Re: Driving a seperate ground rod
- From: bud-- <remove.BudNews@xxxxxxx>
- Date: Tue, 24 Jul 2007 11:35:36 -0500
Terry wrote:
I think the electricial service in my house is adaquate, but I suspect
that my copper pipe is not.
Would it be legal to drive a seperate ground rod to bond the copper
pipe in my basement?
We were on a well at one time but now we have county water. The
piping from the county to the house is pvc.
The reason I suspect the copper pipes is that during an electricial
storm I lost a modem once. It would power up but the phone line part
would not function. The incoming phone line is bonded to the copper
pipe in the basement.
I now have two computers that I think the mobo's are dead. There was
a storm before I came home. The computers are plugged into a surge
suppressor and a UPS. The power supplys in the computers are good,
but I strongly suspect that the mobo's are toast. I am afraid they
took a hit from the Cat 5 coming from the modem. The cable is also
grounded with the same copper pipe.
The sad thing is that the UPS does have protection for the Cat 5
cable, but during some trouble shooting I had done in the past the Cat
5 was not re-hooked to the UPS.
When the water supply was changed to PVC you lost the system ground. I agree with RBM, you need at least 1 ground rod. Ground rods are not very good, but they are far better than what you have now - nothing.
Starting with the 2005 NEC, for most new buildings a “concrete encased electrode” - one version of which is described by Scott - is required.
Excellent formation on surges and surge protection is in an IEEE guide at:
http://omegaps.com/Lightning%20Guide_FINALpublishedversion_May051.pdf
And a simpler NIST guide at:
http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf
An important point is to have a "single point ground" - entrance protectors for CATV, phone, ... be connected with a *short* wire to the conductor to the earth electrode at the power panel. With a large surge there will always be a difference from the house ground to ‘absolute’ ground. The goal is for the power and CATV and phone 'grounds' to rise together. Sometimes entry points are distant but a phone, ... wire can be run from its entry point to a 2nd protector adjacent to the power service and phone wires distributed from there. Or use a multiport plug-in suppressor. (For an illustration of the hazard see the IEEE guide pdf page 40.)
The NIST guide cites US insurance information that indicates equipment most likely to be damaged by lightning is computers with modem connection and TV related equipment - presumably with CATV connection. All can be damaged by surge voltage between signal and power, and a single point ground removes much of the risk.
That is also why signal wires must go through plug-in suppressors, as you indicated. All interconnected equipment must be connected to the same plug-in suppressor, or external wires must go through the suppressor. A plug–in suppressor clamps the voltage on all wires (signal and power) to the common ground at the suppressor. Mulitport suppressors are described in both guides.
And the final protective device that can be used is a surge suppressor at the power service. They are also described in both guides.
--
bud--
.
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- Driving a seperate ground rod
- From: Terry
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