locking a mcb in the on position

[Farmelectrics]

is it allowed to lock a mcb in the on position data centre spark informs me they have mcbs locked in on so no one accidently nocks breaker off i tell him that could be dangerous as the breaker will not trip in fault condition but he tells me that thermally the breaker will still trip anyone come across this your thoughts please chaps

 

[Engineer54]

Getting back to the original question... I wouldn't say it's a common occurrence to lock an MCB/MCCB in the ''ON'' position, but it can have it's uses in some situations, and is certainly not against any regulations that i know about.

I don't know where this use of ''OFF LOAD'' isolators has come into it, especially on motor circuits. These type of isolators are generally only used as a means of local isolation for maintenance purposes, when working on plant etc, after a full isolation procedure has taken place and are only capable of being locked in the ''OFF'' position....