mk rcd tripping

[Darren-Sparky]

hi, today i installed a 8 way mk rcd i had from left to right;

100a main switch
63a rcd

40a mcb cooker
32a mcb ring main
16a mcb immersion
6a lighting up
6a lighting down

tns system, i did my tests before i installed new consumer unit and all was good, when i tried to turn on cu the rcd would trip immediately, but other times i could turn on the cu and rcd would stay on but as soon as i plugged anything in to a socket or switched a light on the rcd tripped? also the test button would not operate i replaced the rcd with 3 new ones just incase and all the same results an intermittent fault that never really occurred more than once.

ive checked polarity of incoming tails and all seems good, i also couldnt get rcds to trip using my rcd tester,

any help would be appreciated

thanks

 

[Carlosfandango]

I foresee a neutral earth fault??

 

[Leesparkykent]

IR readings all good on every circuit?

 

[Darren-Sparky]

hi yes my thoughts exactly but, using a spare mcb i isolated all other circuits and run 1meter of 2.5mm twin and earth to a temporary socket and plugged my battery charger in and as soon as i switched on the rcd trips instantly,

 

[Darren-Sparky]

ir readings all good

 

[Carlosfandango]

But did you disconnect all other neutrals?

 

[Darren-Sparky]

i honestly think some how im getting a fault down the incoming neutral,

 

[Darren-Sparky]

no i left neutrals connected, but with all mcbs off the rcd stays on,

i then turn mcbs on one at a time and the rcb stays on

as soon as there is any load on any circuit the rcd trips

ive been racking my brains about this for hours thanks for your replys hopefully we can get to the bottom of this

 

[Leesparkykent]

Configuration of the board is wrong or neutral earth fault IMO

 

[Darren-Sparky]

configuration of the board? please elaborate

 

[trev]

Think about it Darren, why would the RCD hold until there's a load?
It's N-E. It has to be.
I'm really not sure why you did that thing with the 2.5 and socket. What were you hoping to achieve by that?
Get your tester back out and hunt it down because it's there somewhere mate

 

[Glenn Knights]

The only time I've encountered anything like this, it was traced to a nicked neutral on the load side of a switch fused spur - as soon as a load was introduced via the spur, it popped the RCD.

 

[Leesparkykent]

If you are 100% sure your IR results are good and the configuration of the board is correct, isolate 1 circuit at a time and diss the neutrals for the isolated circuit and repeat until you find the offending circuit.

 

[Leesparkykent]

configuration of the board? please elaborate

neutrals to corresponding neutral bars, etc

 

[Darren-Sparky]

the reason i did the temp socket was to try to establish weather the rcd would trip on a circuit i knew was wired correctly and it did