Observed arrival · 2026-11-10
BS 7671 Site Calculator
A browser-based set of electrical installation calculators and references for UK electricians, with results that update as values are entered.
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- For
- UK electricians doing installation calculations and testing
- Worth noticing
- The Zs check compares measured values with 80% of the tabulated maximum to allow for conductor temperature rise.
Field notes
The calculators accept practical circuit inputs, including cable cross-sections, lengths, conductor temperature, and protective-device characteristics. Results can be carried between sections: the page offers a control to use an R1+R2 value in the Zs check. Its reference material includes copper resistance figures and device-specific trip-current assumptions; the extracted evidence does not independently verify those values against the applicable standard.
Observed signals
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Editorial observations of this landing page, not a rating.
○OpenPublic substance visible
✦PrettyNotable craft visible
●ProPolished or operationally mature
◎NicheUnusually specific use
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