D
Deleted member 9648
RCBOs with a solid neutral are far from ideal with any earthing system.
If there is a neutral to earth fault then the rcbo will react by disconnecting the line and not actually disconnect the fault.
Thus it appears to the user that a fault has occurred but it is now disconnected because the protective device has operated, when in actual fact the fault is still there.
Plus of course you now have a portion of the neutral current from the entire installation diverting through the fault.
Additionally manufacturers have their own requirements for maximum Zs for correct operation of their single pole RCBOs, which may not be achieveable on a TT system.
The point that springs to mind here is that a N-E fault on a system with no RCD element will remain undetected with the same risk of neutral current diverting down the parallel path caused by the fault, at least with a SP RCBO the user will have an indication that there is a problem. I've not come across any manufacturers who give their own max Zs values for standard RCBO's, can you give an example of this?