Rcd trips before I even switch on MCBs

[oldstudent]

Hi all

I've just fitted a new consumer unit. 10 way twin RCD.

After a very long day struggling in a tight location I powered up.

Switched on RCD furthest from isolator, held in OK, switched on mcbs protected by that RCD all OK

Switched on RCD next to isolator wont stay in. Even with no mcbs switched on.

Thought it may be a faulty RCD so swapped them over, same problem.

With no mcbs switched on either side, Rcd still wont hold in next to isolator.

I'm too tired to carry on now, can anyone give me some suggestions where to start checking in the morning.

Pre instalation tests were all fine

TNS system.

Only thing I had to do was extend some cables within the enclosure using crimps.

Thanks

 

[Knobhead]

If it was a shared neutral between the two RCD’s it would be a ---- up as to which tripped first. You swapped the RCD’s and the fault stays with the same side.
Look for a neutral / earth fault.

 

[Amp David]

OP suggests he has already completed his tests, so in theory if all complete and ok shouldn't be anything to do with the install.

 

[telectrix]

could he have a hi integrity board and has used the non protected N bar? maker's tails incorrect? does sound like the fault is in the board.

 

[tony mc]

Any update as to the fault ??????

Quite a few responces to your post!!!!

 

[telectrix]

perhaps it was such a stupid thing, he's keeping his head down

 

[johnthesparky]

first dual split load wylex I did (should I post this on a forum)

had no non-RCD protected circuits, so wired first RCD to neutral bar one, and second to bar two and left bar 3 empty (hope that makes some sense to someone).... and guess what

it was a roasting day, the guy was a DIYer and had made all sorts of improvements, I was just going to the van for a cry when I had my eureka moment...

so yeah.... ^^^ what they said neutral earth fault, or cross coupled neutral

 

[nickblake]

nice one good to here you found the fault , the more you see then the more they become like riding a bike and you ll be saying oh not again and delve into sockets/ lights searching for the fault

 

[RWJ]

(easy peasy a cu change,....anyone can do that cant they?)

YES!!!! They come with instructions!!!!
View attachment 6371

Well the ones from wickes do!!! "Fitting and installation instructions included"




Glad you found the fault, and fixed it with out too much hassle!!!!

 

[greenspark]

Is there a borrowed Neutral on the landing light? Sometimes the landing light at the top of the stairs is part of the downstairs light circuit (or Vice Versa) but some lazy sod nicks a neutral over from one of the upstairs ceiling roses. Has that been mentioned?

 

[nickblake]

Is there a borrowed Neutral on the landing light? Sometimes the landing light at the top of the stairs is part of the downstairs light circuit (or Vice Versa) but some lazy sod nicks a neutral over from one of the upstairs ceiling roses. Has that been mentioned?

Na not lazy thats was a common wiring method during the 60's and 70's

 

[Knobhead]

Na not lazy thats was a common wiring method during the 60's and 70's

1950's more like in POSH houses.