Worn out MCBs - truth or nonsense

[spongobongo]

Please settle an argument for me.

I've been told that MCBs eventually weaken if they keep tripping. Sounds like a load of guff to me but I'm in no position to argue the toss.

What's the definitive answer?

 

[1john]

yes, or if they are run at max or over max capacity over a long period of time.

 

[Risteard]

There are two values listed on circuit breakers to BS EN 60898 (Icn and Ics).

These give the current that the device can break and remain serviceable, and the absolute maximum value that it can safely break (but may no longer remain serviceable).

 

[holmslaw]

..

 

[Spark123]

An MCB basically relies on a spring to operate, eventually I'd expect it to weaken but you're probably looking into the 1000s if not 10,000s of operations.
The contacts will probably be shot at by then anyway.

 

[holmslaw]

..

 

[jaysean1]

By rights if a MCB trips 3 times, it should be changed,
but how many do inc myself

 

[Mickymoody]

Surely they are designed to 'fail safe', so best practice is to replace if continually failing (or fix the reason why they are failing, if not the unit itself), there must be manufacturers data regarding this?