US Calif here. Do the wiring regs require that Cable and Telco services are
bonded to the electricity ground. It seems that my telco has it's own
ground (a wire disappears into the earth!), and the catv service is bonded
to an electrical conduit (but not the the ground stake itself). Any advise
for getting them changed to comply with wiring regs at no cost?
Well, here in Illinois, they apparently want it all bonded to the
electrical ground. However, in my house, the cable is grounded to a
ground rod in the earth. An August lightning storm really messed up
things in my house. The best we can tell, the current came in through
the ground, hit the cable abd Malibu lights. It took out the cable
company's coupler on the pedestal. It took out my cable modem, router
and computer. I think the ground potential on the cable and the ground
potential on the electrical ground were very different (because they are
ground to different places) and thus fried everything in between. So if
you have lightning, it is probably important. If you are in southern CA
were there is little lightning, it is probably not that important.
Yes. Article 800 of the NEC (national electric code).
Good luck. The telco does whatever the hell it wants because they only
answer to the Public Utility Commision, and they know the PUC doesn't
care about residential grounding. The local electrical inspector also
has some jurisdiction, but he won't want to get involved. Perhaps he
has no real enforcement authority over the phone company? I went
through all this a couple of months ago. I ended up grounding the NID
myself, and I had to argue with the telco billing office for about 20
minutes when they tried to charge me for a service call when they sent
someone out who just told me "I checked with my supervisor and we don't
do that" and left.
BTW, bonding to the metal *service conduit* is specifically allowed by
the NEC and is about as good as bonding to the grounding electrode
system, so your CATV is likely OK.
I had a similar experience. I have a 625ft run of D.E.B. telephone
cable from their service box to my residence. I had several modems go
bad during thunderstorms so I called them to check the grounding. The
ground point was the service box and they would not drive a ground rod
at the residence. Case closed from their viewpoint. I drove my own
ground rod and connected it to their cable. Problem solved - no damage
for the last 2 years now.
Trust me the Telco did not drive an ground rod. They bonded to something
already there when they showed up. Maybe just lower on the riser. Which
could be bad for you if they removed the tape protecting the conduit.
Put an ohm meter on the wire for the Telco and the ground for the electrical
service or the catv ground. If it reads less than 5 ohms "forget about it."
If it is less than 25 ohms it might need some investigation. Over 25 start
Numbers sited are just educated guesses. Personally I have never
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com ).
Call 'em and ask. The NEC now mandates bonding to the electrical
service ground, but if your installation was before the change (1996?)
then the change won't happen until the line is serviced for some
reason. Locally, both cable and telco will do this anytime there
needs to be work on the connection, even if it's a test for fuzzy
This is far from a new change. It has been in the code since 1975 for sure,
800.13(b)(5) (the oldest book I have) and it was not new then.. The language
and location in the code may have moved around but the requirement that all
grounding electrodes on a premisis be bonded together has been consistant
| >The NEC now mandates bonding to the electrical
| >service ground, but if your installation was before the change (1996?)
| This is far from a new change. It has been in the code since 1975 for sure,
| 800.13(b)(5) (the oldest book I have) and it was not new then.. The language
| and location in the code may have moved around but the requirement that all
| grounding electrodes on a premisis be bonded together has been consistant
The thing that changed around 1996 was the ability to use the grounded metal
water pipe for the interconnection of grounding electrodes beyond a few feet
from the pipe's entrance to the building. Before the change you could drive
a local ground rod for your antenna or communications protector and connect
both the protector and the rod to any convenient grounded water pipe. After
the change you could still connect the antenna or communications protector to
any convenient grounded water pipe, but not if it had a local ground rod. The
local ground rod now requires its own #6 or larger bonding wire to the system
ground (e.g., another bonded grounding electrode, the EGC, etc.) much like any
other grounding electrode in the grounding system. Since this can mean
stringing a #6 wire half way around a house in some cases, the requirement
may act to discourage the use of an (otherwise good IMHO) local ground rod. :(
From some comments I've read here it appears that post-1999 code may no longer
allow the antenna or communications protector to be connected to any handy
grounded water pipe anymore (even if there is no local grounding rod). That
would put things back on an equal footing, though I suppose you are still
permitted to use thinner wire if there is no local ground rod.
You should know that the actual wire pair just isn't bonded to anything.
It does go through a protection network that would dump voltage surges to
ground but in normal operation neither wire is grounded. One of the two is
connected to "ground" via a coil at the central office and the other is
connected to -48 volt batter via another coil.
Most telephone lines enter underground and the cable is shielded. This
SHIELD is bonded to the electrical ground and for this reason, the network
protection box is placed within a foot or two of the electrical power
service. And the NEC and the utility rules call for connection to the
electrical service ground.
At the interconnection point between your house and the utility cable,
there are surge protectors that must be grounded, otherwise they are
useless against a high-voltage spike that comes in simultaneously on
The electrical code and FCC regulations require connection of this
ground terminal to the house's grounding electrode system, but the telco
ignores the rules because the local building inspector can't enforce
them and the public utility commission won't enforce them.
Been there, done that,
This is one of those cases where you can simply do it and stop worrying about
whether the telco/cableco is right or wrong. Buy a couple clamps and some 6 ga
solid and bond them. You can just call it a cheap insurance premium. The
utilities are certainly not going to pay you if your electronics all go up in
smoke during a thunderstorm because of a ground shift between the electrodes.
If you go back through the archives of the various electronics and home groups
you will see lots of arguments about surge protection but one thing that is
consistant between all of them is that you need a good single point grounding
Quite true. I guess I didn't make my point clear enough. Also, any
antenna grounding or lightning rod system is to be bonded to the power line
ground. Ditto for "cable TV" (that's the one that often isn't grounded.
Also, often the TV "dish" isn't bonding to the power ground. They all
should be bonded together.
They are going to be bonded together anyway. The problem is if you don't give
it a short, low impedance ground path at the electrodes the path is through
Most blown up PCs TVs and such is not because you had a surge. It is because
you had 2 surges, one on the power and one on the signal path. Any differences
got reconciled in the equipment where they meet.
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