I’ve disconnected the load (supply to RCD for shower) from the RCBO but as soon as I supply power by switching on the Main Circuit Breaker the RCBO trips. How to troubleshoot ? Has the RCBO died ? 

Start by disconnecting both wires (L and N) at the output side of the RCBO, if it still trips it's almost certainly busted.

 

Is this something that just started happening after working good for some time previously?  Anything changed coinciding with the tripping?  

44 minutes ago, Crossy said:

Start by disconnecting both wires (L and N) at the output side of the RCBO, if it still trips it's almost certainly busted.

 

Yes that’s what I meant by no load. 

 

Don’t know how long its been happening - its on a second shower that only gets used when we visit the family.

Check the "Test" button is not stuck, but I think it's time for a replacement.

If you have a sensitive clamp-on ammeter then clamp around the neutral and hot. Barring that or just replacing it, check voltage to ground on the neutral and hot at the heater. Reversed leads will often cause a trip. 

3 minutes ago, tjo o tjim said:

If you have a sensitive clamp-on ammeter then clamp around the neutral and hot. Barring that or just replacing it, check voltage to ground on the neutral and hot at the heater. Reversed leads will often cause a trip. 

 

Whilst this is generally good advice our OP has removed the outgoing cables from the RCBO (post #4) and it is still tripping.

A trolling post (and replies) has been removed.

 

It is a process of elimination. 

 

Last resort is to replace the breaker, NOT the first, due to the replacement cost. 

There are many reasons here for tripping.

Too much load (amps) from the shower.

Earth/water leakage from shower unit.

Internal electrical/fault with Shower.

Faulty RCBO, unlikely if not that old,

Gecko has shorted a circuit board.

 

The wiring in the roof is touching steel or other wiring. Thais tend to twist wires together and tape them, however, in my experiences in some cases I have seen where the sharp end of the wire becomes exposed and then has the capability of shorting out against steel or in my case a worker installing a tv cable got a shock on his foot, luckily my RCBO trigger with no major shock. 

 

Poor wiring (common in Thailand) Due to the back yard electricians here who have no formal training in load capacities and ratings of appliances, they tend to just wire up everything on two or three lines, and install over rated amp breakers, so you could find your shower line is on a circuit already overloaded, so if you turn on another appliance your RCBO will trip.

 

As stated before a matter of elimination. 

Good luck

20 minutes ago, DUNROAMIN said:

There are many reasons here for tripping.

Please try to understand that MCB, RCBO, RCD, etc. should only trip when there is a fault in the wires connected.  When nothing is connected, the device should not trip.  When the device trips with nothing connected except mains (which is the case here), the device is most likely defective and should be replaced.  There is nothing to eliminate when the device is the one and only factor.

Thanks - that’s what I understood so disconnected load as a first step. Will look at replacing RCBO.

If there is an earth leakage fault, buying and then replacing the residual current device will solve nothing and remove B1500.00 from ya funds.

 

You’ll be back to square one.

 

Find the fault and rectify it.

 

 

@Snackbar please explain (you can use technical terms and drawings if you wish) how an RCBO/RCD with nothing (nada, zip) connected to its output terminals can be sensing an earth leakage fault.

 

Our OP has stated several times that the device trips when power is applied even with all wires removed from the output side.