I have several surge/RF filter devices made by Tripp-Lite and they have
3 MOVS in them. They also have UL/CSA rated caps across all 3 wires but
the caps to the neutral line have smaller capacitance so as to no trip
GFI devices. Everything in the unit is on the downstream side of a
circuit breaker which is in the hot lead. No fault can cause continuous
neutral currents that way. I see no problem with this design and should
the surge/RF filter be placed a long way from the service entrance, your
local equipment does have a measure of protection for large voltage
spikes from either hot/neutral to the chassis alievating the local
equipment to have to sustain this brief voltage.
73,
Larry, W0QE
Tom W8JI wrote:
>>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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