Why would the test button not work downstream of an ELCB? All it does is connect a resistor between L on the supply side and N on the load side (or vice versa), which always creates an imbalance that should trip the RCD.
Inducing an earth fault definitely wouldn‘t have tripped the RCD if the CPC was only connected to the load side of the ELCB. In that case the ELCB should have tripped though (apparently most multi-function testers also trip an ELCB in RCD test mode, I know people who‘ve tried it).
In Germany all bonding was to be to the electrode, any loads connected to both water or gas pipes and the CPC were required to have insulated pipe connections (I suppose rubber hoses would have been the most likely thing to use).
Inducing an earth fault definitely wouldn‘t have tripped the RCD if the CPC was only connected to the load side of the ELCB. In that case the ELCB should have tripped though (apparently most multi-function testers also trip an ELCB in RCD test mode, I know people who‘ve tried it).
In Germany all bonding was to be to the electrode, any loads connected to both water or gas pipes and the CPC were required to have insulated pipe connections (I suppose rubber hoses would have been the most likely thing to use).
