So whats is your ideas...5 amp mcb with main switch 30ma rcd....nice house , dry etc ...put any combination of lights on and after around 4-5 minutes mcb blows.....the lambs are varied but i can not see any overload and it will do it with only a handful on...if you leave say 1 or 2 lights on it will not blow...and any selected but add load in any are even light it blows...so far my views is could be mcb fault but then why would it not blow with less lights...small fault...but why would that not take out rcd ?..and this has been doing it for years not short term...a mcb blowing seems overload but i can not see that as it does it well in on loading...any views ?