Crabtree RCD's

[Qedelec]

Your opinions would be welcomed for a little recent problem.

Fitted a new Crabtree split load CCU in the summer and ever since the customer has complained of nuisance tripping, but when ever I check all seems ok.
Last week I went out again (lucky they are across the road from me) and have built a box to introduce earth leakage from phase or neutral.
RCD will take 10mA but not 20mA, phase to earth (neutral to earth is fine).
The RCD will trip if:-
A light switch, not supplied by the RCD, arcs.
A MCB supplied by the RCD is switched on/off.
The RCD will also not reset with any load applied.
Proved the fault to the RCD by swapping with my own from my CCU and it will take 20mA without tripping.
Wholesaler supplied a replacement but this was worse, in that it would trip when all breakers were made.
RCD is 63A 30mA supplying 4 x 32A, shower and 3 A1 rings.

Has anyone else had similar problems with these RCD's or have I been very unlucky.
P.S. I got the wholesaler to replace the originally supplied RCD as it was not latching every time.

 

[JohnD]

When you say it trips at 20mA, do you mean in total, or added to the background leakage? There will usually be constant leakage esp from washing machine, immersion heater, garage circuits, and maybe it just takes a little extra to push it over the edge?

 

[Qedelec]

Good point John and a valid question.
I was concentrating on the fact that switching a supplied breaker will trip it.
I had most items isolated but cannot be certain all were.
It doesn't change the fact that out of 3 RCD's only one would accept the 20mA leakage.

 

[andy]

it should not trip at 20mA

 

[Spark123]

Have you got access to an RCD tester with ramp function? If so maybe worth isolating L & N load from RCD and see how many mA it trips at on its own.