SCHOOL OF PHYSICS GENERAL SAFETY GUIDELINES FOR CONSTRUCTING ELECTRONIC AND ELECTRICAL RESEARCH EQUIPMENT

The following document is an extract from BS2754 - the standard concerning construction of electrical apparatus. We are aware that the document is ambiguous and unhelpful in places and we are working towards a more useful departmental interpretation, which will be agreed with the safety office. Meanwhile you may find the following points helpful.

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All equipment constructed in the Physics School is “class 1”, i.e. properly earthed and not “double insulated”. This considerably simplifies the interpretation of BS2754 – you can ignore regulations relating to “class 2”.

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Class 1 equipment stipulates that “The distance between mains voltage carrying parts and touchable parts must be at least 3 mm.” This should be interpreted as the air gap or “creep” distance around insulation. It does not prohibit smaller gaps where the insulation is continuous (as in an insulated cable).

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All mains equipment should be fitted with an IEC “plug in” mains connector. This further simplifies the interpretation of the rules on mounting and securing earth and mains leads.

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Equipment operating at less than 24 V DC is not a major concern, but sound constructional practices should be employed.

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You may consider construction of equipment which is powered by