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Minimum IR values

OCB99

Hi everyone, 

First time poster so try and take it easy on me Grin

been looking at threads on this forum for quite a while now and it’s been a great help during my training so thanks everyone.

Just wanted to know your opinions on IR testing and how to apply the minimum value stated in BS7671. The regs state that the values in table 64 applies to a distribution circuit with all final circuits connected. Would that mean if on an EICR for example there were 10 circuits each measuring 9Mohms between two conductors (Very unlikely I know) it would be a fail as the total resistance for 10 circuit would be theoretically 0.9Mohm?

Also would this apply to simple installations where the consumer unit is directly connected to the origin, essentially classing the DNO cable as a ‘distribution circuit’.

Thanks in advance.

Parents

  • Yes the converse is important to remember, not only is the test definition necessarily very wishy washy, its usefulness is not always clear - not all faults show on an IR tester at any detectable level. The classic being the live nail problem, so long as the wall is dry and the nail only hits the live core then it may well not fail an IR test on inspection. This does not make it safe !!

    It does find dead shorts OK but then so would a battery and bell set.

    Far more important is an earth continuity test of some kind, either R2 and wander lead or R1 +R2

    Mike.

Reply

  • Yes the converse is important to remember, not only is the test definition necessarily very wishy washy, its usefulness is not always clear - not all faults show on an IR tester at any detectable level. The classic being the live nail problem, so long as the wall is dry and the nail only hits the live core then it may well not fail an IR test on inspection. This does not make it safe !!

    It does find dead shorts OK but then so would a battery and bell set.

    Far more important is an earth continuity test of some kind, either R2 and wander lead or R1 +R2

    Mike.

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