The other day I was called to a appartment that had problems with "electricity in the water". It's a 3x230V system, that means that if I measure phase to earth, I should get +/- 130V. My first thing is to measure the water tap to earth. Result=0V. I then switch on the water tap and measure water to earth. Result 130V!
After examining the situation, I realise that the drainage is in copper (old building). So I measure drainage pipe to earth and bingo =130V. What was happening was the following: There was a fault, one phase touching the drainage pipe (There was no RCD, since it's a old installation). When the tap was opened, the water jet flowed directly to the drainage and the electric current was comming from the drainage via the water flow to the tap!
Anyone had a similar situation?
[This message has been edited by Belgian (edited 10-03-2005).]
On a sink in a toilet. But it energised the drainage of all the sinks of the building! It was sheer luck that the guy who called me was from where the fault came.
After analysing the problem, it became clear how the fault came to be: The appartment above were doing renovation work smashing the floor open without caring about any wires since they thought that all wiring will be renovated. But they don't think about the wiring of the lighting circuit from the appartment underneath that is also passing through their floor.
So presumably it was metallic drain pipe coupled together throughout the building with no bonding at any point.
Those multi-dwelling renovations can be quite a problem in many respects. Even with the terraces common in older parts of British towns (row houses) you can find weird things like a socket in one house which has been spurred from a circuit belonging to the adjacent house.
Good if you're the one getting free electricity and using that socket for your heater I suppose, but not so great if you're paying for somebody else's usage!