nospam wrote:

It's just I thought it would trip to "off" if it failed or take the
rcd with it. No buzz, no smoke, no burning smell, nothing

One possibility that can occur (although rarely) - especially if you are
close to a substation - is the fault currents that can flow may exceed
the breaking capacity of the MCBs. This can result in them failing
terminally when attempting to clear a fault.

(most MCBs can break upto 6kA, although some designed as plug-ins for
old wylex units can be as low as 3kA)



--
Cheers,

John.

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