1960s Earthing/ Bonding question

[Ragnar_AT]

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).

 

[ericmark]

It depends on the manufacturer, some RCD's the test button connects around the CT coil, some connect to earth, the whole reason for finding the fault was the test button did not work, so I got my RCD tester to investigate and that did not work either. It was over 10 years ago so can't remember all the details, I think the idea of an insulator on the gas supply would prevent many fires, where the pipe can't take the earth current, I think there is an insulating block, however it has been known for the earth bond to go on the wrong side of them.

The water pipe is clearly water cooled, so not the same problem.

My oil pipe clearly comes from outside into the house, but not a clue where, some where I assume behind kitchen cabinets, but I have never looked for either the water or oil pipes to see if there is an earth bond.

My parents got gas a lot latter than when house built, in 1954 when house built it was a steel-working town, and coke was very cheap, so everyone heated and cooked with coke, coal was only used to light the fires, so gas meter was actually installed outside on the porch, always thought strange, but the underground pipes must have been plastic by then, we had an offer by the "electrician" fitting the electrics for the wet room, to change whole consumer unit for £100 extra rather than add a second small consumer unit, and we said yes.

I found he had used the GPO party line earth, which was far smaller than required, and only the wet room circuits were RCD protected, and when I came to test, I could find no sign of the original earth, the house was converted to TN-C-S but it clearly was not TN-C-S to start with, and since I had as a child blown a fuse with a line to earth fault, it much have had an earth to start with, but could find no sign of an earth ever being there.

Hence "electrician" in quotes, as I can't see how an electrician could have fitted a consumer unit without testing, the builders doing the wet room ran off, and we had problems with the LABC as it seems they had not registered the work, the builder went to the wall, and stopped trading, and we got no paperwork from them, we did get the completion certificate from the LABC in the end, however it did make me wonder how many other homes that "electrician" had worked on, and how many had no earths?