[TowerTalk] Whole house surge protectors

[Gary Schafer]

Some may be surprised upon opening up one of those whole house 
protectors to find that most are nothing more than a can filled with 
sand and a heavy duty spark gap inside. The sand is there to quench the 
arc after the surge is over. They do work though.

73
Gary  K4FMX


Jim Brown wrote:
> On Thu, 29 Sep 2005 14:52:11 -0500, Dave NØRQ wrote:
> 
> 
>>I've never had a problem with it -- no RFI from it, and it has never acted 
>>up, even with 1kw of RF quite close to it.  Nor have I had any equipment
>>damanged by lightning -- 
> 
> 
> It's important to understand what these devices do. These "whole house" 
> units are simply BIG MOV's that attempt to conduct the surge to "short it 
> out." In doing so, it must GO somewhere -- that is, current flows in some 
> complete path. Remember that the neutral is bonded to ground at the service 
> entrance, so there is no need for a protector between neutral and ground. A 
> line to ground protector conducts the surge to ground, so when a surge hits, 
> it will raise the potential of the safety ground (and neutral bus) by an 
> amount equal to the IZ drop between the panel and whatever lightning thinks 
> "earth" is. When you say "line-to-line," I assume you mean across the 240 
> volt secondary of a 120-0-120 circuit.  
> 
> 
>>but then, all the electronics plug 
>>into "real" lightning protectors (usually TrippLite) before plugging
>>into the wall
> 
> 
> Your definition of "real" in this case is flawed. Nearly all AC line 
> "lightning protectors" are nothing more than MOV's connected as noted above. 
> When they take a hit, they shove the surge into the equipment ground wire at 
> the outlet where they are plugged in, raising the potential at that outlet 
> in the presence of a surge. If equipment plugged into a "protected outlet" 
> is connected by low voltage wiring to equipment plugged into another un-
> protected outlet, or even a DIFFERENT protected outlet, there can be large 
> potential difference between outlets that can blow up equipment. Thus, 
> typical power-strip MOV protectors are NOT "real" protectors. 
> 
> The "real thing" includes 1) a good whole house protector and/or 2) a 
> SERIES-mode protector like those that SurgeX makes. I use SurgeX boxes, and 
> plan to add a "whole house" unit at the service entrance. 
> 
> And, as has been pointed out on several occasions, it is critical that other 
> lines (telco, antennas, etc.)that can bring lightning into the house be 
> bonde and/or protected AT THE SAME POINT as the power line. Tom Rauch has 
> pounded on this for quite a while, and he is right on. That's often a lot 
> more difficult in some installations, but it's the right way to do it. 
> 
> Jim Brown  K9YC
> 
> 
> 
> 
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