PRELIMINARY ENGINEERING TOOL
Preliminary breaker-size helper
Find a nominal standard rating that satisfies the basic Ib ≤ In ≤ Iz relation.
Inputs
Calculation steps
Ib = 25 A × 1 = 25.00 A
25.00 A ≤ 25 A ≤ 32.00 A
Formula ID: BREAKER_SUGGESTION_V2
Assumptions and references
Preliminary calculation only. Verify inputs, manufacturer data, applicable standards, fault levels, and local requirements before construction or procurement.
Check the current relationship in context
See how corrected cable capacity changes the Ib ≤ In ≤ Iz comparison, and why it does not complete protection design.
Read three breaker and cable examples →UNDERSTAND THE TOOL
What this calculator does
Identify ratings in your selected series that satisfy the narrow relationship between design current, nominal breaker rating and corrected cable capacity.
How to use it
- Enter design current and corrected cable capacity.
- Confirm the rating series and descriptive pole/curve inputs.
- Review the candidate relation.
- Complete fault, breaking-capacity and coordination studies separately.
Fields and meanings
- Ib
- Expected design current.
- Iz
- Corrected cable current-carrying capacity.
- Rating series
- Nominal breaker ratings available for comparison.
- Poles and curve
- Descriptive inputs only; they do not complete protection design.
Review required. Breaking capacity, fault protection, RCD requirements, selectivity and coordination are not solved here.
Read the full explanation →