I know I’ve posted this before abot 15 months ago but it’s worth posting again. Nobody was getting shocks but it could have been very nasty.
A fault I had many years ago in my own house. I’d just installed gas central heating, the very last job for me to do was connect the gas pipe to the gas meter. Touched the two ends of the pipe and got a spark! Not good thought I, well to hell with it jammed the pipe together and soldered the joint. On putting a clamp meter round the pipe found 25A flowing through it. Turned off supply to my house, still 25A, I’m getting confused at this point. Phoned electricity board, and after speaking to one of their engineers was told to keep both supplies turned off, they’ll get back to me. Not 2 mins later phone rings, we’ll be there in 20 mins! 4 vans and 2 overhead line wagons showed up! I did live in a rural area so supplies to the road were overhead. Much head scratching followed, at one point we disconnected the gas meter and slung that out in the back yard. In all seriousness this was the point the gas meter reader showed up. It was decided to disconnect the entire road from the supply. By this time I’m not the flavour of the month with the entire road, we’ve now got 12 houses with out supply. The OH crew found a burnt line tap on the neutral. Further tests showed a neutral earth fault somewhere in one of the 12 houses. As I knew all the neighbours I got delegated to got to each house and isolate the supplies, how come this ended up as my job? Eventually there’s a shout from the OH crew as I isolated the furthest house on the road, “faults gone”. Electricity board senior engineer then goes in to “Hitler” mode, tells my neighbour “unsafe installation your supply will be disconnected until rectified”. While the OH crew are repairing the connections to the road I hijacked the apprentice that had come with the board and checked through the house. The apprentice found the neutral fault in a socket, the facia screw had bitten in to the core. OK now neighbours supply can be reconnected as well.
Now think about it the neutral for 12 houses was going through one 3.5mm screw. The house was bonded to the water pipe only. The current travelled along the water pipe until it got to my house, I’d just rewired and fitted CH. So it was a case of if it doesn’t move bond it, the current then went through my house and out through the gas pipe and spike. (I’ve never understood why a steel gas pipe is a better earth than lead water pipe, but it always is)? Just how in the name of god my neighbours house didn’t burn down I’ll never know. The fault must have been there for years.
