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EICR and IR Testing

Former Community Member
Former Community Member
Oh the bane of IR testing on EICRs

Now its just impracticle to disconnect all loads to carry out IR testing, I think everyone can agree on that. And that Phase and Neutral are connected then tested to earth.


This is what I do, and then test @250V as to avoid damaging any equipment in the installation. And unless the IR value was <.5 Meg, would not bother me. What BS7671 states, but BS7671 is maybe somewhat unclear in that if that voltage (250V) was used then .5meg value should used, but that value should only be used on SELV, and PELV. Now experience also tells me that even if you had a return 0.0, and then did Kohms by using the ohms setting, even values of 100Kohms are fine. (Actually can be much lower than this) and we are pretty clear that its not the cable reurning these values.


So question is when doing an EICR @ 250V, at what point would you recommend an FI? For me the value would have to be <.5Meg
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  • 0
    Michael Moore:

    Oh thats easy its 7.666Kohm

    0.008Megohm


    Which is what I alluded to on a Facebook group, and it completely baffled the bafoons there, who were apparently teachers!


     


    Ah, but.. RCDs can validly trip at a residual current of anything between 50% and 100% of IΔn so you should really be looking at keeping leakage below 15mA rather than 30mA for reliability (so perhaps 15.3kΩ rather than 7.6)


    There again d.c. insulation tests only indicate simple resistance - in a real system they'll be some capacitive coupling that'll allow some extra residual current to flow too (so perhaps something significantly higher than 15.3kΩ)


    Also there'll likely be leakage from appliances which likely won't be part of a fixed wiring test (even if they many appliances will have components switched off - e.g. pumps and motors of washing machines so likely to avoid the test) - so again you might want to add a significant margin on for that too..


       - Andy.


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  • 0
    Michael Moore:

    Oh thats easy its 7.666Kohm

    0.008Megohm


    Which is what I alluded to on a Facebook group, and it completely baffled the bafoons there, who were apparently teachers!


     


    Ah, but.. RCDs can validly trip at a residual current of anything between 50% and 100% of IΔn so you should really be looking at keeping leakage below 15mA rather than 30mA for reliability (so perhaps 15.3kΩ rather than 7.6)


    There again d.c. insulation tests only indicate simple resistance - in a real system they'll be some capacitive coupling that'll allow some extra residual current to flow too (so perhaps something significantly higher than 15.3kΩ)


    Also there'll likely be leakage from appliances which likely won't be part of a fixed wiring test (even if they many appliances will have components switched off - e.g. pumps and motors of washing machines so likely to avoid the test) - so again you might want to add a significant margin on for that too..


       - Andy.


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