Tekkie® wrote:
N8N posted for all of us...

On Apr 30, 3:10 pm, westom wrote:

Is it possible to ask a simple question on AHR about surge protection
and/or grounding without...

...never mind. I know the answer to THAT question.

nate

(you'd think I'd learn. But I seriously would like to know if there's
any way to "verify" that a building ground is good without digging up
the ground rods.)

Such a simple question. You would think there would be a simple answer.

Easiest is probably follow the earthing conductor to find what
electrodes are used (as John suggested). A metal water service pipe is
an excellent electrode [but can invoke another of w's delusions]. In
older buildings the other electrode you may find is one or more ground
rods. Rods are not a particularly good electrode. It is probably easier
to add a rod than determine if an old rod is still good.

Measuring resistance to earth can be done with a 3 point tester - not
easy. There is a simple clamp on tester. Not likely you can borrow one.
A contractor may have one.

An old method I have read about is to disconnect the earthing conductor
from the service and connect it to the hot through a 6.25A fuse [a
standard size]. If the fuse blows fast the resistance is 20 ohms or
less. I might try this but I'm not sure I would recommend it - there are
a number of hazards including just disconnecting the wire. The earthing
wire must not contact *anything* but the electrode. (This also depends
on the earthing of the utility transformer and can result in some
earthing current through other customer's electrodes.)


Crossed power lines are rare and it is difficult to provide protection.

As I noted elsewhere, much of the protection from surges is actually
having the power and phone and cable wires stay at the same potential
(although elevated) during a surge event.


I believe a megger can be used.

A megger is to measure very high resistances (megohms, like insulation).

--
bud--