Periodic Inspection and Testing of the fixed wiring is necessary because all electrical installations will deteriorate over time due to a number of factors such as damage, wear, tear, corrosion, excessive electrical loading, ageing and environmental influences. Consequently:
- Legislation requires that electrical installations are maintained in a safe condition and therefore must be periodically inspected and tested.
- Licensing authorities, public bodies, insurance companies, mortgage lenders and others may require periodic inspection and testing of electrical installations, as is for example the case for houses in multiple occupation (HMOs)
- Additionally, periodic inspection and testing should be considered:
- to assess compliance with BS7671
- on a change of occupancy of the premises
- on a change of use of the premises
- after alterations or additions to the original installation
- because of any significant change in the electrical loading of the installation
- where there is reason to believe that damage may have been caused to the installation, as might be the case for example after flooding.
The frequency of periodic inspection and testing depends on: the type of installation, its use and operation, the frequency and quality of maintenance and the external influences to which it is subjected. The IEE Guidance Note 3 (Inspection and Testing) recommends initial intervals which vary from 3 months to 10 years, but allows for future inspection and testing intervals to be increased or decreased depending on the condition of the installation.