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Low insulation resistance on remote hager rcbo board and effect on upstream devices.

hertzal123

Was asked to fit an extra skt to kitchen.Old 3036 cu so fit an enclosure with 40A rcd at side of cu.

Had tested IR of ring final earlier and found to be 0.03M.The low reading was traced to a detatched

garage with a 6way hager board spurred off the ring,comprising 6no rcbos with earth leads.The "fault"

as expected cleared when the leads were disconnected.My question is:had there been a greater number

of rcbos in the board or boards, so a lower ir,would the upstream 30ma rcd trip?

Thanks for any replies.

                                                   Hz

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    Well a 30mA trip could pop out at 15mA and just meet spec. Having tested a few 20mA to 25mA is more common.  In any case losing 10mA of the headroom you need makes for an unreliable system. (Put another way if the clamp meter on L&N reads 10mA or more on a 30mA RCD, then in my head I mark the circuit as possibly trippy, take extra care and do not add to it.)
    Mike

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    Well a 30mA trip could pop out at 15mA and just meet spec. Having tested a few 20mA to 25mA is more common.  In any case losing 10mA of the headroom you need makes for an unreliable system. (Put another way if the clamp meter on L&N reads 10mA or more on a 30mA RCD, then in my head I mark the circuit as possibly trippy, take extra care and do not add to it.)
    Mike

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