[RFI] ISOBAR

[Pete Smith N4ZR]

I guess what I was asking was whether the snubbing at the power entry 
would allow MOVs to work for the branch circuit protection a 
cost-effective share of the time.  I have experienced problems with 
Ethernet EMP pickup, but so far my cascaded MOVs have done the job, even 
when I took a direct hit on my tower.

73, Pete N4ZR
The World Contest Station Database, at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000

On 9/17/2012 12:46 PM, Jim Brown wrote:
> On 9/17/2012 3:20 AM, Pete Smith N4ZR wrote:
>> Our whole-house protector (from the power company) comes with good 
>> insurance for things inside the house provided that you cascade a 
>> point-of-use surge protector.  They seem to assume that the latter 
>> will be MOV-based.  Is this a way to get around the IR/IZ drop 
>> problem so that one doesn't have to spend $200-500 for even 
>> consumer-grade Brick Wall products? 
>
> I'm not sure what you mean by "get around" the problem.  What the 
> whole house solution does is snub a strike coming in on the power 
> line, but voltage and current can still be induced on wiring within 
> the building. The function of a branch circuit protector is to protect 
> against that.
>
> MOVs are REAL CHEAP -- much less than a dollar. Most of what you pay 
> for MOV-based protectors is for packaging and marketing. Series-mode 
> protectors are expensive to build, for reasons that are obvious when 
> you see what's inside.  There's a BIG inductor that stores the spike, 
> then discharges it slowly. It costs money to build something that will 
> reliably handle the energy of a strike, which IEEE studies say can be 
> as high as 6kV in a premises that is properly wired.
>
> The big sound systems I designed used racks full of power amps, and 
> often a rack or two of low level signal processing.  Often the bigger 
> power amps were only one or two to a circuit, so the cost of 
> protecting them could be a third the cost of the equipment. For that 
> reason, I did not specify protectors for the amps, but did for the 
> signal processing, where an entire 7 ft rack (or even two racks) could 
> be on the same circuit and cost a lot more than the two amps I could 
> put on a circuit.
>
> So the short answer is that I don't know of a good lower cost solution.
>
> 73, Jim K9YC
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