MCB tripping and not switching off power

[ARW]

A bit of a flash as the cable popped out of the terminal block and touched the earthed light fitting.

Now I would have expected the MCB to have tripped, however power was still on.

So a long trip to the DB only to find the MCB HAD tripped - well it was in the off position.

I turned the MCB back on and then off and it killed the power (and all the lights in reception leaving some very unhappy looking people in the dark).

Never seen that one before. I have seen plenty of MCBs in the ON position not letting power through but never this way around.

[harry]

Points/contacts welded together??

[Brian Gaff]

Probably gave the spider living inside a very bad day though. I would replace it just in case, you definitely do not want that kind of thing going on in a public building. Brian

[spuorgelgoog]

Working live, naughty boy!

Ah! You can now sell them some emergency lighting. Not sure how you'll fit it without turning the power off ...

Owain

[Robin]

every problem is an opportunity ;)

- sell them current injection testing of all their DBs (at premium evening/weekend rates to avoid disruption of business)

- report to Electrical Safety First and suggest they lobby for current injection testing to be made part of compulsory quinquennial EICRs (gives you more work in future years - though best if you have an apprentice to carry the kit if it's still like the only set I ever saw in action)

[Brian Gaff]

It might have just been a too heavy light shade of course

Brian

[Graham.]

On Sat, 9 Dec 2017 08:23:04 +0000, ARW coalesced the vapors of human experience into a viable and meaningful comprehension...

Counterfeit MCB? Wylex model that was subject to a recall?

[ARW]

MEM 1980's installation.

[Rob Morley]

Those of us with special training are permitted to do that. :-)

[whisky-dave]

But only when working when posting they seem particualy brain dead. :-)