Begin with the circuit being protected
List the feeder load, starting or transient demand where relevant, cable construction and installation conditions. The breaker selection should connect these inputs to the protection requirements, not begin with a preferred frame size and force the circuit to fit.
Record the actual operating voltage, supply type and prospective fault current at the feeder position. Where more than one source can supply the circuit, provide the relevant operating cases. The protection designer needs both the high-fault condition and the conditions that affect reliable fault detection and disconnection.
Keep device selection and settings traceable
| Selection input | Supplier or designer response | Record to retain |
|---|---|---|
| Continuous load | Suitable device configuration under stated ambient conditions | Offered current rating and limitations |
| Protected cable | Overload and fault-protection assessment | Cable and protection schedule |
| Fault duty | Required interruption capability at operating voltage | Device rating and applicable evidence |
| Load behaviour | Required response to normal starting or transient events | Approved protection characteristic |
| Adjacent devices | Selectivity or supported backup arrangement | Applicable coordination records |
| Optional functions | Required earth-fault, indication or remote interfaces | Included accessory and wiring schedule |
Schneider Electric's selection guidance connects circuit-breaker choice to the installation, protected conductors, environment and coordination. These factors should appear in the project response rather than being replaced by one catalogue ampere label. Circuit-breaker selection guidance.
Distinguish interruption capability from coordination
A suitable breaking rating does not by itself establish selectivity with the incomer or another downstream protective device. Request evidence for the exact device combinations and operating voltage used in the design.
If a proposal relies on an upstream device to support a downstream breaking requirement, obtain the applicable manufacturer-approved combination and its limitations. Do not infer that any two breakers from the same brand form an accepted backup arrangement. The designer should also check the protected cables and other affected components.
Example: the cable installation changes after selection
Suppose a hypothetical feeder is initially designed with one cable arrangement, then routed through a hotter or more crowded path. The load kW remains unchanged, so the purchasing team keeps the original breaker schedule without review.
The changed cable conditions can alter the protection assessment. Before manufacture, issue the revised cable information and ask the responsible designer to confirm or revise the selected device and settings. A larger breaker is not a general remedy for nuisance operation, and unchanged load power is not proof that the original protection remains suitable.
Identify the purchased trip unit and accessories
State the actual trip-unit type and adjustment capability required by the design. Record who supplies approved settings and how they are preserved at handover. Auxiliary indication, remote trip and other options should appear explicitly in the bill of materials.
IEC 60947-2 provides the applicable LV circuit-breaker standards context. The finished panel still needs its assembly review, including thermal conditions and connections. IEC 60947-2 scope.
Send the feeder and cable schedules, source conditions and coordination requirements with an LV switchgear enquiry. Request a complete panel proposal through the project contact page. MCCB model, rating, accessories and any standalone component supply require confirmation; they are not established by the cabinet family name.