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LlandrilloSpark

Can someone offer a solution to this RCD trip?
I've been doing some work at my sister's 112 year old house, it started with me installing a split load board but soon became obvious that the wiring wasn't up to scratch anywhere in the house, I.e two core feeding socket outlets no cpc!
The kitchen extension has it's own ccu with two 15A and one 5A rewirable for power and lights, this is fed via a 10mm t&e with contactum 32A breaker on the rcd side, id say the cable is a good 40 years old, the day after installation the rcd tripped, the kitchen supply was the only circuit on it at the time.
Due to a new kitchen being fitted, i now have been asked to rewire the whole kitchen, I have fitted a new proteus 4 way with rcd main switch, one 6A lighting circuit and two power, the cooker is still on the old board.
When I switched on the mcb in the main board the new rcd main switch tripped straight away, this was without the cable under any loading and all the mcb's in the new ccu switched off.
I have tried the following, I disconnected the bus bar and it still tripped, I but the neutral tail straight into the bar and it held untill I switched on any of the 3 circuits then it popped, I even bypassed the whole rcd putting the neutral tail in the bar and the line into the mcb's, the circuits worked fine and I got good Zs on the sockets, the pre commision tests came back fine on the new kitchen , all insulation resistance over 550 meg ohm.
Can the RCD pick up something down stream?, is it the supply cable?, i was thinking about bringing a new 4mm earth from the met to the new ccu, also should I dissconnect the new circuit neutrals one by one and c if I can pinpoint that way. Or is it back to the main switch and stuff the rcd.*
Help appriciated
Lighting in utility has a small fluerescant fitting on it
Cheers
 
Can the RCD pick up something down stream?, is it the supply cable?, i was thinking about bringing a new 4mm earth from the met to the new ccu, also should I dissconnect the new circuit neutrals one by one and c if I can pinpoint that way. Or is it back to the main switch and stuff the rcd.*
Help appriciated
Lighting in utility has a small fluerescant fitting on it
Cheers

The RCD won't pick up any fault before it. Like you've suggested, disconnect the neutrals one by one and narrow it down that way. If you know there''s a fault, why would you do away with the RCD?:confused:

Edit: Thinking about it, there might me some current on the N? Have you got a clamp meter?
 
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Get the tester out and IR test each circuit Lto E ,E to N, N to L, this should show where the fault is , i must admit i wouldnt had installed a RCD main switch as the sud board is so small i would have used RCBO's less inconvieniance if an RCBO trips , i see you have tested test again as what you have desrcibed indicates a fault i will put my money on a N to E fault
 
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I think what gets me is that it tripped with no load on kitchen and bus bar disconnected, so most prob a neutral to earth fault?, I can't even go back today at the moment as my missus is due imminent!
 
Can't quite visualise the set up from your original post - but ii would sustitute in a working rcd of some description to check the first one if you are still having problems, before wrecking your brain on a problem that might not exist.
Is your clamp meter an earth leakage one ie one that can read in milliamps?
 
i would agree with it being a N-E short somewhere, also did you try a ramp test on your rcd? i have had an 30ma rcd tripping at 11 ma before and the natural earth leakage kept tripping it.
 
Llandrillo spark take it your near Llandudno then , if this is the case send me a message and ill send you my mobile number , im based on anglesey , may well pop over if you get stuck, thinking about it if its a split board and your supplying the sub board from there you have connected the neutral of the sub board to the unprotected side of the split board and not the protected side
 
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Nick, yes mate in Llandudno, I'm going Sunday to have a look if I can't sort it I will get in touch, main board is not splitload, I had to change it back to just main switch as when I had the RCD in the kitchen sub supply cable which I'm still using to supply the newCCU in the kitchen tripped the RCD, but it could of also been the shoddy existing wiring in the kitchen, the supply cable is fault free, all my precom tests came back fault free also, I'm guessing i may of trapped a conductor when screwing light fitting or socketon to wall after testing?, I spent from 7.45am-10.05pm on Thursday so I didn't have time to fault find, like I say I'm going on Sunday if I can't sort it I will get in touch mate, thanks for your offer
 
If the kitchen C/U you installed is fed via 10mm t&e from the RCD side of the main board, why would you need an RCD main switch in your sub board?

Personally i would use a normal main switch in the sub board for the kitchen as the circuits already have RCD protection from the Main C/U. Obviously you would test the IR of the 10mm supplying the kitchen. In the kitchen sub board you have 2 x 16A and 1 x 6A?? If so I would put a 40A mcb in the main board to cover the kitchen sub board.
 
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Right when you go back on sunday , disconnect all the circuits then test each circuit one at a time if you join the l and n to gether and do a test to earth and see which circuit is causing the fault , once you find it then reconnect all the other circuits and then switch power on and see if the RCD trips if all ok then test the faulty circuit , with faults like this rather than do an IR test do a continuity test you are looking for high readings , if you get a reading then youve found your fault ,example now ,if say you get a continuity of 0.89 say N to earth ,if you have a plug type test lead then plug this into the socket and test at each socket the lower the reading the closer you are to the fault when you have the lowest reading remove that socket and look for a possible fault , if you remove the socket from the wall still connected and retest if its clear then the fault was a trapped conductor ,once you find your fault refix the socket again and retest if all clear then carry out a IR test to confirm all is well , hope this helps
 
From what you say if you have replaced the CU in the kitchen and the RCD is tripping when none of the MCBs are on then the only cause that can make the RCd to trip is a N-E fault but this should have been picked up when you carried out the testing for certification.
 
Totally agree Ian but it wasn't!, all came back >550 Meg Ohm on IR tests, like I said to nick I may have trapped something when putting light fittings or sockets back on
 
Plus, a simple IR test between circuit N conductors to make sure you have nothing borrowed.

Also, did you do an ir Test between N & E?
 
It's a proteus 4 way, the outgoing N from the RCD is a solid copper hook type bar, neutral tail into N on the top of RCD and the hook going the the N bar in the ccu
 

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