This is from personal experience 35 years ago and shows the dangers of N→E faults. Lifted from an old thread.
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
I’m confused, the wife is frantic,
no gas or electric now!
Phoned NWEB, and after speaking to one of their engineers was told to keep both supplies turned off, they’ll get back to me. Not 2 minutes later he calls back, we’ll be there in 20 minutes! 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 N→E fault some where in one of the 12 houses. As I knew all the neighbors I got delegated to go 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”.
NWEB senior engineer then goes in to “Hitler” mode, tells my neighbor “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 N→E fault in a socket, the fascia screw had bitten in to the core. OK now neighbors 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 traveled 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 (14[SUP]th[/SUP] edition), the current then went through my house and out through the gas pipe and mesh*. (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 neighbors house didn’t burn down I’ll never know. The fault must have been there for years.
* The house was on high ground with very shallow top soil. Get down 3’and clang, the rod hit bedrock. I was friends with a local farmer so he excavated most of the back yard and I put a mesh in (I’d recently demolished a substation so bought the mesh as scrap). It still couldn’t match a 50 year old 500’ long 2” steel pipe in what was after all that time in well consolidated ground.
Years later the gas board replaced the pipe with plastic. Didn’t take me long before I’d welded a stud to the redundant pipe and tied it to the mesh. Don’t ask me the reading it’s 25 years since I left that house.
