A garbled message from a good client, pleading for assistance. Not the sort of thing you want to hear on the Friday evening before Christmas when all good electricians are wrapped around a well-deserved pint or at home snuggled up to a roaring fire or whatever one does with a heat pump.
Anyway, one of my guys was on his way home and reluctantly, but in good grace, agreed to attend. When he arrived, the NIE had already pulled the main fuse, claiming the fault at the property was “back feeding” and that the supply would not be restored until the fault was rectified. The client, with a house full of family and guests was beside himself. He had hooked up a small generator, you know the way, fed into a 13A plugtop and connected to a socket.
There really wasn’t much my guy could do, other than make a better job with the genny. So, he phoned me to report with the client listening in on speaker. The issue was in one of three well-to-do rural properties all in a cluster, all supplied via the one DNO transformer and all TT. Single-phase 20-way board all populated with RCBOs. The client reported what the man from the NIE said about something "back feeding", but it didn’t make much sense. The penny dropped, however, when the client said that the weird thing was that when his driveway lights came on, the neighbour’s EV stopped charging!
Now on video, I asked my guy to open the consumer unit and show me the devices within. My hunch paid off, sure enough, lost in the run of RCBOs was a 10A MCB supplying the driveway lights. Why? Well, the RCBO kept tripping, so the client swapped it out for something that didn’t trip!
I assume that the neighbour’s charge point O-PEN monitoring dropped out the contactor when the neutral/earth voltage jumped out of acceptable limits.
For the moment, the power has been restored to the property, the client is happy, albeit without his driveway lights and I am content to speculate on the issue while snuggled up to my very un-renewable coal-burning stove.
Merry Christmas!
