[RFI] What is a MOV

[Jim Brown]

Series-mode protectors are only practical on branch circuits.  I use 
Surge-X in my ham station, my wife's sewing machines, our computers, and 
home entertainment system. I have a Joslyn whole house protector at the 
service entrance.


73, Jim K9YC


On 1/11/2019 1:20 PM, D C _Mac_ Macdonald wrote:
> Hi, Jim.
>
> I'm convinced.  Can you recommend a specific Surge-X whole house 
> protector to acquire for one's own house for 125-0-125 Volt 200 Amp 
> service?
>
> 73 de Mac, K2GKK/5​
> Since 30 Nov 1953​
> Oklahoma City, OK​
> USAF, Retired ('61-'81)​
> FAA, Retired ('94-'10)​
>
> *From:* RFI <rfi-bounces at contesting.com> on behalf of Jim Brown 
> <jim at audiosystemsgroup.com>
> *Sent:* Friday, January 11, 2019 14:47
> *To:* rfi at contesting.com
> *Subject:* Re: [RFI] What is a MOV
> On 1/11/2019 8:22 AM, Ken Winterling wrote:
> > The Metal Oxide Varistor or*MOV*  is a voltage dependent, nonlinear
> > device that provides excellent transient voltage suppression.
>
> Delete the word "excellent" from this sentence. They are, indeed,
> ubiquitous, but they can also create more problems than they solve. They
> should NEVER by used on branch circuits -- inside equipment or in outlet
> strips when there is any interconnection between equipment plugged into
> different outlets, or which is grounded at points in addition to the
> green wire. This is because MOVs conduct any power line spike onto the
> green wire, raising the potential of the "ground" in the equipment. The
> increased potential will be different at each piece of equipment
> (different induced current from the strike, different length of green
> wire), and the potential difference fries the interconnected equipment.
>
> We learned this the hard way in the world of pro audio, where equipment
> for large installed sound systems is spread out over a wide area. And
> I've heard many reports of computers linked by wired Ethernet getting
> fried by a nearby strike.
>
> The ONLY good place for an MOV is at the power entry panel (a so-called
> "whole house protector) where it is bonded directly to the ground system.
>
> The only good (and safe) surge suppressors for branch circuits are
> "series mode" types, which store the energy from a strike in a large
> inductor, then discharge it slowly after the strike. The pro audio world
> uses products made by Surge-X. Brick Wall is another mfr.
>
> 73, Jim K9YC
>
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