AW: To earth, or not to earth...

[Ingo Debus]

Martin Czech wrote:
> 
> By the way, metal chassis should be connected to earth, i.e. power
> supply earth, water pipe, whatever. To avoid electric shock hazard.

Is there any regulation (VDE or so) that says circuit ground has to be
connected to Protective Earth? This connection is made in many devices
and it causes trouble again and again.
If there is such a regulation, what about laboratory power supplies?
They always have earthfree outputs.
If there is not, why do so many manufacturers implement this connection?

Regards, Ingo