RCD tripping on "No Trip" Zs test

[Geoffers]

Hi folks,

changed a CU over yesterday to a dual RCD board. Standard affair, all tests fine. Did live tests, started doing the Zs for the lights. Both up and downstairs lights kept tripping the RCDs. I'm using my Megger with the 3 leads to avoid tripping. Megger was set to No Trip Loop and all that. Zs for all other circuits fine

Am i missing something? .......cpc's are all present and correct in all circuits as i thought initially i may not be getting a good earth.

Stumped

 

[telectrix]

are the 2 lighting circuits on the same RCD, or 1` on each? is there the possibility of there being some leakage existing, so that the Zs test current takes it over the threshold? do a ramp test on the RCDs.

 

[SPARTYKUS]

Where you based geoffers

 

[Guest123]

Did you try testing the RCD's to establish if they are goosed or not???

Unlikely but needs ruling out at least.

 

[Geoffers]

are the 2 lighting circuits on the same RCD, or 1` on each? is there the possibility of there being some leakage existing, so that the Zs test current takes it over the threshold? do a ramp test on the RCDs.

lighting circuits are on different RCD's ....good idea re ramp test

 

[Geoffers]

Where you based geoffers

im in north london but job is in ickenham, middlesex

 

[Geoffers]

Did you try testing the RCD's to establish if they are goosed or not???

Unlikely but needs ruling out at least.

yeah, good point but as all other circuits tested fine i ruled this out, bit hasty perhaps....

i'll go back and approach with a fault finding head on ....

thanks all!!