§ Reference layer · Useful on site 4 tools live · more planned

Free tools for working UK electricians.

The reference layer. Useful on site today — and the proof that publishing beats marketing for this audience.

§ 01 · Live · Useful today Free · No account needed
Reference · Fault loop impedance Live

Max Zs Values

A public lookup for BS 7671 maximum permitted Zs values.

maxzs.co.uk Open Max Zs
Reference · RCD protection Live

RCD Disconnection Time

A public lookup for BS 7671 RCD disconnection times and protection checks.

rcddisconnectiontime.co.uk Open RCD times
Guide · Regulation reader Live

Amendment 4 Guide

Plain-English companion to BS 7671 Amendment 4, with changed regulations collected for reference.

bs7671amendment4.co.uk Open the guide
Calculator · Cable design Live

Cable Sizing Calculator

A public calculator for cable CSA, volt drop, Zs, CPC and fault-current checks.

cablesizing.co.uk Open calculator
§ 02 · Coming soon · Planned Honest · not promised
Inspection schedule Planned

EICR observation builder

Observation patterns with code classification, regulation references and remedial costing still to verify.

Code finder Planned

BS 7671 regulation finder

Free-text search across all of BS 7671 with context, amendments tracked and a canonical citation format.

Distribution boards Planned

DB schedule checker

Circuit schedules, protective device patterns and board-level consistency checks before certification.

Register interest and we'll send the link first.

Register interest Follow the build