head banging... help needed!!

[Top-Spark]

Hi all, changed a db today and hay presto... Goodbye RCD!! been testing all day and still can't find the fault!! when I turn any light switch on the RCD trips but only if under load!! Remove the lamps, it doesn't trip!! both light circuits are currently on same RCD aswell!!

 

[telectrix]

neutral earth reversal on the circuit?????

 

[Billynm]

Youv'e got the neutrals on the "right" side ??

 

[Darkwood]

Physically disconnect the circuit L/N/E and insulation test the circuit then try insulation testing each core to the N bar of the non rcd side .... a crushed cable to a non rcd circuit can give similar symptoms .... i had it when ever load was plugged into the sockets on a 16th board it was traced to a crushed cable on the non-rcd lighting leaking to socket N.

 

[Top-Spark]

Cheers, iv got correct polarity at all fittings but know there's at least 2 joints under the boards upstairs! Not wrong bar as temp got both lighting circuits on same RCD!! small problem I have is I'm going to Spain tomorrow evening so got about 4 hours onit in the morning!! :-/

 

[Octopus]

Did your testing not indicate any issues?

 

[Top-Spark]

Yes... RCD won't trip under test (>35MA) that's the same testing from the db.... But took 2 back today as they have all done that so on the 3rd RCD now but that's doing the same! Pulling my hair out...

 

[SirKit Breaker]

Hi all, changed a db today and hay presto... Goodbye RCD!! been testing all day and still can't find the fault!! when I turn any light switch on the RCD trips but only if under load!! Remove the lamps, it doesn't trip!! both light circuits are currently on same RCD aswell!!

Sounds like you need to be methodical in your testing.
The RCD will only trip if the lamps are in place, it wont if they aren't cos your switches are in the line conductor only, it is your load that connects across Line and Neutral.

Start at the beginning with your testing, it will be quicker than clutching at straws, and my best guess is that doing continuity, then IR will sort this out in no time.

Cheers...............Howard

PS just a thought, is there any sign of a light being added somewhere DIY fashion, and the DIY'er due to a lack a neutral, has tapped into the nearest circuit available? Sockets!

 

[Octopus]

Yes... RCD won't trip under test (>35MA) that's the same testing from the db.... But took 2 back today as they have all done that so on the 3rd RCD now but that's doing the same! Pulling my hair out...

Now you've confused me completely.

What make of CU/RCD is it?

 

[Silly Sausage]

Where's MDJ?
There might a cheap ticket to Spain going spare! :smilielol5:

 

[Top-Spark]

Iv allready removed a single core yellow1.5 this morning that was buried in the wall connecting the outside light to garage socket!! That was the 1st fault... It's a wilts plus (control gear) db! Generally good CUs!!

 

[Richard Burns]

I would say that you have a connection between the two neutral bars.
This would explain the non tripping on test and only tripping under load.
The problem is finding the link, that is where the continuity tests between neutrals will identify the issue, start with just between the neutral bars and remove neutrals until it stops being continuous. Then test from that last neutral to the other neutral bar and then vice versa for the other neutral bar; then you will have the two connected circuits (unless the two neutral bars still have the link in in the CU) to check out if the field.

 

[telectrix]

almost deffo a N-E fault of some sort. had it before where rcd WON'T TRIP UNDER TEST, BUT TRIPS ON LOAD.

 

[stuartcourt]

test each circuit one by one, as said it sounds like you are getting ****ed when a clear head is needed at all times.

 

[Top-Spark]

Yea... I'm defo over-thinking!! Hence posing on here, sometimes you over look the simple things! Thanks all for your help, I'll post tomorrow with results (if I can find the post!! ) thanks again!

 

[telectrix]

be fair, glenn, it sounds like an awkward fault that didn't show up before the CU change. could be something glaringly simple, but he's having a blonde one.

 

[kingeri]

A tad harsh there Glenn..............

 

[GLENNSPARK]

well for a start if its only doing it when loads are connected then this suggests a neutral-earth fault...
further more if its when he turns on any light.....this suggests something near the board...

 

[Octopus]

Wonder what the Zs is for the circuits he's tested?

 

[HandySparks]

...further more if its when he turns on any light.....this suggests something near the board...

Why?
..

 

[Top-Spark]

Y can't i see Glenn's comments?! :-/

Tel, no didn't show up on Pre testing!! Now I'm in it!! Lol!

 

[GLENNSPARK]

Why?
..

yeah...point taken..
i am not in thinking mode tonite..
just in a bad mood...

 

[onions1066]

When your testing your rcd are you doing it with your 3 leads at the board or at a socket?

 

[Top-Spark]

Murdoch - pme, 0.78 (if memory serves me) !! Good reading... That's not the 'end of' the circuit though (there isn't one) must be under floor in jb for a wall light.... Somewhere!!

 

[Top-Spark]

Onions... Sockets on other RCD, for this RCD currently controlling up and down lights (2sep circuits but temp on same RCD) have tested at 4 points -one upstairs, 2 down, and at mains and none are tripping <35mA!!