John asks this question about whether it is necessary to complete an insulation resistance (IR) test on lighting circuits. It has been answered by the Electrical Contractors Association (Theme - Testing, Tools and Equipment):
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Question: Can you advise me what is best practice when insulation resistance testing an existing installation for maintenance purposes?
Is it necessary to complete an insulation resistance test on lighting circuits?
If ‘yes’, presumably this would means disconnecting every luminaire to avoid damage. This would be incredibly labour intensive, which is the reason for my question.
Answer: In an ideal world, all circuits would be tested fully and the results recorded on a, Electrical Installation Condition Report (EICR).
However, on large installations, the cost of doing a full test in this way would be prohibitive to most clients, which is why appropriate sampling is permitted.
If is not practical to carry out an IR test on part of the installation, however, this needs to be agreed with the person ordering the work - and should be recorded as a limitation on the report.
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