Improper breaker sizing can cause fires, equipment damage, or electrical shock. This calculator provides guidance only. Always consult local electrical codes and hire a licensed electrician for installations.
Load current used by the selected screening path.
• Evidence: Primary numeric rule pending · screening only
If wire is already installed, check coordination
Actual conductor insulation only. It is the derate base; it is not the final termination limit.
Missing information conservatively blocks the next-size-up permission.
The selected device rating is used as the circuit ampere rating for the termination rule. The wire check then verifies that fixed rating; it never guesses a ≤100 A or >100 A category.
A separate listed connector stacks an additional ceiling under 110.14(C)(2).
Select the actual conductor insulation rating before checking wire coordination.
— AWAITING INPUT —
Enter load information to calculate
- • Apply ambient and current-carrying-conductor factors first
- • Next-size-up at or below 800 A requires all three recorded conditions
- • Above 800 A, conductor ampacity must be at least the device rating
- • The motor/device matrix percentage is a maximum, not a minimum
- • Default selection is the largest standard rating not exceeding that maximum
- • Next-higher and starting increases are explicit, separately bounded exceptions
- • Material- and size-specific OCPD ceilings are enforced
- • Limits are checked after applicable correction factors
- • Table 310.16 ampacity remains distinct from the OCPD ceiling
- • Motor FLC table cells are pending; entered FLC stays screening-only
- • HVAC 440.22 and welder 630.12 numeric rules remain pending
- • Separate motor overload sizing is outside this SCGF result
• Coordinate the selected device with corrected conductor ampacity and every applicable exception
• Always follow local electrical codes
• Use GFCI/AFCI where required by code
• Label all circuits at panel
• Hire licensed electrician for installations