w_tom wrote:
Old (older than every poster here) demanded the phone to be earthed
to a water pipe. That is no longer acceptable. Phone must now be
earthed to an electrode also used by cable TV and AC electric. Code
also says that wire must be 12 AWG. Most use 10 AWG wire. Code also
says that earthing wire must be short. That required to meet 'human
safety' code. For transistor safety, that wire from demarc (NID) must
be 'less than 10 feet', separated from all other non-earthing wires, no
sharp bends, no splices, not inside any metallic conduit, and should be
as short as practicable. These include post 1990 code requirements.

Same rules also apply to cable TV and AC mains earthing wire. All
earthing wires should remain separated until all meet at their common
earthing electrode.

Good information except the IEEE guide on surges and surge protection at:
http://www.mikeholt.com/files/PDF/Li...ion_May051.pdf
(guide page 28-29) recommends the NID (and cable protector block) be
mounted close to the electrical service, and their ground wire be
connected to the grounding electrode conductor from the electrical
service close to the panel. With high surge currents there will be
significant voltage drop on the wire to the grounding electrode (the
wire will have a much higher impedance at lightning frequencies than its
DC resistance). With separate wires to the grounding electrode, that
voltage will appear between the power wires and the telephone wires and
may damage equipment connected to both. When the NID is connected with a
short path to the power system neutral-ground bond, the phone and power
wires will rise together.

Old practice often connected the NID ground wire to a nearby water pipe.
When electronics is connected to both power and telephone wires that can
produce failures. I moved mine to the grounding electrode conductor (but
now I will be looking for thugs - thanks Jim). The NEC now allows
connection to water pipes only within 5 feet of the entrance to the
building.

--
bud--


If it does not exist, you should install the
earthing rod (for AC electric) before the telco comes out. You want
them to use your 'better' earthing. Else they may install one that is
insufficient (too short).

Only other ground for telephone wire is where that wire enters the
telco's CO. However AC electric must be earthed at your earthing
electrode AND at utility's transformer.

While inspecting, also confirm a safety ground wire from breaker box
to water pipe is still connected. Best attached at a point where water
pipe just enters the building and so that an earthing connection does
not pass through any soldered connections. Your gas company may also
demand same connection to gas pipe; a requirement that varies with
natural gas companies.

Most important reason to confirm ground wires and to route them deep
enough so at to not be pierced by a nail - human safety. Do those
inspections while it remains convenient.