Is anyone aware of a reason why, after tripping due to a fault (some hours previously), a reset MCB would delay the re-connection of power for 3 - 4 hours. On subsequent checks the MCB appears to work correctly and the operating lever etc seems normal.
If the thermal trip part of the breaker is still warm after overload it will not allow a reset. However, in that case some breakers allow the lever to look like it is in the on state, without priming the spring mechanism, so if it is one of that design, you may look quickly and think it ought to be on when it is not.
Normally though that would be a matter of a few tens of seconds to cool off, not hours, unless another source of heat is nearby, so maybe the breaker mechanism is wearing and does not engage reliably - they are not meant to operate that many times, especially into a fault, before they need changing.
