I recently had to have the phone line replaced between the street
and the DeMark box on the side of my house.
It would have been a lot easier for the contractor to have
a new DeMark box on the side of the house and taken away the
old one ---- less tunnelling under driveways, etc.
I was told that the Demark box MUST be installed at the
service entrance and the ground wire attached to the service entrance
I suggested just putting in another ground rod at the alternate
location instead. I was told this was not allowed --- the Demark box
MUST go at the meter service entrance. Both the phone company
technician and the phone line subcontractor told me this, separately.
So, does anyone here have any expertise on this ? I'd sure like
see some discussion about this requirement.
Andy in Eureka, Texas
There is potential (no pun intended) to create a ground loop by using
two separate ground rods. Ground is somewhat of a relative term. Soil
composition and moisture content are two of the major elements that
can affect it. Not all earth grounds are equal.
ALL GROUNDS MUST BE UNIFIED!! Thats why the want the box by the
service entrance. seperate ground rods can create a different voltage
on grounded things, like during a lightning strike, that can be
thats why phone ground, is unified to main house ground rods, incoming
water line with meter jumper etc, even satellite dsh grounds should be
part of a unified system
Satellite dish grounds are for the sole purpose of dissipating static
electricity. There's nothing electrical about them.
That doesn't mean that some officious slug hasn't mandated that they be tied
to the central house ground, but I can't see that it would server any
All grounds must be connected together. While the dish ground is to
dissipate static and such, it still must be connected to the other ground
rods . Lets say it is not. If for some reason the other ground rod comes
loose from the house wiring and there is a short that should go to ground
and it doesn't , and you decide at that time to plug in the dish , you
complete the path to ground and get shocked or worse.
Also if a lightning strike is near the house it is possiable to develope a
big differance of potentional between the two ground.
On Wed, 27 Aug 2008 05:35:39 -0700 (PDT), " email@example.com"
Didn't my Ademco burglar alarm come with instructions to install a
separate ground rod? It's connected to the board and not the power
supply, I think to prevent induced voltages from lightning from
ruining the alarm.
It would have been a lot easier to just hook up to the electrical
ground, but I did what the instructions said.
It's been 25 years but I still have the instructions. I will check
It has been in the code for quite a while but buried out in seldom
read articles (Satellite and cable grounds were in the 800 articles
Things connected to the phone line were never really important until
people started buying phone equipment with 120v line cords on it
(modems, cordless phone or burglar alarms).
When they rewrote article 250 a couple cycles ago (the grounding
stuff) it got moved there.
I used to have a Comcast cable attached
to its own ground rod 30' or so from
the electrical service entrance. There
was a lightening strike on a street
the street behind me. It followed the
power cables to the underground area where
electrical, cable and telephone is for
my house. Because of the 2 different
we had lots of damage .... computer,
modem, router, scanner, garage door radio,
X10 stuff, and more. The Comcast guy
and the telephone guy all agreed the
should all be to a single point, the
electrical entrance. I know this is not
same thing, but working for the old Bell
System, we used single point grounds in
telephone offices to prevent lightening
from damaging the switching gear. I should
have seen this, but didn't until it was
Right on Art: Spent 40 years (1952 to 1992) in telecomm industry
Grounding is like a few other things you don't need very often .......
but when you do ..... !!!!!
Insurance policy, fire extinguisher, accident help, good neighbour
**Not Bell standard then!
Am very surprised. The various grounds are normally 'bonded' together.
In our case the power neutral is grounded as it enters the house and
has a ground rod. Also the TV cable service and the telephone
protector are grounded/bonded to the same ground. We have also taken
care to bond our ground to a buried copper wire loop that sits in the
trench above the now abandoned one inch plastic pipe to our unused
Many years ago our neighbour, had a bad leak to ground from his
electrical system. Since our systems were all bonded together we had
no problems; but he had some weird voltages floating around the
grounds in his house until he cleared the problem! It was a buried
entrance to his house that had 'gone bad'.
The soil resistivity here is high; so driving a single ground rod is
often not suitable. Hence most electrical systems now use MGN (Multi
Grounded Neutral). This means that except in the case of certain very
high voltage line guy wires everything that is 'ground' should be
bonded together and grounded. This includes overhead transformer
grounds, telephone and cable TV sheaths, pole line guy wires,
telephone sparklightning protectors etc. etc.
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