Hi all, would like to pick your brains with this problem.
got called out to a tripping rcd. Separate rcd connected to 15yr old cu by mk.
the cu services the main house electrics in a quite frankly over-extended single phase system, consisting of 1 main incomer, split into 3 separate legs each with it's own cu and separate rcd's for stables and other outbuildings, all tt'd although it's not agricultural, just big...
Any way, the rcd for the house cu - 80A 30ma apparantly started tripping intermitently on 1 socket ring main. No recent work or changes done for at least 3 years at all. This intermittent tripping getting worse and now spread to second ring main. I get there to find a 10 way mk board with 3 light circuits, 5 32a circuits and a 16a garage door circuit. 3 of the five 32a circs serve ring mains but 2 have an extra radial live connection shoved into the mcb's. 1 32a is for the cooker, the other is shower-which is rarely used. When the 32a circs are energised the rcd trips on 2 of them immediatly(sockets). 1 has a straight ring, the other with the extra live. the other circs seem ok until i turn the cooker on which then trips the rcd making 3 faulty circs. removing the extra cable and leaving one leg out on the rings makes no difference.
Noticed on some of the cabing the green residue from that 60/70's cable that breaks down the insulation is part of the system but from what i've read that usually isnt an issue.
I've run the usual tests inc cont/IR/R1+R2/loop etc and found nothing really untoward except the main earth loop is a little high at 220 ohms.
swapped out the rcd with no change. this has got me frustrated as it doesnt make sense to have 3 circs out of 9 causing this that should be separate and dont throw odd readings. any ideas greatly appreciated
got called out to a tripping rcd. Separate rcd connected to 15yr old cu by mk.
the cu services the main house electrics in a quite frankly over-extended single phase system, consisting of 1 main incomer, split into 3 separate legs each with it's own cu and separate rcd's for stables and other outbuildings, all tt'd although it's not agricultural, just big...
Any way, the rcd for the house cu - 80A 30ma apparantly started tripping intermitently on 1 socket ring main. No recent work or changes done for at least 3 years at all. This intermittent tripping getting worse and now spread to second ring main. I get there to find a 10 way mk board with 3 light circuits, 5 32a circuits and a 16a garage door circuit. 3 of the five 32a circs serve ring mains but 2 have an extra radial live connection shoved into the mcb's. 1 32a is for the cooker, the other is shower-which is rarely used. When the 32a circs are energised the rcd trips on 2 of them immediatly(sockets). 1 has a straight ring, the other with the extra live. the other circs seem ok until i turn the cooker on which then trips the rcd making 3 faulty circs. removing the extra cable and leaving one leg out on the rings makes no difference.
Noticed on some of the cabing the green residue from that 60/70's cable that breaks down the insulation is part of the system but from what i've read that usually isnt an issue.
I've run the usual tests inc cont/IR/R1+R2/loop etc and found nothing really untoward except the main earth loop is a little high at 220 ohms.
swapped out the rcd with no change. this has got me frustrated as it doesnt make sense to have 3 circs out of 9 causing this that should be separate and dont throw odd readings. any ideas greatly appreciated