Re: How to ground electric outlets over a slab?
- From: westom <westom1@xxxxxxxxx>
- Date: Wed, 29 Apr 2009 21:39:44 -0700 (PDT)
On Apr 29, 8:31 am, N8N <njna...@xxxxxxxxxxx> wrote:
But that prompts a question - short of going outside and digging along
the ground cable and inspecting the number of buried ground rods, how
would one determine if an older house does in fact have proper
grounding? (I know, lift the neutral to the pole and see if anything
blows up...)
Ground must be installed so that it can be inspected. Visual
inspection is the only method to confirm an earth ground exists and is
sufficient. Furthermore, every incoming utility must make a short
connection to that same earthing electrode. IOW a gray NID telephone
box contains a 'whole house' protector that must be earthed. Cable TV
is earthed directly - no protector required. These ground wires
should be traced to the same ground rod that is also just outside the
breaker box.
Grounding serves two functions. First is human safety. Code states
what is required. Second function is surge protection. That means
grounding must exceed those requirements. Connection from each
utility wire (ie breaker box, telephone NID, cable ground block) must
be short (ie 'less than ten feet'). Separated from other wires.
Only meets all other ground wires at the same earth electrode. No
sharp bends. Not inside metallic conduit. Violation of any of these
means a ground for surge protection has been compromised.
Remember what a surge proetctor does. Diverts energy to be
harmlessly dissipated into earth. If ground via the safety ground
wire inside romex, well, that wire also violates most every above
requirement which is why 'point of use' protectors have no earthing.
Which is why 'point of use' protectors do not even claim to protect
from the type of surges that are typically destructive.
Sounds like your best solution is to install new grounds so that all
incoming utilities make that short connection to earth. Since a surge
protector is defined by quality of its earthing, then additional
earthing would make an effective protector even better.
Earthing must meet and exceed post 1990 code requirements to
accomplish what you are asking. Type of surge that typically destroys
appliances is either earthed (dissipated harmlessly in earth) before
entering a building. Or finds destructive paths through household
appliances inside the house. A protector connected to earth via
household wires (ie romex) is all but no earth ground. It may then
earth that surge destructively through an appliance as we have seen so
often. A surge diverted into and dissipated in earth need not enter a
building - does not overwhelm protection that already exists inside
every appliance.
.
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