HeyBub wrote:
wrote:
Although you always want the cold water line BONDED to the grounding
system, it should never be THE ground. In fact, it does not meet code
for that use. For that you need a properly installed grounding rod at
the service entrance.
The purpose of attaching the electrical ground to a water pipe is not to
ground the electrical system, it's to ground the plumbing system.
I really don't understand where this nonsense comes from.
The NEC *requires* that a water service pipe, if it is at least 10 ft of
metal in the earth, be used as an earthing electrode. It has been a
requirement since 1777 (more or less). Also bonding is required across
the water meter.
Rules have changed somewhat, including now the connection to the water
service pipe must be within 5 feet of where the pipe enters the building.
For over 50 years the NEC has required a "supplemental" electrode for
water pipe electrodes *if* the water service pipe was likely to be
replaced by plastic. Years ago the code was changed to just routinely
require a "supplemental" electrode. Ground rods were routinely used. The
NEC requires the resistance to earth for a ground rod be 25 ohms or
less, or else 2 rods can be used. It is easiest to just install 2 rods.
Ground rods are a poor earthing electrode (25 ohms is slightly better
than nothing). A metal water service pipe is a good electrode,
particularly if connected to a metal municipal water system. The code
now requires, for most new construction, a "concrete encased electrode",
commonly called a Ufer ground, be an earthing electrode. This is a good
electrode, and replaces the ground rod(s) as a supplemental electrode
when needed.
Only if the water service pipe is not metal does the NEC require
*bonding* of the interior water pipe (instead of using the service pipe
as an earthing electrode). The rules are similar, but not identical, to
use as an earthing electrode.
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In addition to checking the earthing system, I would check the
neutral-ground bond, which should be at the service disconnect. If it is
not present, the hot and neutral wire potential could rise far above the
ground wire, which in some cases cause damage. The bond is often a screw
that looks like a mounting screw for the neutral bar. Recent ones are
likely green.
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bud--