RCBO keeps tripping out to outbuildings

[Harry Bloomfield]

Checking to ground might be difficult as the ends of the cable are not near any exposed ground so I'll need a very long test lead, which i've not got to hand.

The ground is well, er - The ground, that everything sits on. Just insert a bit of metal rod into the soil.

What sort of cable is it?

 

[flameport]

just bridging the plastic tanks and bath etc. and join all the copper back to the main earth point my the meter

Absolutely not.
That is likely to make a safe situation worse.

and the cable is sitting in water somewhere in the duct creating the short.

Not impossible but very unlikely.
Most faults are at junctions / connections.

 

[EFLImpudence]

thats what i thought just bridging the plastic tanks and bath etc. and join all the copper back to the main earth point my the meter

Parts need bonding if and because they are earthed.

 

[jamesBen80]

In example 4 if a stray live conductor touched the isolated copper pipe it would raise it to mains voltage but would not trip any safety devices as there is no path back to ground (its isolated). If you then touched the copper pipe/tap while standing on a wet floor for example you would receive a shock? Although a safety device should detect it in time to isolate and prevent serious injury. This was why all exposed metal pipework taps etc was bonded back to the main earth block and to ground.

 

[EFLImpudence]

That is not the purpose of bonding.

That is earthing and your example shows why we do not earth cutlery.


What about when you contact that live conductor while touching a metal part; would you prefer that metal part be earthed or not?

That is why only parts which are already unavoidably earthed are bonded.

 

[flameport]

This was why all exposed metal pipework taps etc was bonded back to the main earth block and to ground.

Extraneous conductive parts are bonded, which are conductive items that can introduce a potential.
Typical examples are metal water pipes, metal gas pipes and metal framed buildings, as they are both conductive and due to being partially buried underground will introduce earth potential into the location.

Other random items of metal such as pipes wholly within a building, window frames, door handles, radiators and baths cannot introduce any potential from elsewhere as they are contained within the building or location.