A dull thud can be water hammer from a neighbour?

However that does not usually make the lights dim... if it IS the supply cable then the eventual bag can be quite destructive. It comes down to how fast a fault disconnects and how much moisture there is around - moisture flashes to steam and this can be particularly brutal under a concrete floor.

400A upstream fuse may need 4500A to blow 0.1sec which is 1 megawatt of energy shovelled into moisture which is going to become steam and expand in that 0.1sec.


It sounds old enough to have a Paper Insulated Lead Covered (PILC) cable, which might have been bilked by a conservatory spade or simply a joint that is going high resistance, failing, moisture ingress etc.

A high impedance supply will cause light dimming with high load, as will a stuffed joint box. Freezers require a fair whack to start which is enough of a load, and can bang if they do not start due to high impedance supply. So the two may be interconnected even if the fridge does not appear to be the fault.

Defrost the fridge, switch the conservatory off, diary time. DNO may want them to do that before they come out. Steep sided crater in garden however will not be an asteroid, it will be a cable, wrong blast profile :-) ... could be a mole after Newcastle Brown Ale of course... but that is another matter.