Lightning (was Wireless file sharing)

Lightning (was Wireless file sharing)

Post by Denni » Sat, 12 Jul 2008 21:24:04



The 1394 adapter won't work anymore on either PC. The notebooks appear
to be working fine otherwise.


It could have. There is a power pole about 40 feet from the tree. But
the surge then would have had to go from my neighbor's house 200 feet
back down to the street, across the main power lines 200 hundred feet to
where my power line taps in, and 300 feet back up to my house.

I also have underground electric running from my house to the barn out
back. So I suppose the surge could have traveled thru the earth into my
house.


I just checked the circuit on the HD satellite receiver with a tester
and it is grounded. I'll double check the other outlets for the 2 PCs
and the cable modem and router. But I have no reason to believe they are
not grounded.

I wonder if the telephone wiring in the house wasn't also somehow
involved. Besides being plugged in to the electrical outlet (via a surge
suppressor), the HD receiver is also plugged into a phone line. And my
phone line did act up later that evening (no dial tone for an hour). I
think the satellite receivers only use the phone line for pay-per-view,
which I never use. So maybe I should just unplug those for now.

Thanks for your comments about completing the circuit first and the
"weakest link" then failing. I hadn't thought of that but it makes
sense.

--

Dennis
 
 
 

Lightning (was Wireless file sharing)

Post by w_to » Sat, 12 Jul 2008 22:42:38


Grounding for safety is not same as grounding for surge protection.
Grounding lightning requires a short connection (ie 'less than 10
feet'). No sharp bends, No splices. Wire not inside metallic
conduit. All ground connections separate until all meet at the single
point ground. Ground wires never bundled with other non-grounding
wires. Grounding must both meet and exceed post 1990 code
requirements. Safety grounded outlets are not sufficient earth ground
for these and other reasons.

All incoming wires must make that short (visually inspected)
connection to the same earth ground electrode - also called the single
point earth ground. Single point earthing is so important that a
utility describes how to correct it:
http://www.yqcomputer.com/

Is telephone involved? Well, the telco installs a 'whole house'
protector for free. Unfortunately, if a surge is permitted inside the
house (more often by AC electric wires), then outgoing surge path may
be that phone line. This is the most common reason (circuit) for
modem failure. Incoming on AC electric. Through modem. Outgoing to
earth via phone line. Damage is more common on the weakest link -
telephone wire side of modem. So many just assume that the surge
entered on phone line because damage was on phone line side. Too many
assume surges crash onto electronics like waves on a beach.
Electricity does not work that way.

Earthing a surge before it can enter the building is called
secondary protection. Every wire in every incoming cable must make
that 'less than 10 foot' earthing connection either directly
(satellite dish, cable TV) or via a protector (telephone, AC
electric). Primary surge protection should also be inspected:
http://www.yqcomputer.com/

Do not assume a safety ground is earth ground. Critical is
something called wire impedance. Wires can have low resistance
(resistance is a function of wire diameter). But for proper earthing,
that wire must also have low impedance (impedance is more a function
of wire length, sharp bends, etc). Why does that incoming cable drop
down to earth ground before rising back up to enter the building?
Wire must first make a very short connection to earth - for surge
protection.