Neither BS 7671 nor the Guidance Notes are design guides. It is essential to prepare a full specification prior to commencement or alteration of an electrical installation. The specification should set out the detailed design and provide sufficient information to enable competent persons to carry out the installation and to commission it.

The specification must include a description of how the system is to operate and all the design and operational parameters. It must provide for all the commissioning procedures that will be required and for the provision of adequate information to the user. This will be by means of an operational manual or schedule.

It must be noted that it is a matter of contract as to which person or organisation is responsible for the production of the parts of the design, specification and any operational information.