to the 16th Edition IEE Regulations

chapter 5

chapter 6

  5.1 - The earthing principle 5.6 - Protective multiple earthing (PME)
  5.2 - Earthing Systems 5.7 - Earthed concentric wiring
  5.3 - Earth fault loop impedance 5.8 - Other protection methods
5.4 - Protective conductors 5.9 - Residual current devices (RCDs)
5.5 - Earth electrodes

5.10 - Combined functional and protective

5.8.2 - Non-conducting location

The non-conducting location is a special arrangement where there is no earthing
or protective system because:

1. - there is nothing which needs to be earthed

2. - exposed conductive parts are arranged so that it is impossible to touch two of them, or an exposed conducting part and an extraneous conductive part, at the same time. The distance between the parts must be at least 2 m, or 1.25 m if they are out of arm's reach. An alternative is to erect suitable obstacles, or to insulate the extraneous conductive parts.

Examples of extraneous conductive parts are water and gas pipes, structural steelwork, and even floors and walls which are not covered with insulating material. Insulation tests on floors and walls are considered in {8.5.2}. There must be no socket outlets with earthing contacts in a non-conducting location. This type of installation could cause danger if earthed metal were introduced in the form of a portable appliance fed by a lead from outside the location.

The potential reached by exposed metalwork within the situation is of no importance because it is never possible to touch two pieces of metalwork with differing voltage levels at the same time. Care must be taken, however, to make sure that a possible high potential cannot be transmitted outside the situation by the subsequent installation of a conductor such as a water or gas pipe. A notice must be erected to state that a non-conducting location exists, and giving details of the person in charge who alone will authorise any work to be undertaken in, or will authorise any equipment to be taken into, the location. If two faults to exposed conductive parts occur from conductors at different potentials (such as a phase and a neutral) and there is a defective bonding system, dangerous potential differences could occur between exposed conductive parts. To prevent this possibility, double pole fuses or circuit breakers must provide overload protection in non-conducting locations.

Non-conducting locations are unusual, and their use must be limited to situations where there is continuous and proper supervision to ensure that the requirements are fully met and are properly maintained. This type of installation should only be considered after consulting a fully qualified electrical engineer.



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Extracted from The Electricians Guide Fifth Edition
by John Whitfield
Published by EPA Press Click Here to order your Copy

Click here for list of abbreviations