Discuss RCBO tripping advice. in the Electrical Forum area at ElectriciansForums.net

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Evening All...I've not posted in a while which is a good thing as I can now work most things out myself!!

Just a bit of help needed with this one though!!

I have two consumer units, both have a mixture of MCB's and RCBO's on one of the consumer units the RCBO's are tripping randomly (The customer is adamant that it's since the smart meter was installed but probably coincidence),

I have done an IR test on the circuits with the RCBO's and they all pass. I didn't have time to test all the other circuits today but will do next time.

My question really is..would a N to E fault on the non-RCD circuits cause the RCBO to trip?

I'm just wanting a bit of info to go back with tomorrow as they customers are OAP's and they have had sparks look at it the past and not sorted it.

Cheere
 

James

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A N to E fault could cause the issues you are having.
it is the most likely fault unless of course the smart meter is within a foot (300mm) of the distribution board and then all bets are off!
 

timhoward

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My question really is..would a N to E fault on the non-RCD circuits cause the RCBO to trip?
No. An RCBO should only trip if there is leakage downstream of it on that circuit.
Remember the N bar is upstream from the RCBO. The circuits return N current path has to pass through the RCBO first , so the RCBO will be balanced, and won't notice any upstream N-E fault.

So circuits not on RCBOs with N-E faults should not normally affect RCBOs.
If upstream N-E faults tripped RCBO's then if you think about it every TNCS setup would have a problem.

In this case I'd quickly test the other circuits, and then believe the customer, as smart meters can most certainly cause this problem.
What make CU is it?
 

marconi

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A thought. Do the RCBOs have a functional earth? Some RCBOs use the FE to monitor N-E voltage and if it rises above a threshold they trip because it 'thinks' the supply side N has become open circuit. Check then the goodness of up stream N and E conductor connections and indeed the functional earth connections. This could tie in with the client's observation about it all starting after the smart meter was installed.
 
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No. An RCBO should only trip if there is leakage downstream of it on that circuit.
Remember the N bar is upstream from the RCBO. The circuits return N current path has to pass through the RCBO first , so the RCBO will be balanced, and won't notice any upstream N-E fault.

So circuits not on RCBOs with N-E faults should not normally affect RCBOs.
If upstream N-E faults tripped RCBO's then if you think about it every TNCS setup would have a problem.

In this case I'd quickly test the other circuits, and then believe the customer, as smart meters can most certainly cause this problem.
What make CU is it?
Hi thanks for the advice, it's a Hager CU.
 

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