On 3/21/14 6:28 AM, n8de@thepoint.net wrote:
I've been following this thread for a while and wonder why no one has
mentioned that a 'ground bar' is NOT a single-point ground.
Think of the 'ground bar' as a series-string of very low value RESISTORS.
Now ... think of your equipment as being connected to the 'nodes'
between each of those resistors ... rig A at one end, then rig B at the
first 'node' ... rig C at the second 'node' ... etc.
During a lightning strike, the huge voltage of the strike MIGHT appear
across that 'string' of resistors, causing each 'rig' to be at a
DIFFERENT potential.
POOF !!
I suggest that each piece of equipment have its own 'ground wire' and
those all be connected to a SINGLE point, perhaps at a point closest to
the ground rod. (Mine are all connected to a #0 wire going through the
wall to the ground rod about 7' from the 'single point'.
G
One hopes that the current is not flowing along your grounding bar. The
big reason for a bar along the back is that it's easy to connect wires
to it, rather than having a rats nest of longer wires all going to some
common point.
I doubt that in a typical "bench" or "table" scenario, that there is any
real difference in chassis potential between a "bus bar with short
stubs" and "radial grounding to a single point".
The big thing is to make sure that they're all bonded together, and that
that bonding is to something relevant to where the transient is coming
from.
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