Gentlemen,

I need your collective memory.

I have an engineer that wishes to design a protection mechanism to apply a
short circuit across the mains in order to open a protection device
upstream to stop an over-heating fault. The protection device would be in
the product, we are not talking about depending on the protection in the
service panel. I will not let them go there.

I remember somewhere in the past that one of the standards, or perhaps a
country deviation, specifically forbid shorting the mains as a means of
protection but I cannot find it. I think it is from the era when we were
using IEC 380 or 435 and UL 478 but I am not sure.

Can someone out there point me to the standard and clause? or perhaps the
deviation or an OSM decision?

I am looking for all of the arguments against this practice I can pull
together because I do not feel it is sound. It is one thing to crowbar the
output of a power supply to protect an expensive logic board from a power
supply over-voltage failure. It is quite another to short the mains input.

Many thanks,

Gregory H. McClure
Lexmark Product Safety
859 232 3240 office
859 232 6882 fax

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