UK RCD keep tripping.

[Kisssecurity]

Hi All..
I have a 16mm 3 core swa feed a 9way split board in shed, 30m from incomer .. from the split board I have run a 10mm 3 core swa to 2 way board for hot tub. This has a 63amp rcd in it.. the other end at the split board is also a 63amp rcd on its own of one side of the split board.. this keeps tripping. The other side of the split board is on its own 63amp rcd and feed mcb for lights and sockets in shed. The hot tub is 3kw max . No cable faults or overload..Why does my rcd at split board keep tripping every few days? If fault was at Hottub would the 2way board rcd not trip? Should I ditch the split board RCD and swap with just a 40amp mcb? Thanks All

 

[James]

This could turn out to be a N to earth fault somewhere.
Possibly water ingress into something.

 

[littlespark]

2 rcd’s on the same line is not ideal. Can you remove one of them?

Both are 30mA, which means they’ll trip before the fault current reaches that threshold. so it’s the most sensitive of the 2 which is tripping, not the one closest to the tub.

Maybe the other rcd is faulty. Has it been tested with the test button?