I understand that the NEC requires that all grounds (e.g., lightning
protection grounds and grounds for radio transmitting equipment) must be
bonded to each other and to the utility company's ground. The books I
have read say this is accomplished by connecting everything to the
ground "at the service entrance panel." But how is this to be
accomplished? By clamping the ground conductors to the conduit (after
cleaning it down to bare metal) that comes out of the ground and up to
the meter on the wall of the building? By bringing the ground conductors
through the wall of the building and into the panel and there connecting
them to the existing ground bus? Or . . . ?
I suggest you locate a Soars book on grounding. Probably the best
explanation to the industry. I also suggest that you start talking to the
local folks that do this sort of thing. Check around for the local
Independent Electrical Inspectors Association chapter or a Power Quality
Association in you area. Both are great people and are willing to help. I
belong to both, they have been a great source of increasing my intelligence.
Most folks take all of the grounds and tie the ground leads together on the
main grounding bus at the service entrance. Which can prove to be a problem
depending on the size of the ground bus. I have actually had to modify the
ground bus to allow for the size of wires that were needed.
I submit to you that you DO NOT want to tie an lightning protection to your
electrical service. Lightning protection is a sacrificial system. It dies
for the life of the building. All of the lightning systems (UL96A) I have
installed were grounded separately from the electrical service by at least
10 feet. I did a hospital that wanted the connections as you describe. When
I checked with the gas company they FREAKED. Letters came fast and furious.
No lightning protection connection to the gas line or no gas period.
The last computer building I did had 2 ground rings one for electrical stuff
and one for the lightning protection system, separated by 20 feet of earth.
The amount of energy that a single lightning bolt CAN deliver is sometimes
close to infinity for a fraction of a second.
I am a wizard, what I deal with is invisible. If you try to touch it; it
will kill you.
What about article 250.106? "The lightning protection system ground
shall be bonded to the building or structure grounding electrode system"
Nate, you are absolutely correct about Article 250.106. Further,
Section 3-14 of NFPA Standard 780, "Standard for the Installation of
Lightning Protection Systems", states: "All grounding media in or on a
structure shall be interconnected to provide a common ground
potential. This shall include lightning protection, electric service,
telephone and antenna system grounds, as well as underground metallic
piping systems." This section specifically states that
"Interconnection to a gas line shall be made in the customer's side of
the meter.", which may have been the source of excitement when the gas
utility inspected SQLit's installation.
You can ground to the meter enclosure, the service panel, the service
raceway (assuming it's metal), or anyplace you can get to the grounding
electrode conductor. I like using a split-bolt connector on the big bare
copper ground conductor where it comes out of the service panel.
In your case, I think I would use a ground clamp on the service raceway
outside the house by the meter. Or attach a big terminal lug on the meter
enclosure itself with a big (and short) sheet metal screw and lock washer.
I am asking for practical instruction how to ground my antenna tower
(when I erect it), etc. in accordance with the NEC.
On 02/15/04 06:04 pm Mark put fingers to keyboard and launched the
following message into cyberspace:
Ground rods are normally bonded by interconnecting them with #6 copper wire.
This may be one case
where using larger wire is not desireable -- use the #6 between the electrical
system ground and the
lightning type grounds, but perhaps use larger wires between any other
electrodes in the respective
systems. If the lightning system is permitted to use wires smaler than #6, then
I'd use the minimum
allowed wire between the two systems and consider a supplemental rod in the
lightning system and use
a larger wire like #4 or #2 to it.
Now that most of the snow has melted here in W. Michigan (although more
is forecast for tonight) and I have been able to get a better look at
the existing grounding arrangements, I have noticed that a heavy
stranded copper wire comes out of the ground alongside the conduit that
goes to the electricity meter; it then disappears between the slab and
the siding, so I assume that this is the ground connection to the ground
bus in the panel -- correct? If so, do I have to bring my separate
ground connection (from a radio installation, including a future antenna
tower) up into the panel, or can I simply bond it to that existing
accessible ground conductior outside the house?
The gas meter and telephone network interface are on the opposite end
wall of the house. The first thing I noticed is that an insulated wire
that comes out of the ground alongside the gas pipe is simply twisted
around it, with the bared end just "flapping in the breeze"; there are
no marks on the pipe to suggest that the wire was ever clamped to it.
Should I install a clamp myself, or should I call the gas company? (The
telephone interface box is just a few feet away from the gas meter, but
the wire that disappears into the ground from it has a different color
insualtion from the one wrapped around the gas pipe, so I don't think
the floating wire is supposed to be the ground for the telephone.)
But one other question comes to mind: can I really believe/assume that
these existing grounds are all connected together already? Is there
really a conductor running the 60ft or more from the gas meter and
telephone interface at one end of the house to the electricity meter at
the other end? How can I be sure?
Measure the AC voltage between them. Different grounds differ by some part
of a volt (AC). That's a one-way test, to tell they're
definitely not connected if you see voltage.
I get a half volt (AC) just between a couple of ground stakes driven into
the yard, anyway. If lightning hit nearby, it would be thousands, which is why
don't want two unbonded grounds inside the house together.
Set the meter on AC not DC. The voltage you see is from power grid grounds
reconciling themselves in the earth so it's AC too.
(Minnie Bannister) writes:
| The gas meter and telephone network interface are on the opposite end
| wall of the house. The first thing I noticed is that an insulated wire
| that comes out of the ground alongside the gas pipe is simply twisted
| around it, with the bared end just "flapping in the breeze"; there are
| no marks on the pipe to suggest that the wire was ever clamped to it.
That sounds like a tracer wire, not a ground.
| Should I install a clamp myself, or should I call the gas company?
I wouldn't make any changes without asking the gas supplier.
| But one other question comes to mind: can I really believe/assume that
| these existing grounds are all connected together already?
I wouldn't assume that they are connected. The professionals from the
telephone companies (and from the cable companies) sometimes skimp in this
area, and there is rarely an inspection to catch them.
Basically, yes, in this case, you should connect to the grounding system
outside the house. However if you have an overhead electric service you
should locate the antenna/tower as far away from it as you can. For a roof
mounted antenna the ground wire should go from the antenna (line of sight)
straight down to an antenna discharge unit then straight into a ground rod
driven far enough away from the house so that it is outside the roof drip
line. That ground rod should then be bonded to the main electric service
grounding electrode system using preferably, a #4 bare copper conductor.
Also, if you have an underground metal water supply line, it's very
important that you have have an unbroken (preferably #4) bare copper wire
connected from within 5 feet of where the supply line comes into the house
routed to the main electric service. Jumper across the water meter if
applicable, and jumper from the hot to cold at the water heater, if metal
pipes. Any sections of metal pipe that may have been replaced with plastic
pipe should be jumpered also. Use UL listed/approved ground
clamps/connectors, preferably bronze.
That doesn't sound good. A grounding connection should _never_ be made to
an _underground_ gas line. However, any _interior_ metal gas line should be
bonded to the main electric service grounding system. Local codes may vary.
Completely remove any kind of grounding connections to the outside and/or
underground gas lines. To be safe you should shut down your main electric
service before working with the grounding system.
That doesn't sound good either. There's a possibility that the telephone
interface box is grounded to the underground gas line. You'll want to
carefully dig that wire out until you find where is goes. If you are lucky
that phone ground wire goes to a ground rod that is installed as far away
from the gas line as practical, then that ground rod should be connected to
the main electric service ground on the other side of the house, again,
preferably with a bare #4 conductor.
I seriously doubt it, but there should be.
Carefully dig until you see where the wire is connected. See above.
The wire coming out of the meter and into the ground is probably the best
place to connect in your case. Most times the grounding connections are
made inside the main service panel on the neutral busbar and the neutral
busbar is then bonded to the panel enclosure.
On 02/23/04 04:01 pm volts500 put fingers to keyboard and launched the
following message into cyberspace:
No sign of any wire between the water pipe at any point and the
electrical system ground, and no sign of connection between hot and cold
pipes. Yet I did measure a low resistance (< 1 Ohm) between the pipes on
either side of the water meter (despite the Teflon-taped joints),
between the hot and cold water pipes (after all, they are both conencted
to the water heater), and between the water pipes and the case of the
No sign of a connection between the gas line and the electrical
grounding system either. But the gas line is connected to the water
heater, which is connected to the water line, which appears to have a
low-resistance connection (somehow -- see above) to the electrical
I found where the wire from the telephone network interface box goes: it
is connected to a cold water pipe inside the house, which is ultimately
conected to the incoming water supply -- all copper piping, except for
the sprinkler system.
How recent is the requirement that all grounds must be bonded together?
This house is 30 yrs old.
Years ago, when metal water pipes were used, it was permissible to use the
interior metal cold water pipe as part of the grounding electrode conductor
(not any more). Look for a cold water pipe that is close to the electric
panel, as you may find the connection there that goes from the water pipe to
the panel. One should not depend upon the pipe connections at the water
heater for bonding purposes, use jumpers.
You should try to determine if your underground water supply pipe is metal
or plastic. If it's metal, it needs to be connected to the main electric
service, no exceptions. It may be plastic since you seem to have a ground
wire that comes out of the meter, to a ground rod, then to the panel. If
the water supply line is plastic, you definitely need to bond the interior
metal water pipes to the electric service.
I think Dan clarified that that wire may be a tracer wire for locating
purposes, and of course,the gas supply line would be plastic then.
That would be a good place to bond all three together. If your underground
water supply line is plastic, you could then run a ground wire from the cold
water pipe nearest the panel, to the panel, which would then bond the hot,
cold, and inside gas line to the electric service.
The wire from the telephone interface should be less than 20 ft. What you
describe was permitted 30 years ago and would be grandfathered in. Since
plastic pipe became popular, the connection is now required to be connected
to the underground metal water pipe within 5 ft. of where the water pipe
enters the building. Or connect it to the (GEC) Grounding Electrode
Conductor (the one coming out of the electric meter.) If the ground wire
off the telephone interface were longer than 20 ft. (on a new install) then
you'd have to drive a ground rod at the interface and bond that ground rod
to the GEC. You should be OK the way it is now since yourinterior metal
water lines are intact.
If you have cable TV, it needs to be bonded to the electric grounding system
It's not a recent requirement, can't put a date on it though.
Earthing for two separate reasons. First for human safety
which is what the National Electrical Code (NEC) addresses.
All safety grounds long ago have to be bonded together. In
days past, the typically was to city water pipe where it
entered earth or, if using well water, to a dedicated earth
ground rod. In the past decade, earthing via a water pipe is
not acceptable no matter what that water pipe currently is -
copper or plastic.
Code since 1990 demands a dedicated single point ground at
the service entrance which means where AC electric enters
building. Telephone, CATV, satellite dish and even exterior
TV antenna should make a connection to this ground (either by
hardwire or via a protector). Code demands services such as
phone make a less than 20 foot connection.
Ground wires to pipes are for human safety - only to remove
electricity from those pipes. IOW wire once connected to city
water as an earth ground is now only to remove any electricity
that might leak into those pipes. Also required would be a
connection from hot water to cold water pipes at water heater
if pipes are metal; so that heater does not become part of the
grounding circuit. Water meter must also be bypassed so that
when water meter is replaced, then cold water pipes remain
connected to safety ground (meter man is not electrocuted when
Any connection to a pipe for grounding or earthing (ie a
cable connected to exterior water faucet) is not legal. Again
connections made to pipes only to remove electricity.
Ground to gas pipe is really a domain of the local gas
company. Some want gas line bonded to AC electric so that
electricity is removed from gas pipe - so that gas pipe will
not be used as an electrical path to earth. In one location,
neutral wire on transformer failed. AC electric then used gas
line as a path back to transformer via earth. This
unacceptable ground path eventually caused gaskets on gas
meter to break down; house exploded. But again, that safety
ground to gas pipe is according to local gas authorities.
Exterior gas line has a wire that is not an earthing wire.
All pipes have a wire so that radio signals can be transmitted
through pipe. This is how underground utility pipes and wires
are located - radio waves. That wire on incoming gas line is
how the locator service puts a radio wave on that plastic gas
pipe. Wire is not for earthing.
A meter typically cannot report a good ground; meter can
only report a defective ground. A ground that measures good
may simply vaporize - is too small - when it must conduct
larger currents due to an electric power fault. Meter would
not detect an insufficient ground. No replacement for visual
inspection. Furthermore, connections must be intended by the
designer to conduct electricity. A water heater was not
typically intended to connect hot water pipe to cold water
pipe. No matter what meter says, those two pipes still must
be bonded at that water heater (if metallic pipes).
volts500 wrote a good summary of bonding for human safety:
alt.home.repair entitled "Grounding Rod Info" on 12 July
That covers safety grounds as required by NEC. Now second
reason is to enhance earthing for transistor protection.
Those safety grounds were defined by wire resistance.
Transient protection is about wire impedance. That means
connections to that single point ground must be short, direct,
and independent. No splices, no sharp bends, less than 10
foot connection from incoming utility to that single point
earth ground, and not inside metallic conduits or pipes. Phone
line connects directly to earth ground rod - not to AC power
earthing wire. IOW every earth ground wire must meet at same
single point location and should route separated from other
non-earthing wires. (non-earthing wire can suffer induced
surges if bundled with an earthing wire.) This technical note
demonstrates principles of earthing a tower and building:
Building and tower are handled as if separate structures.
Each has it own single point earth ground. Any wire entering
each structure first connects to single point ground either by
direct connection or via components even sold by erico.com -
and others. Single point earthing for both structures is
interconnected by buried wire to enhance both earthings and
minimize potential differences.
One technique is to dig a shallow hole before driving
earthing rods. Buried wire connects each ground rod. A 4 or
6 inch plastic pipe placed in hole and backfilled so that
plastic cap can be removed to inspect wire bond to ground rod.
Size of buried interconnecting bare copper wire, depth of
that wire, and spacing between multiple rods are defined by
NEC guidelines. However, effective earthing materials (ie
ground rods) must be deep enough into earth where earthing
will not freeze. Frozen earth is not conductive - not a good
Minnie Bannister wrote:
On 02/24/04 01:53 am w_tom put fingers to keyboard and launched the
following message into cyberspace:
I am not sure what water pipe material is used outside the house. The
municpality was in the process of repairing or replacing the pipe from
the street to the house when we were looking at the house before buying
it. By the time we took possession everything was filled in again. There
is such a short length of pipe coming through the basement wall before
it connects to a brass or bronze fitting that I can't tell for sure, but
I think it's probably iron.
The telephone connection comes into the house at the opposite end from
the electric service entrance -- 60ft or more away -- so no way to
comply with the 20ft rule. The cable TV service (now used for Internet
only) enters at the back of the house, perhaps about 45ft from the
electric service entrance; there is a ground wire from the cable
company's box, but where it goes I have no idea. The satellite dish,
installed "professionally" about 3 months ago, is about the same
distance from the electric service entrance and with no sign of a ground
wire at all: the coax. cables come straight down from the dish and
through the wall of the house at a level just above the suspended
ceiling of the basement and, as far as I can tell, go straight to the
satellite box; if they do pass through a grounding block, I have no idea
to what that grounding block could be grounded.
The water meter is connected to two "arms" of a single brass or bronze
fitting in the line just after it enters the house, so there is a
permanent continuous electrical path even if the meter is removed.
But now if I want to ground the water pipe to the electrical supply
ground, can I run a wire to the ground bus in the panel located a few
feet away (in the laundry), or do I have to find a way of connecting
that wire to the ground at the service entrance panel (which has only
the main breaker and a breaker for the garage circuits) about 30ft away
on the garage wall? This would mean bringing the wire from the front of
the house (where the water line enters through the basement wall),
through the house (above the suspended ceiling of the basement), out
through the back wall, and around to the end of the garage where the
electrical service enters.
The water heater was replaced two years ago, according to the "seller's
declaration," but I have no idea whether it was done "professionally"
and in accordance with relevant codes. It will be easy to bond the two
pipes together; I assume that #4 is OK? Stranded or solid, or doesn't it
A lot of that I know in principle, but how to apply the principles to a
specific situation is not always obvious. E.g., when all these things
that are supposed to be bonded together are so far apart.
I like that idea, which I don't recall reading in any of the
One of the locals merely cut a groove in his yard with a power saw
(sacrificing a blade in the process, no doubt) and laid a ground wire in
that (but in conjuction with deep-driven rods, I think). Perhaps not
such a great idea?
Described is an earthing nightmare if intent is to also
protect household electronics. Does not matter, for example,
if CATV is only used for internet. Cable can still make a
destructive connection to other appliances. Things like
linoleum tile are electrical conductors where discussing
transients - meaning a house is full of other conductive
circuits. Once a destructive transient is inside the
building, then it will find many destructive paths to earth
ground. Best to earth is to a single point ground
Provided is one alternative to your bonding problem.
Looping the building (ie halo ground) makes earth beneath
equipotential. Connecting earthing for telephone, cable, and
AC electric to this loop helps make all part of a common bond
both for human safety and transistor safety:
It does not matter whether water pipe is currently metal or
plastic. The concept is siple. Water pipe, anyplace in the
earth, may at any time become plastic. Therefore water pipe,
today, is no longer acceptable as an earth ground. Code says
upgrade must use a dedicated earthing system. You don't care
whether a metal pipe section was replaced with plastic.
Assume it is or will be replaced by plastic.
They should have routed satellite dish wire to service
entrance to be earthed, less than 10 feet to the AC electric
earth ground. Only then does cable rise back up to enter
building. Recently, many cable companies are now just
starting to do this. Dish satellite installers cannot be
bothered; too much work. Apparently they get paid by the job;
meeting code is irrelevant. No help for you. But when that
cable enters building, it must, at minimum, connected right
there to an earth ground rod. Again, to bond that ground rod
to AC electric, see above pictures and concept from
cinergy.com . A halo ground solves many problems.
I thought you said the existing electric panel was bonded to
city water pipe? Why now are you asking how to bond to that
water pipe? Now I am confused based upon that last question
about grounding to pipe. Why ground to a pipe that was
already the household earth ground?
Minnie Bannister wrote:
On 02/25/04 01:25 am w_tom put fingers to keyboard and launched the
following message into cyberspace:
What are my chances of "leaning on" the installers and having them
rectify the situation? Can they legally be compelled to come back and do
Or what about running the cables through a grounding block at the
satellite box, then running the grounding wire back out through the wall
to a ground rod that will be connected to this halo ground (yet to be
installed)? Not grest, perhaps, but better than nothing, I guess. (And
what if the "halo ground" does not completely surround the building? How
would I get it across/under the driveway, for example?)
No. I am sure I said originally that there is no sign of a wire between
the water pipe and the electrical ground. I did say that I had measured
a low resistance (< 1 Ohm) between water pipe and electrical ground, but
I have no idea how that comes about; perhaps it is simply the resistance
of the wet (at the moment) earth with which they are both in contact?
On 02/25/04 08:49 am Minnie Bannister put fingers to keyboard and
launched the following message into cyberspace:
Or, now that I think about it further, it seems it would be much better
to run my own ground wire from the dish to a ground rod connected to the
And when I looked again at the diagram on the Cinergy Website, I saw
that it does depict a ground that goes only partway round the building.
I was confusing it with another diagram showing the ground wire going
all the way around the building.
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