Breaker Selectivity: Coordinating Main and Final-Circuit Breakers
Selectivity (discrimination) means the upstream breaker and each downstream breaker in a panel are matched so a fault on one final circuit trips only that circuit -- not the shared incomer that would black out everything else. It's achieved through rating and/or time coordination between devices, following the manufacturer's published selectivity tables for that specific combination. We treat it as a design decision made per project, not a fixed rule to assume by default.
How we coordinate selectivity in a panel
Map the circuit hierarchy
We identify the incomer/main breaker and every downstream final-circuit breaker it feeds, so the coordination chain is clear before any device is selected.
Check manufacturer selectivity tables
Selectivity between two specific breaker models and ratings is documented by the manufacturer, not assumed -- we consult the published tables for the actual devices in the design.
Coordinate rating and/or time settings
Devices are matched by current-rating step, time-delay setting, or both, so the downstream breaker clears a final-circuit fault before the upstream device has a chance to react.
Record the coordination in panel documentation
The verified breaker combination and its selectivity basis go into the handover documentation, alongside the panel's IEC 61439 records.
Why selectivity matters to whoever operates the panel
A local fault stays local
With correctly coordinated breakers, a fault on one final circuit trips only that circuit's breaker -- the rest of the installation keeps running.
Fewer unnecessary blackouts
Poor selectivity means one faulty appliance or cable on a minor circuit can trip the main breaker and cut power to the entire panel.
A design decision, not a checkbox
The right selectivity level depends on the specific breakers chosen for that project -- we treat it as an engineering choice, not a universal default.
Based on manufacturer data, not assumption
We work from the manufacturer's published selectivity (discrimination) tables for the actual device combination, rather than estimating.
A distinct topic from surge and leakage protection
Selectivity is not the same discussion as SPD placement or RCD type selection -- those are separate concerns covered on their own pages.
Documented for future maintenance
The coordination basis is recorded so anyone servicing the panel later understands why specific breakers were paired the way they are.
What's included when selectivity is part of your panel build
Selectivity coordination is folded into the same engineering process as the rest of the panel -- it isn't a separate add-on step.
- Circuit hierarchy review
- Manufacturer selectivity table check
- Coordinated breaker rating/time selection
- Selectivity basis recorded in handover documentation
- Alignment with IEC 61439 verification records
Frequently asked questions
What does breaker selectivity (discrimination) actually mean?
It means the upstream (main/incomer) breaker and each downstream (final-circuit) breaker are chosen and coordinated so that a fault on one final circuit trips only that circuit's breaker, not the shared upstream device.
Is selectivity the same thing as surge protection or RCD type?
No. Selectivity is about breaker coordination during a fault; surge protection (SPD) is a separate protection concept, and RCD type selection is its own topic -- see our other pages for those.
Does every panel need full selectivity?
It depends on the project -- how critical continuity of supply is for the unaffected circuits, and what the manufacturer's tables allow for the breakers chosen. We discuss this with you as part of the design.
How do you choose which breaker combination gives selectivity?
From the manufacturer's published selectivity tables for the specific breaker models and ratings involved -- not a generic rule of thumb, since it varies by manufacturer and series.
Can selectivity be improved on an existing panel?
Sometimes, by changing one or more breakers to a combination the manufacturer confirms is selective -- whether that's practical depends on the existing installation and is best assessed per project.
Talk to us about selectivity before we build your panel
Send us your single-line diagram or circuit list and we'll flag where breaker coordination needs attention.