17th Edition Inspection Testing Policies

Electrical Services Inspection and Testing Requirements

Electrical installations in premises are common causes of fires and can also cause injury or fatality. The majority of fires of electrical origin occur due to defective installation, inadequate maintenance or misuse of electrical systems and apparatus.

The installation, use and maintenance of electrical installations are governed by the Electricity at Work Regulations 1989 which requires all electrical systems to be maintained to a safe standard. Periodic inspection and testing of electrical installations at premises by a qualified electrician can assist with compliance and should be undertaken in accordance with BS7671 "Requirement for Electrical Installations" (IEE Wiring Regulations 16th Edition) and supporting IEE Guidance note 3. The frequency of the testing is dependant on the type of premises and varies between one and ten years.

For guidance, a typical inspection and testing will involve the following;

Distribution Boards and Final Circuits
     • 100% of distribution boards undergo visual inspection
     • 100% of distribution boards are tested for Earth Loop Impedance and short circuit current
     • Approximately 10% of lighting circuits are tested for insulation resistance
     • Approximately 20% of power circuits are tested for insulation resistance
     • 10% of the final ring circuits are tested for insulation
     • A light fitting within each circuit is tested for insulation resistance and internal inspection
     • 100% of light circuits are tested for insulation resistance and given an Earth Loop  
Impedance test at the furthest point in the circuit
     • Additional samples of 5% of all light fittings are given Earth Loop Impedance test
Mains Socket Outlets
     • 100% of sockets will receive an external inspection
     • 100% of socket outlets will be tested for Earth Loop Impedance and polarity
Fixed Appliances (not operated from control panels)
     • 100% of fixed appliances receive an external inspection, 10% internal inspection
     • 100% of fixed appliances are tested for Earth Loop Impedance
     • 10% of fixed appliances are tested for insulation resistance
Fixed Appliances (operated from a control panel)
     • 100% of control panels are inspected internally wherever possible
     • Earth Loop Impedance tests are performed at each control panel and at each appliance 
fed from the panel wherever possible
     • A 10% sample of electrical terminations inside control panels will be checked for tightness
Residual Current Devices
     • 100% of RCDs are tested for tripping times at half rated, full rated and 5 times rated tripping
current across both positive and negative cycles
Main Switchgear and Circuits
     • 20% of all circuits from the main switchgear to the local distribution plant are inspected
and tested for the following;
               • Insulation resistance
               • Main switchgear is inspected internally
               • Cable sizes are checked for current carrying capability
               • Circuit protective devices are checked for deterioration
               • Earth Loop Impedance and prospective short circuit current are measured
     • 100% of circuit wiring is, where possible and relevant, visually inspected

The inspection and test should be undertaken by a qualified electrician or contractor, preferably by a member of the National Council for Electrical Installation Contacting  (NICEIC), Electrical Contractor Association (ECA) or someone approved by a UKAS/ISO17020 accredited organisation.