/ Field knowledge · NEC 100 · Sparky Edition
The breaker rating is not the package SCCR.
NEC Article 100: a feeder can be sized for load while the equipment at its end is unsuitable for the fault current available there. The breaker interrupting rating is not the package SCCR.
Educational 2026 NEC Article 100 terminology. Confirm the adopted edition. This is not a fault study and not a series-rated design. Compare the same voltage and rating basis.
- Available fault current — what the supply can deliver at a particular point under the evaluated fault condition.
- SCCR — an equipment assembly’s suitability for prospective fault current under its specified conditions.
- Interrupting rating — a breaker or fuse’s ability to interrupt current at its applicable voltage and test conditions.
None of those three is the normal operating load current. For a fully rated arrangement, available fault current at the connection must not exceed the applicable equipment SCCR or protective-device interrupting rating. A large interrupting rating printed on a breaker does not automatically give the surrounding control panel, VFD, pump package, or HVAC assembly that SCCR.
Illustrative review from Daily Code Talk — not a design calculation: a verified study identifies 22 kA available at a package; the nameplate says 10 kA SCCR; the supply breaker is 65 kA interrupting. The breaker’s rating does not close the package mismatch. Hold procurement. Do not relabel the assembly from this example.
Do not improvise a series-rated solution
Do not subtract a fuse’s advertised let-through from available current. Changing a specified protective device can invalidate a conditional rating. Missing or illegible SCCR is unresolved evidence, not a zero-risk condition. An arc-flash label and an SCCR evaluation answer different questions.
Source: Sparky SCCR · tool: SCCR screen · grounding: bonding.
What to send
The one-line, the package nameplate photo (safe access only), and the fault-current value at the actual connection if a study exists.
If the VFD is 10 kA and the service is larger
Send the nameplate and the study page. Masterbuild will say whether SCCR is even documented — or the breaker IR was used as a substitute.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Sparky Edition uses the 2026 NEC as model-code education. Confirm the adopted edition. Field observations do not establish electrical safety; only qualified personnel using required safe-work procedures should access electrical equipment.