help with ring circuit

[Zehroni]

I have rewired the whole of my house after new extension. And so far I managed to do the extension 2 ring power circuits, the kitchen and the main house upstairs circuit without any issues and all are working and connected to individual RCDs. however when I connected the main house power ring circuit, the RCD trips. I disconnected the first and the last sockets where the wires go to the CU and the the RCD trips still trips. I then connected them to the old breaker without the the RCD and still trips. where I am going wrong? the short wires are visible to me and visual inspection does not show any damage to them. where I am going wrong? help please

 

[EFLImpudence]

I have rewired the whole of my house after new extension. And so far I managed to do the extension 2 ring power circuits, the kitchen and the main house upstairs circuit without any issues and all are working and connected to individual RCDs.

Do you mean RCBOs?

however when I connected the main house power ring circuit, the RCD trips.

Again, do you mean the RCBO?

I disconnected the first and the last sockets where the wires go to the CU and the the RCD trips still trips. I then connected them to the old breaker without the the RCD and still trips.

It would appear you do mean RCBO and it is the Overload part that is tripping.
Therefore you must have a Short Circuit (L-N) or Earth Fault (L-E) somewhere along the cables.

 

[Zehroni]

thanks for the speedy reply. yes I meant RCBO. yes but i can not see where the Short Circuit is. both ends and the wire are visible to me.

 

[EFLImpudence]

That is why we test before switching on the power.

Do you have a multimeter?

 

[Zehroni]

yes I do

 

[Zehroni]

I did test the résistance of the 6 wires, the 2 blue and the brown and the earth of the full circuit. the the reading I got is 0.9 for L and 0.9 for N and 1.1 for earth

 

[OwainDIYer]

Now test the resistance of L to N, and
(L and N joined together) to Earth.

 

[Zehroni]

do you mean L from one wire to N for the other wire and vise versa? and again the earth to each of them?

 

[EFLImpudence]

It would be better if you tested between L & N then L & E in one of the cables.

Bear in mind that the wires are connected in the CU so you will be testing both cables at once.

If there is a low resistance between either LN or LE, you will have to disconnect the wires in the CU and repeat the test on each cable to find which is the faulty one.

 

[Zehroni]

none of the wires are connected to the cu now I have them all out to inspect them. Hence I have 6 wires L,N, and E from one cable which I call the out and another 3 wires from the second cable which I call the return. I have now connected and the power socket back again.
for the out cable the resistance is L & N =0.9 and L& E =0.9
for the return L & N 1.4 and L&E 1.0 does this mean this is the faulty cable

 

[EFLImpudence]

No. Disconnect the cables from the socket and from the CU so you have this"

Test between L - N, L - E and N -E (not end to end) on both cables.

There should be no Ohms reading for any of the tests.

If you have an Ohms reading on one of them, then that is the faulty cable.

 

[BS3036]

There should be no Ohms reading for any of the tests.

Well, strictly speaking 'a high Ohms reading'.

 

[davelx]

Well, strictly speaking 'a high Ohms reading'.

{set /mode=pedant}
Well, strictly speaking, a high resistance reading, Ohms being the unit of electrical resistance or impedance. You don't say that someone has a high Centigrade reading, you say they have a high temperature.
{set /mode=nopedant}

 

[BS3036]

I was not trying to be pedantic - just to stop the OP interpreting no Ohms as zero Ohms.

 

[AndyPRK]

And if your doing it the bang way.

you don’t need to connect both ring cables to test. Just one. To see which one at fault. Just one set of LNE