For the non believers and some regs stuff
This is one of those insanely rare cases where I stick 2 fingers up to the regs.
There is no point in introducing a reg (and yes I am aware of the existance and have been in consultation with IET) if the very reg is totally pointless.
Let me attempt to offer some education please.
The flow of water in a pipe and current in an electrical conductor follow fairly similar laws of physics and as water can be seen it's easier to demonstrate the point that way.
Lets get a standard garden hose of some random length, let's assume 20m as that seems to be quite common. Connect one end to a tap and plug the distant end, drill holes in the pipe at 1m intervals, say 5mm diameter.
Now turn the tap on full and observe the water flowing from the holes.
I'm sure we'll all accept water will initially flow from only the hole closest to the tap and increasing one by one it will eventually flow from all holes.
Comparing that with a CU we have a conductor (hose pipe vs busbar) with periodic current outlets (holes vs copper branches) and we have a current flowing (water vs electrons)... Yes all very simplistic isn't it.
Let's put some timings on the hose pipe and come up with a figure of say 1 second delay between the time the water takes to flow from each hole, assuming we have 19 holes the current has been flowing from the first hole for 19 seconds before the last gets wet. In the case of the surge protection being on the end of the hose that's 19 seconds of surge/excess pressure before the protection device can even begin to think about doing any work.
Now we drain the hose out and set up just as before. We now apply water pressure for only 5 seconds (as surges are usually time limited), current flows from the first 4 or 5 holes but no further, it doesn't even reach the protection device.
Those who are now getting very confused, my apoligies however the very simplistic comparison has validity as electrical current flows in a conductor at a finite speed. Just in case there are non believers, look it up on Google etc and while there look up 'coax stub' and find out where this detail is actually used in the real world.
For the benefit of the tape I have found myself looking at vapourised radio equipment where the correct practices have been ingored (And by vapourised I mean big chunks of electronic equipment being turned into molten blobs and hurled against walls etc) and only a few feet away similar equipment being still serviceable where the protection procedures have been correctly implemented.
Regs or not... pointless if incorrect.
