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Circuit breakers flashing over or exploding

Johno12345

choosing my words carefully here.

 

Resetting MCBs in a DB or in a machine control panel.  

We have people who are trained in MCB resetting, contactor trips etc inside control panels, and the Schneider MCBs in a dis board are rated for operation by ordinary persons. 

 

I recently lectured someone on the danger of resetting something with the power energised in a control panel, and reminded him that it must be isolated before opening the door (even interlocked isolators can be turned on with the door open. 

 

Well, low and behold, a breaker tripped, panel was isolated correctly, breaker reset, panel turned back on and the MCB and contactor blew up

 

At least it illustrated my point but does this happen much? I have seen it a few times in my years and never in a dis board. Reading the thread about arc flashes has made me think, and if he had his hand on it as it blew up, there would have been an injury of some sort.

 

I'm just thinking about things really, id be interested in your experience of this

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    mapj1: 
    (This is really a piece of light cotton fabric - real cheese comes in plastic or foil these days if you like dairy-lea, but the test methods pre-date that)

    Real cheese comes in real cheese cloth!

    I remember some years ago buying some real Wensleydale at Sainsbury's. The lass behind the counter was having a real job getting the cheese wire to cut until I advised her to remove the muslin.

    True story guv!

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  • 0

    mapj1: 
    (This is really a piece of light cotton fabric - real cheese comes in plastic or foil these days if you like dairy-lea, but the test methods pre-date that)

    Real cheese comes in real cheese cloth!

    I remember some years ago buying some real Wensleydale at Sainsbury's. The lass behind the counter was having a real job getting the cheese wire to cut until I advised her to remove the muslin.

    True story guv!

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