So - the whole lot went again at the weekend (Sunday of course) after nearly
2 months of working faultlessly. Sudden trip - no way to reset the RCD pretecting the whole lot (100mA).Sparky was and still is on hols in Wales - and after a quick chat - I decided to work this thru on my own.
Popped the front off the fuse board and was amazed at the number of wires - bit daunting.
Started by dropping out the live of each circuit - seeing if there was any immediate change. No change - still can't re-set the RCD.
So start tracing back the neutrals from the bus bar to match up with the lives - the drop one circuit at a time - including dropping out of the equation and patching in with a long bridge all the works just done in the kitchen. Still no go - right up until I disconnect the last circuit - WATER HEATER - now the run to the boiler post all the works.
Back up it comes. Cue confused eyes.
Plug everything back in - except the boiler cct - plug all the applainces back in - re-create the circumstances under which it went - nothing - worked fine.
Cue curious eyes. Re-connect suspect circuit - RCD won't go live - hmmm - arse - it's the boiler - oh well - it's warm outside and I can get the telly back on in time to watch top gear and keep the beer in the fridge cold enough and avoid a mercy run to the folks with the contents of the freezer - result.
Stop and think about things - the boiler is protected by a fused DP switch - wonder what's going on - so disconnect the live and the neutral at the switch - and try again - huzzah - the RCD goes on. Odd.
Probably well against regulation (but I know it's a straight run - 1 join as far as the switch on 40a cable - I put a socket on the end and plug in a kettle and fire it up - figuring the boiler is 150w - the kettle is ~3kw - this should put a decent load on the cable and if it's screwed possibly cause it to dump - nowt.
carefully re-wire switch with boiler and cable meeting up. Reconnect all - check - double check - and fire it up - and all is fine!
So - either the boiler has an earth leak that's borderline enough to cause the RCD to drop out - or - there was a fault that I missed either in the fuse board or at the boiler end.
Either way - the electrician is going to come back next week to re-check the circuit - but it looks like either the switch is up the poke (unlikely) - or - the boiler is iffy.
Thanks for all the pointers you all offered before. Although I still don't have a definate finger of blame here - I am much better acquainted with it all - and reckon that if push came to shove I could replace the whole lot (fuse board) with a split load so that we could at least maintain some form of service if things were to go a bit awry. I know also know that we do have an earth provided by the leccy company - and our meter makes a really dodgy buzzing and popping/bouncing noise all the time - even when there's no load on it (which is a little annoying when you spend the afternoon with your head close to it - and is now more or less impossible to miss while sitting in the lounge) - so I'll call the leccy board about this.
So - progress (of sorts) - I'm quite chuffed. I did find lots of loose connections in the fuse board which can't be attributed to the sparky (not the ccts he played with) - and many of the neutrals were loose. That - and a bleedin great screw dropped out of the guts of the box once I got to connecting/disconnecting things - can't help but think a 6x1.5 woodscrew can't have been doing much good lost in the works!!
Thanks all once again, really appreciate it.
If it goes south again - think I'll get a megger (can you rent for a couple of days? I found a place selling them for a couple of hundred quid today - but that's a tad overkill) and test it top to bottom - and perhaps replace the fuse board...
On that topic - how do you do this without pulling the master fuse?? I know it can be done as I've seen it - but personally I don't like buggering about with something that's 100A @ 230v - and I can't get wellies in my size ;-)
Cheers Dan.