Clamps, earthing and bonding

The scope of BS 951: 2009 states that the clamps are primarily intended for use in electrical installations for:

Clamps installed on pipes to a central heating boiler

The termination on a BS 951 clamp for the protective conductor is separate from the means of tightening and locking the clamp for making electrical contact with the tube.

A screw termination is capable of accepting one of the following:

Clamps having terminations in accordance with i or ii above are marked with the appropriate termination reference in accordance with Table 1 of BS 951. The limits of the range are presented in the form ‘X-Y’, where X is the reference of the smallest acceptable conductor and Y is the reference of the largest acceptable conductor. In addition, for clamps having provision for terminations in accordance with i or ii, it must be possible to loop in and out an unbroken conductor.

Clamps manufactured to BS 951 are made in a choice of different metals, to suit differing levels of corrosion that are likely to be encountered in service. In order to comply with the requirements of Section 522 of BS 7671, it is important to select a clamp which is suitable for the expected conditions in the particular location where it is to be installed.

Earth clamps come in three common types and conform to BS 951.

E14 clamps are for dry conditions only and are often coloured red.

E15 clamps are for dry or damp conditions and are often coloured blue.

E16 clamps are for dry, damp or corrosive conditions and are often coloured green.

The E16 clamps allow for a larger conductor (usually 16mm² or greater) to be connected than for E14 and E15 clamps.

Like all types of electrical connection that are not excused by Regulation 526.3 of BS 7671, the electrical connections between a BS 951 clamp, the pipe (or other tube) to which it is attached, and the protective conductor connected to its terminal must be accessible for inspection, testing and maintenance (Regulation 543.3.2 refers).

For other guidance and publications please see the ELECSA website. Information about the ELECSA Domestic Installers schemes, visit www.elecsa.co.uk

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