S = √(I²t) / k. The k values below are the usual ones for a conductor incorporated in a cable and not bunched with others. Confirm the right k in BS 7671 Tables 54.2 to 54.4 for the cable you are actually using. You can also type your own k.
This is the adiabatic check for the protective conductor during a fault. It is not a current-carrying-capacity calculation, and it assumes the protective device really does disconnect in the time you enter.
These tools are quick guides for a ballpark figure. They are not certified design or test software, and a result on this page is not a design, a certificate, or a substitute for the current edition of BS 7671. Check the working and cross-reference it before you apply it to a real installation. Thanet Electrical Ltd does not accept liability for loss or cost arising from reliance on these figures, except where the law does not allow that liability to be excluded, including death or personal injury caused by negligence.
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