Rcbo tripping

[Sonia Norman]

I came across something new today. When I removed the main earth to do ze the rcbo tripped. Put the earth back in and it's fine. Can anyone explain what is going on?

 

[SparkyChick]

Without being there and being able to test and inspect, I can't say why it happened, but what I can say is you most definitely should not be removing the main earth with the power on.

 

[Dustydazzler]

Neutral current on the earth bar creating an imbalance ?

 

[James]

Without being there and being able to test and inspect, I can't say why it happened, but what I can say is you most definitely should not be removing the main earth with the power on.

Just to add a little to @SparkyChick

if you remove the main earth cable whilst the board is energised, it is possible under some circumstances (not unlikley) that the earth bar and any earthed metal fittings in the property become LIVE at any voltage up to the incoming phase voltage.

it puts a black mark on your reputation if the homeowner drops dead in the shower because you have removed the earth cable, and I expect the paperwork would be a nightmare.

 

[telectrix]

at least it would be a clean death.

 

[Vortigern]

As a matter of interest what type of RCBO is it. One with or without a functional earth two wire or one wire?. You get various variants with two wire, one wire which one is yours? We do not know if the board was energised at the time.

 

[pc1966]

1) Very bad practice to disconnect the main earth without isolating the supply
2) As @Vortigern asks, it might be a RCBO with a "functional" earth for this sort if fault (I think it is really for open N, but hey-ho, both lead to N-E volts).
3) There may be dodgy insulation somewhere and allowing the CPCs to float was enough to cause leakage somewhere.

 

[Vortigern]

Just for the record I think we must assume that if the OP knows how to do ZE it would be fair to assume it is also known to isolate the supply.

 

[stevethesparks]

I came across something new today. When I removed the main earth to do ze the rcbo tripped. Put the earth back in and it's fine. Can anyone explain what is going on?

So you are disconnecting the main earth whilst the board is still energised and circuits are switched on?
Unbelievable!

 

[telectrix]

So you are disconnecting the main earth whilst the board is still energised and circuits are switched on?
Unbelievable!

one life. live it. where's the fun in safe?

 

[James]

@Vortigern has made a very valid point

nowhere in the original post did it say that the main isolator was still energised.

both myself and others have in our own minds assumed that it is energised because the fault described would in most circumstances require the power to be on for it to manifest itself.

@Sonia Norman
if indeed you are testing Ze with the main isolator switched on, I hope you have learnt something from the posts.

if in fact the main isolator was off then there is something unusual going on there, possibly to do with a current flow between N and earth via the rcbo fly lead .

@ everyone else, remember that we are all human and don’t get everything right all the time.
I am sure if we look back at our own mistakes and failures, the odd one will make us cringe.

I for one can look back at a couple of events that didn’t go horribly wrong, more due to good fortune than perfect methodical working practices.

 

[pc1966]

nowhere in the original post did it say that the main isolator was still energised.

both myself and others have in our own minds assumed that it is energised because the fault described would in most circumstances require the power to be on for it to manifest itself.

Very true, I had made the assumption it was still energised. There might have been something else allowing the RCBO to trip even though the main power was isolated, though in itself that is worrying!

 

[stevethesparks]

It wasn't made clear either way, but generally mcb's / rcbo's are switched off before the main switch - or at least should be.

 

[Sonia Norman]

@Vortigern has made a very valid point

nowhere in the original post did it say that the main isolator was still energised.

both myself and others have in our own minds assumed that it is energised because the fault described would in most circumstances require the power to be on for it to manifest itself.

@Sonia Norman
if indeed you are testing Ze with the main isolator switched on, I hope you have learnt something from the posts.

if in fact the main isolator was off then there is something unusual going on there, possibly to do with a current flow between N and earth via the rcbo fly lead .

@ everyone else, remember that we are all human and don’t get everything right all the time.
I am sure if we look back at our own mistakes and failures, the odd one will make us cringe.

I for one can look back at a couple of events that didn’t go horribly wrong, more due to good fortune than perfect methodical working practices.

 

[Sonia Norman]

I have to admit it was live. A big learning curve.

 

[DPG]

I have to admit it was live. A big learning curve.

Full marks for owning up.

 

[SparkyChick]

I have to admit it was live. A big learning curve.

As James said, we all make mistakes.... the important thing is no one was hurt.