Separate PSCC and PEFC thinking
Use the measured or declared Ze and voltage to sanity-check fault-current magnitude, then compare the result with the actual device breaking capacity on that board.
Electrical calculator · PFC / PSCC / PEFC / fault current / Ze
Prospective Fault Current Calculator UK
Estimate PSCC or PEFC from Ze and voltage, compare against device breaking capacity, and draft a quick test-sheet note.
For electricians checking prospective fault current, breaking capacity and temporary distribution assumptions.
Field notes
Field notes for PFC / fault current
Practical checks to run before this calculator result turns into a site decision.
Do not hide behind a rounded number
If the result sits close to device capacity, verify supply characteristics and manufacturer data rather than rounding it down for a tidy test-sheet note.
Good for temporary DB reviews
The result is useful when deciding whether a temporary board, generator-fed setup or hired distribution package needs closer review before energising.
FAQ
PFC / fault current FAQ
Short answers for UK temporary electrical and HVAC planning.
What is the PFC / fault current used for?
Estimate PSCC or PEFC from Ze and voltage, compare against device breaking capacity, and draft a quick test-sheet note. It is mainly for UK electrical review work, especially where a quick pre-check is needed before selecting equipment or changing a temporary setup.
Can this replace BS 7671 design, inspection or testing?
No. Treat it as a pre-check for the conversation or job file. Final decisions still need current BS 7671 requirements, manufacturer data, inspection, testing, risk assessment and the actual site conditions.
What should I verify before acting on the result?
Check current BS 7671 values, manufacturer device data, measured results, earthing arrangement, correction factors and site installation conditions. If any assumption is uncertain, use the result as a prompt to investigate rather than as clearance to switch on.
What does an amber or red result usually mean?
It normally means the margin is weak, an assumption is missing, or the load should be split, staged, moved closer to the supply, reduced or checked by a qualified electrician before use.
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