can't just wire two individual devices side by side on your own. Thermal-only relays (not designed to clear short circuits/ground faults) can't serve as short-circuit protection, though they're fine for motor overload protection under 430.40. Supplementary OCPDs (protecting internal equipment components or individual fixtures/appliances) can't substitute for required branch-circuit protection, and they don't have to be readily accessible.

Quiz: Can two individually purchased circuit breakers be field-wired in parallel to increase capacity?
Answer: No — only fuses/breakers factory-assembled and listed as a parallel unit are permitted.

CTA: Follow — selective coordination and ground-fault protection are next.

← View Chapter 2 Home

← Back To Article 240 Home

← Back To Quick Hits Home