Hi John:
> I do have one question for the group just for my own knowledge...back in my
> TUV days I worked almost exclusively with IEC60950 and seem to remember
that
> a class II product can have a functional earth connection provided Primary
> and other hazardous voltages are insulated from earth by reinforced
> insulation. In this scenario even thought the product has an earth
> connection would it still be considered class II with regards to the
> IEC60950 standard and have to be marked as such?
> Maybe it is semantics as you reference "protective earth" so it must be
> class I as opposed to functional earth which is not relied upon for
> safety.........
Yes, a Class II product may have a functional earth.
However, the standard does not define whether that
functional earth may be by means of the PE in the
power cord.
I have always presumed that the functional earth of
a Class II product is by means of signal (functional)
interconnections to other products that have their
functional earth connected to their PE terminal.
We don't have functional earthing through a power
cord and appliance coupler. These are always built
as PE conductors. The appliance coupler has basic
insulation between the mains and the PE terminal.
So, the use of an appliance coupler REQUIRES that
the earthing circuit at the appliance coupler be a
PE circuit. (Reference IEC 60950-1, sub-clause
2.6.2, last dashed paragraph.)
If the product has an earthing connection via the
power cord, then how do we tell the user that the
earthing scheme is functional, not PE? We cannot
mark the unit with the double-insulation mark.
(Reference IEC 60950-1, sub-clause 2.6.2, last
dashed paragraph.)
My conclusion is that any product with a PE
conductor or terminal (i.e., 2-wire + earth) is a
Class I product.
Any product without a PE conductor or terminal
(i.e., 2-wire) is a Class II product.
Best regards,
Rich
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