In article <telecom24.307.9@telecom-digest.org>, Paul Coxwell
<paulcoxwell@tiscali.co.uk> wrote:
>> Article 250.54 of the NEC says local supplemental grounding
>> electrodes (such as the one for phone service) must be bonded to
>> the primary electrode. Where does the NEC apply? According to
>> what the telco man admitted seven years ago, I assume our county
>> code says the same thing.
> Which edition of the NEC are you looking at? In the 2002 edition
> article 250.54 relates to supplementary electrodes which MAY be
> bonded, not MUST. 250.58 does seem to correspond with 250.54 in
> earlier editions though, so that could be the section you are looking
> at.
> Chapter 8 of the NEC also relates specifically to communication systems.
> Article 800.40(D) in the 2002 edition states:
> QUOTE
> Bonding of Electrodes. A bonding jumper not smaller than 6 AWG copper
> or equivalent shall be connected between the communications grounding
> electrode and power grounding electrode system at the building or
> structure served where separate electrodes are used.
> /QUOTE
>> Is this a recent addition to the NEC?
> No. I don't know how far back the requirement goes, but the 1971 NEC
> says much the same thing in article 800-31(b)(7):
> QUOTE
> Bonding of Electrodes. A bond not smaller than No. 6 copper or
> equivalent shall be placed between the communication and power grounding
> electrodes where the requirements of (5) above result in the use of
> separate electrodes.
> /QUOTE
It looks like 800-31(b)(7) was added after 1965.
The 1965 code says, in section 800-31 (b)(5):
[QUOTE]
Electrode. The grounding conductor shall preferably be connected to a
water pipe electrode. Where a water pipe is not readily available and
the grounded conductor of the power service is connected to the water
pipe at the building, the protector grounding conductor may be
grounded to the power service conduit, service equipment enclosures,
or grounding conductor of the power service.
In the absence of a water pipe, connection may be made to a continuous
and extensive underground gas piping system, to an effectively
grounded metallic structure, or to a ground rod or pipe driven into
permanently damp earth. Steam or hot water pipes, or lightning rod
conductors shall not be employed as electrodes for protectors. A
driven rod or pipe used for grounding power circuits shall not be used
for grounding communication circuits unless the driven rod or pipe is
connected to the grounded conductor of a multigrounded neutral power
system. The requirements for separate made electrodes for power and
lighting system grounds, those for communication systems, and those
for a lightning rod installation shall not prohibit the bonding
together of all such made electrodes. See Section 250-86.
[ It is recommended that all separate electrodes be bonded together to
limit potential differences between them ans between their associated
wiring systems. ]
[/QUOTE]
> Disclaimer: Being British I'm just an outside observer to the NEC. I
> could post your query in a Stateside electrical forum where we have
> some NEC experts though, if you wish.>
> - Paul
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