Check k-factor assumptions
The adiabatic shape depends heavily on conductor material, insulation type and initial/final temperature assumptions. Use the right k value before trusting the margin.
Electrical calculator · CPC / adiabatic / fault current / BS 7671
CPC Adiabatic Equation Calculator
Use the adiabatic equation shape to compare fault current, disconnection time, k factor and CPC size as a planning aid.
For competent review of CPC adequacy where final design still needs current BS 7671 tables and site data.
Field notes
Field notes for CPC adiabatic
Practical checks to run before this calculator result turns into a site decision.
Fault time matters
A small change in disconnection time can change the CPC result. Check the protective device data rather than guessing a convenient duration.
Use it as a review flag
If the result is close, escalate to proper design review. This page is built for triage and conversation, not final certification.
FAQ
CPC adiabatic FAQ
Short answers written for UK temporary electrical and HVAC planning work.
What is the CPC adiabatic used for?
Use the adiabatic equation shape to compare fault current, disconnection time, k factor and CPC size as a planning aid. 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. It is a competent-person planning aid only. 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 permission to energise.
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 reviewed by a competent electrician before use.
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