RCD Tripping intermittently

[cliffed]

Called out to fault on RCD tripping maybe twice in a month for sometime.
Did all the tests & found RCD was faulty, Refitted a new Rcd Type A which made matters worst.
So refitted original RCD Type AC for the time being.
Insulation Resistance measurements were 20 M ohms.
Ring continuity fine too.
Testing proved difficult because of RCD tripping even with my Socket Tester, then everything went back to normal, power back on & days later still on.
Obviously Client not happy & believe’s ive done something.
The DB is a Stack DB,Crabtree Starbreaker all cabling brand new.
Its Split between Top & Bottom Main Switch mcb’s
Bottom RCD 30ma 80amp supplying 5 Ring Mains & 3 other Radial circuits MCB’s
i think I narrowered it down to-the kitchen/dining RM & UNPLUGGED all equipment but doing this the RCD still tripped.
Fingers crossed no call outs over Xmas… returning after hols … Any ideas fellow Sparkies

 

[suffolkspark]

How did you ascertain that the original rcd was faulty? Did you test the original rcd with outgoing circuits disconnected? If you havnt got an earth leakage clamp meter you can connect one circuit back at a time and use ramp test on your mft with no circuits connected, note the ma, then add back one at a time to see when its requiring less ma to trip, could point you in the right direction

 

[cliffed]

Yea all out circuits were disconnected & Rcd ramped tested
Think this will be the right way forward,with EL clamp meter
Cheers have a nice Christmas