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Getting Started: Inspection & Testing

Purpose

This section is a practical reference for inspecting and testing low voltage electrical installations: new work, alterations and additions, and periodic inspection. It explains the order of the tests, how to carry each one out, what a normal reading looks like, and how to isolate safely before you start.

It supports the standards. It does not replace them.

The Standards That Govern It

  • BS 7671 (the Wiring Regulations), Part 6, sets out the inspection and testing requirements and the acceptable results.
  • IET Guidance Note 3 (GN3) explains how to carry out each test and in what order.
  • IET On-Site Guide gives the tables most often needed on site, including expected R1+R2 values.
  • Electricity at Work Regulations 1989 and HSE GS 38 cover safe working and test equipment.

Always work from the current editions.

Habits That Keep Results Reliable

  • Inspect before you test. A visual inspection comes first.
  • Isolate safely every time. See Safe Isolation.
  • Use approved test equipment. Check it is in date and undamaged. Null the test leads before continuity tests. Record the tester serial number and calibration date.
  • Work in the right order. Dead tests first, then live tests. See Sequence of Tests.
  • Write results down as you test. Fill in the Schedule of Test Results as each test is done, not from memory afterwards.
  • Check every reading. Compare it with what you expect and with the limits in BS 7671 before moving on. See Expected Readings.
  • Put everything back. Anything disconnected for a test must be reconnected and tight before the supply is restored.

Where to Go Next

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