Thank you Andy I tested the rcd with the circuit breakers off

As Mike mentioned, that would leave the downstream N and PE connected - so a N-PE fault still seems like the most likely explanation. An insulation test (at 250V if you like) under the same conditions of things being plugged in/switched on as during your RCD test, but with the RCD off of course, will likely show the problem.

The current earthing arrangement shouldn't have any detrimental effect on the test - for a 30mA test it would only raise the touch voltage by around 6V - and just over 30V for a 5x test - both well within the 50V limit most testers accept.

   - Andy.

the other thing im not understanding is i set my metrel to 30mA type A rcd and it goes through the test's it comes back o.oo on all 4 test's but if i change it to type Ac i get trip times . this is the for the right hand rcd 

Thank you for all the advice from you all 

Does the RCD physically trip?

Yes ,I also changed the rcd to one i had in the van that did the same ,im going back tomorrow and go over the installation again .

Paul Berryman said:

Yes ,I also changed the rcd to one i had in the van that did the same ,im going back tomorrow and go over the installation again .

Again, is this test method 1, or 2, or both?

Paul Berryman said:

Yes ,I also changed the rcd to one i had in the van that did the same ,im going back tomorrow and go over the installation again .

Again, is this test method 1, or 2, or both?