Well done John Rumm

[Doctor Drivel]

You must eff off you are a lunatic.

[Doctor Drivel]

This man is a cowboy.

[Doctor Drivel]

..Maxie talks about self abuse, I tell you not ..the man who climbs trees in polka dot ..why does he wear his pretty frocks ..without any matching bobby socks

..he boasts of making loads of dough ..while on beaches in his chiffon flow

..what sad bastards give Maxie a ready? ..are they sex mad people mentally unsteady?

..it's clear for all and plain to see ..how Maxie earns money on a beach up a tree ..the prime attraction causes people to frown ..the sight of fat Maxie in a flowing ballgown

[brass monkey]

[Andy Wade]

Something like that, perhaps combined with vibration from passing heavy traffic, etc. - or possibly even the result of an original manufacturing fault.

Single module RCBOs, as you infer, do use electronics and could be subject to EMC problems (although that's not something I've ever come across[1]). This type will also trip if they detect more than 50 V between the neutral and their functional earth connection. That could lead to tripping in a TT-earthed installation if the incoming TN-x neutral has come adrift from earth or is unduly noisy, perhaps. I wouldn't call that nuisance tripping though - the RCBO would be trying to tell you something!

[1] EMC standard EN 61543 applies to all RCDs (i.e. RCCBs and RCBOs).

[The Natural Philosopher]

Well it seems Drivel is a lot better at doggerel than plumbing.

Time to change the day job Drivel?

[js.b1]

What make was the MCB? A few MCB have been subject to recalls recently, may be worth sending it to the manufacturer for checking.

MCB trip current does de-rate with rising temperature, so in theory a loose busbar screw can cause things to get warm enough to de-rate the device. In practice I suspect an MCB would have to get hot (smelly, case melting) with a high current load for some time before such behaviour is noticed, by then it is probably a "Wylex open backed fuseboard fire". A cheap battery powered smoke alarm in an area containing a CU and old service head is a good idea, particularly if located under the stairs.

[Doctor Drivel]

This snotty uni man is known to be mad.

[Doctor Drivel]

You are an idiot.

[Doctor Drivel]

Maxie, and who was up a tree in a frock on a beach? All interesting stuff. Maxie you just clearly fabulous. How is the Paddy band going Maxie? Are you still dancing with the turned down wellies on? What a man! What a man!

[Doctor Drivel]

Fantastic! Thank you leccy nerd. Thank you.