[TowerTalk] Shack wiring

[Jim Brown]

On Fri, 19 Mar 2010 19:31:11 EDT, HansLG at aol.com wrote:

> 
>Hi Jim,
> 
>I still don't get it (maybe because I am dumb). At my service entrance  is 
>a protector that connects has two MOVs, one from each leg to ground.  Ground 
>in this case is the same as neutral 

That's very good (assuming it's a good unit). 

>At the water pump is also a protector  
>that has MOVs frm the two legs (the pump is a 240 V pump) and ground. 

What is that "ground?"  EXACTLY where is it connected? Is there any control wiring 
running from the water pump to anything else?  How much inductance is in the green 
wire between there and the service entrance ground?  These additional MOVs have the 
potential to cause a destructive failure. It is SAFE to have an MOV from Line to 
Line at that point. 

>In the 
> shack I have a protector that connects MOVs from neutral AND the hot 120 V 
>leg  to ground. It also incorporate a protecting circuits for my phone, it 
>has two  gas discharge tubes between the line and ground. 

Same questions -- what is that "ground?"  EXACTLY where is it connected? Is there 
any control wiring running from the shack to anything else? How much inductance is 
in the green wire between there and the service entrance ground?  These additional 
MOVs have the potential to cause a destructive failure. It is SAFE to have an MOV 
from Line to Neutral at that point. 
> 
>Should I disconnect al MOVs that are connected to ground ??? As I wrote to  
>you earlier, my house has had two registered lightning hits (and possible a 
> couple of more we don't know about) and everything survived.
> 
>Can anyone describe the failure mode that makes the MOV from the hot leg to 
>ground bad?

I've done that several times in earlier posts. See also pages 29 and 30 of 

http://audiosystemsgroup.com/SurgeXPowerGround.pdf

73,

Jim Brown K9YC