> On Mon, 05 Mar 2007 19:40:20 +0000, Rick Stealey wrote:
>
>>If I understood W8JI recently, Tom said MOVs should not be
>>installed in a
>>piece of equipment, forcing the surge to green wire
>>ground, but rather
>>should only be at the service entrance (or single point
>>ground?).
I actually said the MOV can't connect to the safety ground
or chassis, it can only connect from hot to neutral or
across the line on a 240 system.
We aren't allowed to connect anything to the chassis or the
safety ground (including control or filament transformers)
that can provide any current because an open safety ground
would present a hazard.
I sometimes use a UL/CSA rated bypass cap from neutral to
the safety ground (or chassis) when it is the only way to
get rid of RFI, but I'd certainly never use anything that
might provide a fault path from the hot mains terminal to
the safety ground! There are accepted bypass caps but MOV's
hard-fault with lots of current, so you wouldn't want one in
a position where it could dump the power line hot lead to an
exposed conductor like the chassis.
73 Tom
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