Coding for low insulation resistance

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Question:

What code should I put on my EICR if the insulation resistance reading is low?

I have recently carried out an EICR at a church parish hall were one of the insulation resistance readings were found to be 0.53 Megaohms. The circuit was wired pre-17th edition. I'm of the opinion a code 3 would suffice (on further investigation) due to minimum accepted values at this time period being 0.5 Megaohms. Your thoughts and guidance would be greatly appreciated.

Answer:

NICEIC Technical Expert

An Electrical Installation Condition Report provides an assessment of the in-service condition of an electrical installation against the requirements of the edition of BS 7671 current at the time of the inspection, irrespective of the age of the installation.

In addition, the introduction to BS 7671 contains the statement that “existing installations that have been installed in accordance with earlier editions of the Regulations may not comply with this edition in every respect. This does not necessarily mean that they are unsafe for continued use or require upgrading”.

If you are considering a Classification Code C3, Improvement Recommended, as the measured value of Insulation Resistance is below the minimum values given in regulation 612.3.2 and is therefore not compliant with current regulations, we would also recommend a consideration of the effect that this low insulation resistance will have, to determine if it creates a safety issue to the users of the installation.

For example, if the low insulation resistance is between a live conductor and earth, could harmful fault currents flow in conductive parts which are accessible to the users of the installation? If you believe a potentially dangerous situation could result you may consider a Classification Code C2 as recommended in the Electrical Safety First’s, Best Practice Guide 4, Electrical Installation Condition Reporting.

We would also suggest comparing the measured value obtained with any previous Electrical Installation Condition Reports or Electrical Installation Certificates which provide evidence of the same circuit’s Insulation Resistance value.

This will enable you to determine the extent of deterioration with respect to the circuit’s Insulation Resistance, which could be considered when recommending the date of the next inspection and test or could result in the consideration of a Classification Code FI, Further Investigation Required if unexpected and concerning deterioration is identified.