I went to look at a job today which was having problems, the RCD main switch was tripping intermittently (every couple of days at random times).March this year they had the 8 way CU replaced with a RCD main switched one, no EIC and no Part P cert.... so they got someone in to do a PIR which had a couple of failures which were then put right.
As I said, since this job was done it has tripped out now and then; the guy who did the PIR has been back once or twice and could only find a burnt out socket, which he replaced and hoped that had sorted the fault. It has since tripped again and as he is based out of area he recomended that they get a local spark in to have a fresh look (that's where I come in).
When I get there all the electric is on (fault not showing its self) so even if I tested it I wouldn't find a fault (PIR cert on site to look at), all the apliances are new as it is a young couples first house so all I could do I tell them to unplug items that they aren't using and to make a diary of events. If everything stays ok then they could plug in more and more things over a long period and see how it goes.
The main problem as I saw it was that even though it had a PIR carried out they did not mention the RCD non-compliance, so I recommended that they replace the RCD for a main switch and MCB's for RCBO's (essencially a CU change, but keeping the enclosure), while this probably won't cure the fault it will limit it's effects and narrow the search!!
BTW it's a TNS installation and I did enquire wether neighbours were having problems and thay said they weren't. I also tested RCD (0 and 180 deg) and it tripped well within limits 1 x 18mS 5 x 8.8mS Ramp 23mA (1/2 and manual both OK)
Any other ideas??
