RCBO problems

[WDMDL]

If the RCBOs are tripping, there is an imbalance somewhere. It's not looking like a fault to earth, so is it an interconnection (Borrowed Neutral)?
Try this one:
Safely isolate the supply.
Disconnect the (now 2 radials) L and N from CU and bunch the lot together. Connect to one side of tester
Link L and N busbars in CU. Connect to other side of tester.
Test first on a continuity range. If it shows no connection, test at 250V.

While 4Meg is acceptable, and in theory it would take something as low as 7.67kOhms to trip the RCD, it is pretty low for a small domestic and will be worth investigating.
At this stage, it will be worth pulling every socket frontplate to inspect, if you haven't already. IR test as you go, both the cables and the socket outlets themselves.
Apart from the kitchen ring, do the other circuits have RCD protection?

Simon.

 

[telectrix]

does sound a bit like a neutral/cpc crossed somewhere.

 

[BLBelfast]

If the RCBOs are tripping, there is an imbalance somewhere. It's not looking like a fault to earth, so is it an interconnection (Borrowed Neutral)?
Try this one:
Safely isolate the supply.
Disconnect the (now 2 radials) L and N from CU and bunch the lot together. Connect to one side of tester
Link L and N busbars in CU. Connect to other side of tester.
Test first on a continuity range. If it shows no connection, test at 250V.

While 4Meg is acceptable, and in theory it would take something as low as 7.67kOhms to trip the RCD, it is pretty low for a small domestic and will be worth investigating.
At this stage, it will be worth pulling every socket frontplate to inspect, if you haven't already. IR test as you go, both the cables and the socket outlets themselves.
Apart from the kitchen ring, do the other circuits have RCD protection?

Simon.

Thanks for your advice. I have taken every plate of and tested as I went. Thats what is killing me. I already spent hours investigating all I could think of.

The ring main, cooker, shower, kitchen ring are all RCBO protected. The lights and the rest are on the other side of the split board protected by RCD. I have tried sticking the circuits into an MCB on the RCD protected side and it still trips out the RCD.

The fact he has a few bits of computer equipment shouldnt affect the installation should it? Also the fact it got steadily worse has anybody got a bit of experiance with that sort of problem?

Thanks for everyones input. Will be back on friday for another hair pulling out session and will let youse know the outcome.

 

[LukeD]

I hate to say this.... But i love "Mystery Threads" like this !!!

may i make one suggestion ? Take a "fresh set of eyes" to have a look . some times you get into a mess with issues like this and some bugger comes along and "spots" it in seconds !

 

[nickblake]

It will be some thing stupid and you will kick yourself for not finding it , you said the 2 RCBO's tripped then as i know the guys have said it sounds like a crossed neutral or an inter connection between the ring legs , what i suggest is do an R1R2 test from the board joint the Earth and live to gether and test every socket on the ring , you should get a reading only on one leg as you have split them ,check both legs , then do the same but R2and Rn test all the sockets again you should only get reading on one leg , if you get reading on both legs then you know you have a crossed neutral , double check the IR readings too

 

[telectrix]

and another thought. check if there is any sort of continuity between one ring and another. it's within the realms of possibility that you have a neutral borrowed from one ring to another.

 

[chrisreid186]

i have the same kind of fault but with a rcd, even if i plug something into the ring with the mcb turned off it still trips the rcd, going back this weekend to have another look, i'm going to clamp meter the cpc to check for any high current there , let us know how you get on

 

[Octopus]

and another thought. check if there is any sort of continuity between one ring and another. it's within the realms of possibility that you have a neutral borrowed from one ring to another.

If you had a borrowed neutral wouldn't the "other" ring also be suseptible to tripping?

 

[antimatter]

Yeah definetly connected properly. These ones, type B have no functional earth.]


Yes they do.

Its to provide an electrical path when you press the test button. That's why its coloured cream and not green and yellow.

 

[IQ Electrical]

Yeah definetly connected properly. These ones, type B have no functional earth.]


Yes they do.

Its to provide an electrical path when you press the test button. That's why its coloured cream and not green and yellow.

I think you'll find the test button is purely mechanical, just releasing the latching mechanism.

 

[antimatter]

I think you'll find the test button is purely mechanical, just releasing the latching mechanism.

And your point is?

 

[IQ Electrical]

My point is that the test button creates an imbalance between line and neutral, through a resistor and checks mechanical operation only, it does not check or use any part of the earth system.

Pedantic yes but guys studying 2330, 2391 etc. need this level of accuracy.

 

[telectrix]

If you had a borrowed neutral wouldn't the "other" ring also be suseptible to tripping?

should think so, but stranger things have happened at sea.

 

[BLBelfast]

Yeah definetly connected properly. These ones, type B have no functional earth.]


Yes they do.

Its to provide an electrical path when you press the test button. That's why its coloured cream and not green and yellow.

No they dont . Some manufacturers do, some dont. this one controlgear or some other cheap ****e, dont.

 

[IQ Electrical]

The cream fly lead is to provide earth leakage protection under loss of supply neutral conditions.