NEC Section 810 Online?
 

I've not be able to find a copy of the NEC to read section 810 which
supposedly covers amateur antennas.

Anyone got a link?

tnx
jtm

"Jim Miller" wrote
I've not be able to find a copy of the NEC to read section 810 which
supposedly covers amateur antennas.

Anyone got a link?

tnx
jtm

Hi Jim,

The US National Electrical Code (NEC) is trademarked and copywrite property
of the National Fire Protection association (NFPA). There is no official web
posting of this information permitted. .

You may either purchase this information, visit your local library, or
request help from readers of this group who may subscribe to the NEC and
NFPA standards as I do. If you go to the library, also research Art 250
Grounding, and both 810 and 820. Various articles of the code are discussed
in various electrical forums such as Mike Holt, et al.

Best regards,

Jack Painter
Virginia Beach, Virginia

Hi Jack

I'll check out the library.

Not officially posting the information seems contrary to the aim of
ensuring adequate protection in these areas...

BWDIK...

jtm

Got to the library today and read 250, 800, 810 and 820. Interesting
section in 810 that effectively requires all Ham antennas to be 14AWG
or greater. Makes products like Wireman's 18AWG copperclad steel a
nonconforming wire for antennas.

I was planning to use the 18AWG for my 88ft center supported doublet.
The unsupported length would be about 50ft. The NEC is pretty coarse
grained at "anything less than 45meters".

Did I misread this? Makes "stealthy" antennas pretty difficult.

Section 250 is pretty opaque on grounding and bonding. I came away with
the impression that they wanted ground rods (8ft) every six feet. Did I
misread this as well?

tnx
jtm

"Jim Miller" wrote in message
oups.com...
Got to the library today and read 250, 800, 810 and 820. Interesting
section in 810 that effectively requires all Ham antennas to be 14AWG
or greater. Makes products like Wireman's 18AWG copperclad steel a
nonconforming wire for antennas.

I was planning to use the 18AWG for my 88ft center supported doublet.
The unsupported length would be about 50ft. The NEC is pretty coarse
grained at "anything less than 45meters".

Did I misread this? Makes "stealthy" antennas pretty difficult.

Jim, the NEC, in states that have adopted it, does not regulate low voltage
systems or antennas or comonents thereof, beyond (varying interpretations)
of the first bonded ground system. NFPA-780 Standard for the installation of
lightning protection systems DOES apply best practices beyond that point,
and yet it is not actually code. But it is referenced and for all practical
purposes, becomes code where referenced in NEC. Confused? ;-)

Your antenna may or may not be considered "low voltage" - this rarely if
ever comes up in construction permitting btw, but this group could debate it
for days. Your antenna system definitely becomes high voltage when afected
by a nearby or direct lightning strike. In my unqualified opinion, the two
reasons for minimum recommended wire gage, are withstand of high energy from
faults or lightning (fire and electrical shock hazard there), and durability
of external systems, the failure of which compromise parts or the whole of
electrical and lightning safety.

Most of the antenna language you collected are suggestions that are
interpreted as best practice. But they are not regulated and it probably
should omit comments such as you took somewhat out of context in your
example. Where NEC can be applied strictly (or not, again depending on your
state) is where antenna feedlines traverse inside spaces of dwelling,
commercial or industrial structures, and antennas attached to roof systems,
wall systems, interfaced with ground systems, etc. In those circumstances,
the possibility of death, serious injury, and severe property damage is a
real possibility where improper methods of construction would be allowed.
Minimum air-spacing in walls/attics is one example of that requirement.


Section 250 is pretty opaque on grounding and bonding. I came away with
the impression that they wanted ground rods (8ft) every six feet. Did I
misread this as well?

tnx
jtm


I think you did, yes. The relevant part of art.250 to comprehend, is the use
of bonding in both electrical safety and lightning protection. In electrical
safety, the purpose of bonding = fault clearing by low impedance path to the
circuit breaker, NEVER by providing a circuit path to earth and
earth-to-circuit breaker as the path to clear the fault. This is where 99%
of hams go astray, mostly because the daunted organizations of their
societies say grounding an amp, etc (to earth) will save their life. Wrong!
One radio engineer here, who I think is quite brilliant in those areas,
thought a ground-to-earth protected people, when in fact it could kill. This
is no doubt due to massive misinformation in the amateur world about basics
of electrical safety, as there is also about lightning protection.

Back to your ground rods - you should never modify or provide any electrical
grounding system for your high voltage AC system in a residence. Licensed
electricians are required for that. Your work will be related to grounding
and bonding an antenna system (including feedlines) to the mains electrical
grounding system, and that should be inspected but rarely is.

Your ground rods should be at least their sum's depth apart, and should be
sunk a minimum of 10' in the ground (or 3' deep if laid horizontally), or
the required number of feet in a UFER ground (bonded reinforcing rod in
poured concrete). 16' ("conductor" sum's depth of two 8' ground rods sunk
10' deep) is generally considered the separation standard you questioned. It
is described in great detail in NFPA-780.

I really applaud your actual work in the library on a subject too boring for
most radio enthusiasts to spend much time on, even though their very lives
(and others around them) could depend on it.

73,
Jack Painter
Virginia Beach, Virginia

Hi Jack

Thanks for the clarifications. The NEC 2002 book was a reference book
and required just sitting there and reading it rather than checking it
out. FWIW, there isn't much "context" on the antenna requirement other
than the blanket assertion of wire gauge vs unsupported span. I find it
interesting that 18th edition of the ARRL Antenna Book also references
this same NEC section then goes on to mention in another area of the
book how to use finer gauge wires to make stealthy antennas. Right hand
not knowing about the left hand???

As you noted I wouldn't dream of modifying the electrical ground system
of the mains of the house. I'm only going to put a little parade of
ground rods on the path to the mains ground rod and daisy chain them
all together with #2 with a pair of clamps on each rod. It will only
take two additional rods to get around the corner and up to the service
ground. I'll have to dig down to get to it I suppose.

There will be one ground rod out under the antenna feed drop in the
woods where the ICE unit will be directly mounted on the ground rod.
The tuner will also be located there after the arrestor.

From there the RG213 and control line from the tuner will run
underground about 60ft to the house where they will connect to the
shack ground rod just outside the window. The single point ground
inside the shack will drop out to this rod on about a 4ft run of copper
something. It's this ground rod that will connect to the other two and
finally to the service ground via the #2 daisy chain.

Coax (RG8x) is used to enter the house from the ground point so that
shouldn't be an issue per the code.

Since the antenna wire is actually out in the woods and 60ft or more
from the house I'm going ahead with the 18AWG copper-clad steel and not
worry about it.

I've got everything I need to finish this installation except the ICE
unit which is supposed to arrive today. Fingers crossed...

tnx
jtm

"Jim Miller" wrote
As you noted I wouldn't dream of modifying the electrical ground system
of the mains of the house. I'm only going to put a little parade of
ground rods on the path to the mains ground rod and daisy chain them
all together with #2 with a pair of clamps on each rod. It will only
take two additional rods to get around the corner and up to the service
ground. I'll have to dig down to get to it I suppose.

You should be good to go Jim. You might not have to scratch far to find the
AC mains grounding electrode. Depending on when your house was built, it
could even be a cold water pipe ground. If it is a rod, it is probably not
buried deep at all. The 10' rule is recent and not followed in most
residential cases anyway. When a local inspector arrives to approve a
contractor's installation, he is checking only for a 25ohm or less grounding
electrode. If the contractor cannot achieve 25 ohms or less from one
electrode, the code requires he sink a second electrode. And nothing else.
That's irony, huh?

Best regards,

Jack

Another question...

We have underground utilities in this neighborhood. The box on the side
of my house where the utility feed arrives has an approximately 1ft
section buried. There's actually a grade line marked on the side of the
box which I presume is a "do not exceed line. The service no doubt
enters through the bottom of this box.

I've dug carefully on one side of the box and so far haven't found a
ground rod. Before I continue digging I have a question about the
ground rod location.

Is it possible/typical that the contractor would put the ground rod
underneath the service entrance box in cases like these? If so it would
probably be pretty difficult to get to it.

Would driving another rod within a foot of the service panel be
adequate? (of course taking care not to penetrate the AC mains!)

I noticed the phone guy just put a hose clamp on the big metal
compression nut that has one side of the mains leading into the house
and put his ground under that. This is on the outside of the service
entrance box outside the house.

Would grounding through a similar compression bond to the box be a
reasonable alternative?

tnx
jtm

"Jim Miller" wrote
Another question...

We have underground utilities in this neighborhood. The box on the side
of my house where the utility feed arrives has an approximately 1ft
section buried. There's actually a grade line marked on the side of the
box which I presume is a "do not exceed line. The service no doubt
enters through the bottom of this box.

I've dug carefully on one side of the box and so far haven't found a
ground rod. Before I continue digging I have a question about the
ground rod location.

Is it possible/typical that the contractor would put the ground rod
underneath the service entrance box in cases like these? If so it would
probably be pretty difficult to get to it.

Would driving another rod within a foot of the service panel be
adequate? (of course taking care not to penetrate the AC mains!)

I noticed the phone guy just put a hose clamp on the big metal
compression nut that has one side of the mains leading into the house
and put his ground under that. This is on the outside of the service
entrance box outside the house.

Would grounding through a similar compression bond to the box be a
reasonable alternative?

tnx
jtm


Hi Jim,

The buried conduit casing of the AC mains entrance to your meter is most
likely NOT your house ground. The main AC breaker panel for your home,
whether that be in a garage or wherever (surely close to the meter though)
is where the house AC neutral wiring and house AC ground wiring all meets at
one bonding location. THAT is the source of the single point ground
conductor, which leaves your panel and finds the nearest approved earthing
connection. You may have to get under your house to see where that green
bonding jumper drops down from the panel, and penetrates the outside wall,
then connects via a bronze ground rod clamp to the home's single point
ground rod. Telephone and cable and all radio shield grounds MUST BOND to
this ground rod. It is probably just inches beneath finished grade, and
within a foot or so of your foundation wall, right outside the breaker
panel.

In the unlikely event that your builder actually used the aluminum casing of
buried conduit for his AC mains ground connection, then the telephone
company was proper in bonding to the same place. But if you have a buried
ground rod as 99% of residences do, then that is the ONLY place that all
utilities must ground to.

The reason it would be unlikely to have the conduit as a earthing ground
connection? Because the utility should inspect for a contractor installed
ground rod before they hook up. Using their buried conduit, while possibly
legal, would be unusual at best.

Hope this helps,

Jack

Hi Jack

Well I moved some stuff around in the basement and found the house
ground. It actually protrudes out of the concrete floor directly below
the two breaker panels. Each panel has what appears to be #4 solid
copper coming down to bronze clamps on this rod.

There's no ground outside at all which is why the Verizon guy chose to
ground to the Thomas and Betts meter cabinet that I mentioned which is
4ftx6"x15" or so and partially buried. Here in MD they just do direct
burial rather than use a conduit. The entry to the house panels from
the meter box is just via heavy cable, no conduit there either. The
Comcast guy just put a ground on the splitter and ran it a foot or so
to the closest circuit breaker panel.

So should I just drive one more rod pretty close to the box to finish
the daisy chain close, then go inside and bond to the single point
there? Seems crazy to take this inside... I'll have to drill a hole
through the sill plate on an angle then feed the wire up from my
proposed exterior ground rod, through the sill plate, then down the
inside of the concrete basement wall to where the other two grounds are
attached to the ground post.

tnx
jtm