can mcbs fail?

[gazandlucy]

I was changing over kithchen lights and when i turned the mcb back on ...nothing. all wiring is correct but still no power ...no trip or rcd trip??

I checked the mcb connection which isfine an when the top red wire outlet from mcb connected to next 6amp mcb(smoke alarm) all lights work??!!

Can mcb's fail? why and is there an underlying problem.

Thanks for any help!

 

[Windup1]

An mcb is an
electrical component therefore could fail, remove faulty mcb n replace is cheapest option