ku4yp wrote:
i have a question.

in reference to station grounding, i have read keep the grounding strap
as short as possible and not a multiple of a resonant length on the ham
bands. with that in mind, even if i ground pieces of equipment to individual
ground rods, won't the complete grounding system be long? in my mind i am
looking around the room and seeing a grounding system being at least 12 feet
long, if i go along the perimeter of the desks (which are in a "U" shape in
the room.

W1MCE replies:

I have used a 1/2 inch copper pipe mounted along the back edge of the
table[s] holding my station equipment.

The case of each piece of equipment is connected directly to the copper
pipe using 1 inch braided strap about 6 to 12 inches long depending on
equipment size. This pipe provides an equipotential plane for all my
equipment. [Another method would be to install a thin copper sheath on
top of your desk/tables and connect directly to it for the equipotential
plane.]

Now, how to connect the equipotential plane to brown dirt [earth] is the
next issue. You are correct that it is desirable to keep this
'non-resonant' on the bands you operate. There are two issues here that
need to be addressed. First, if you are close to the earth ground then a
simple #6 AWG wire to a ground rod is adequate. Second, if you are
higher than 1/4 wavelength at the highest frequency of interest use two
#6 AWG wires OF DIFFERENT LENGTHS, not harmonically related, connected
to the ground rod. The different lengths assure that the equivalent
connection is NOT RESONANT.

In very fortunate cases an additional station ground is not required!
Believe it or not! ... My station is located on the ground floor in the
family [my] TV room right under the electrical distribution panel. My
120 VAC line comes directly from the service entrance through about 3
feet of wire. The 240 VAC for my amplifier comes directly from the
service entrance through 4 feet of wire. The service box is 'earthed' by
a NEC compliant connection. My connections to the service box are
therefore very short.

A major point of caution is required. The NEC requires ONLY ONE ground
connection. Multiple ground connections introduce VERY SERIOUS ground
loops that may violate the NEC criteria. This opens a VERY LARGE loop
hole in your home owner's insurance policy. If you are adding a second
earth [ground] connection at your station use an isolation transformer
to break up the ground loops in the basic 120 VAC connection. Consult
with an electrician regarding your local and NEC codes.

It is noted that station grounding and antenna counterpoise construction
are two different things. I am not addressing the counterpoise issue.

Dave Shrader wrote:
. . .
A major point of caution is required. The NEC requires ONLY ONE ground
connection. Multiple ground connections introduce VERY SERIOUS ground
loops that may violate the NEC criteria. This opens a VERY LARGE loop
hole in your home owner's insurance policy. If you are adding a second
earth [ground] connection at your station use an isolation transformer
to break up the ground loops in the basic 120 VAC connection. Consult
with an electrician regarding your local and NEC codes.
. . .

My NEC book is getting pretty old now, 1990, but at that time, multiple
grounds were often not only permitted, but required. And a *minimum*
spacing was sometimes specified.

For example, section 250-84, Resistance of Made Electrodes: "A single
electrode consisting of a rod, pipe, or plate which does not have a
resistance to ground of 25 ohms or less shall be augmented by one
additional electrode of any of the types specified in Sections 250-81 or
250-83. Where multiple rod, pipe, or plate electrodes are installed to
meet the requirements of this section, they shall be not less than 6
feet (1.83m) apart."

Or section 250-81(a), Metal Underground Water Pipe: ". . .A metal
underground water pipe shall be supplemented by an additional electrode
of a type specified in Section 250-81 or in Section 250-83. The
supplemental electrode shall be permitted to be bonded to the grounding
electrode conductor, the grounded service-entrance conductor, the
grounded service raceway, any grounded sevice enclosure, or the interior
metal water piping at any convenient point."

When I replaced the service (in 1979) in my 1952 house, the system
ground was a water pipe connection and I was required to add a ground
rod. Neither was considered adequate in itself; both were required by
the code at that time.

I agree wholeheartedly about consulting an electrician. Non-electricians
(including me) often have mistaken ideas about the content of the NEC.
It doesn't hurt to have an up to date copy of the NEC for reference,
either, if you anticipate doing any of the work yourself.

Roy Lewallen, W7EL

"Roy Lewallen" wrote

Dave Shrader wrote:
. . .
A major point of caution is required. The NEC requires ONLY ONE ground
connection. Multiple ground connections introduce VERY SERIOUS ground
loops that may violate the NEC criteria. This opens a VERY LARGE loop
hole in your home owner's insurance policy. If you are adding a second
earth [ground] connection at your station use an isolation transformer
to break up the ground loops in the basic 120 VAC connection. Consult
with an electrician regarding your local and NEC codes.
. . .

My NEC book is getting pretty old now, 1990, but at that time, multiple
grounds were often not only permitted, but required. And a *minimum*
spacing was sometimes specified.

Outdated only regarding water pipe Roy, but good advice. And Dave's above
interpretation of NEC is a misunderstanding of the subject - easy to do so
consult a professional if you have any douvbt whatsoever about what your are
doing. Isolation transformers are not an option for isolating a station
ground from AC service entrance. They are permitted only in lmited cases
where independent grounding is required, and in other cases where HV
isolating transformers or fiber optic isolate feedlines. No one in this
group will likely have that requirement, so put that out of your mind Dave.
You *MUST* bond your station ground to the AC service main ground. Ignore
this at the peril of your entire system, which had better be 100% isolated
from all power and external feedlines and grounds. That is an option for
protection, isolating from *everything*. But it means unplugging and
shorting to ground all feedlines, disconnecting and removing RF ground
connections, disconnecting computer modems, telephone, and AC power to all
of your connected equipment. A really poor option in my opinion, because if
you forget something, or risk your life trying to disconnect during a
surprise thunderstorm, what was it worth?


For example, section 250-84, Resistance of Made Electrodes: "A single
electrode consisting of a rod, pipe, or plate which does not have a
resistance to ground of 25 ohms or less shall be augmented by one
additional electrode of any of the types specified in Sections 250-81 or
250-83. Where multiple rod, pipe, or plate electrodes are installed to
meet the requirements of this section, they shall be not less than 6
feet (1.83m) apart."

Or section 250-81(a), Metal Underground Water Pipe: ". . .A metal
underground water pipe shall be supplemented by an additional electrode
of a type specified in Section 250-81 or in Section 250-83. The
supplemental electrode shall be permitted to be bonded to the grounding
electrode conductor, the grounded service-entrance conductor, the
grounded service raceway, any grounded sevice enclosure, or the interior
metal water piping at any convenient point."

When I replaced the service (in 1979) in my 1952 house, the system
ground was a water pipe connection and I was required to add a ground
rod. Neither was considered adequate in itself; both were required by
the code at that time.

I agree wholeheartedly about consulting an electrician. Non-electricians
(including me) often have mistaken ideas about the content of the NEC.
It doesn't hurt to have an up to date copy of the NEC for reference,
either, if you anticipate doing any of the work yourself.

Roy Lewallen, W7EL

Jack Painter
Virginia Beach VA

Roy Lewallen wrote:
Dave Shrader wrote:
. . .
A major point of caution is required. The NEC requires ONLY ONE
ground connection. Multiple ground connections introduce VERY SERIOUS
ground loops that may violate the NEC criteria. This opens a VERY
LARGE loop hole in your home owner's insurance policy. If you are
adding a second earth [ground] connection at your station use an
isolation transformer to break up the ground loops in the basic 120
VAC connection. Consult with an electrician regarding your local and NEC codes.
. . .

My NEC book is getting pretty old now, 1990, but at that time, multiple
grounds were often not only permitted, but required. And a *minimum*
spacing was sometimes specified.

For example, section 250-84, Resistance of Made Electrodes: "A single
electrode consisting of a rod, pipe, or plate which does not have a
resistance to ground of 25 ohms or less shall be augmented by one
additional electrode of any of the types specified in Sections 250-81
or 250-83. Where multiple rod, pipe, or plate electrodes are installed
to meet the requirements of this section, they shall be not less than 6
(1.83m) apart."

Is it something like this? Multiple ground rods are permitted
(encouraged, even) in order to establish one good ground connection; but
the wiring system can have only one ground connection.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ian White, G3SEK wrote:
Roy Lewallen wrote:

My NEC book is getting pretty old now, 1990, but at that time,
multiple grounds were often not only permitted, but required. And a
*minimum* spacing was sometimes specified.

For example, section 250-84, Resistance of Made Electrodes: "A single
electrode consisting of a rod, pipe, or plate which does not have a
resistance to ground of 25 ohms or less shall be augmented by one
additional electrode of any of the types specified in Sections 250-81
or 250-83. Where multiple rod, pipe, or plate electrodes are installed
to meet the requirements of this section, they shall be not less than
6 (1.83m) apart."


Is it something like this? Multiple ground rods are permitted
(encouraged, even) in order to establish one good ground connection; but
the wiring system can have only one ground connection.

Well, yes and no. As I read it, all the ground electrodes have to be
connected to the service box, as they are at my house. I have a
water-pipe ground and a ground rod; they're physically widely separated,
and each has its own conductor going back to the service box. So I guess
you could call the service box a single "ground connection". The neutral
and safety ground conductors of each circuit are individually grounded
at the service box also, giving further support to interpreting its
function as a single ground connection. A number of ground methods and
devices are approved, such as buried rods or plates, concrete grounds,
or (in my old code book anyway), water pipe ground. Some can be used
alone and others need a second ground device as a supplement. When
multiple ground rods are used, the code has requirements for bonding
them to each other.

Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
...

Ian White, G3SEK wrote:
Roy Lewallen wrote:

My NEC book is getting pretty old now, 1990, but at that time,
multiple grounds were often not only permitted, but required. And a
*minimum* spacing was sometimes specified.

For example, section 250-84, Resistance of Made Electrodes: "A single
electrode consisting of a rod, pipe, or plate which does not have a
resistance to ground of 25 ohms or less shall be augmented by one
additional electrode of any of the types specified in Sections 250-81
or 250-83. Where multiple rod, pipe, or plate electrodes are installed
to meet the requirements of this section, they shall be not less than
6 (1.83m) apart."


Is it something like this? Multiple ground rods are permitted
(encouraged, even) in order to establish one good ground connection; but
the wiring system can have only one ground connection.

Well, yes and no. As I read it, all the ground electrodes have to be
connected to the service box, as they are at my house. I have a
water-pipe ground and a ground rod; they're physically widely separated,
and each has its own conductor going back to the service box. So I guess
you could call the service box a single "ground connection". The neutral
and safety ground conductors of each circuit are individually grounded
at the service box also, giving further support to interpreting its
function as a single ground connection. A number of ground methods and
devices are approved, such as buried rods or plates, concrete grounds,
or (in my old code book anyway), water pipe ground. Some can be used
alone and others need a second ground device as a supplement. When
multiple ground rods are used, the code has requirements for bonding
them to each other.

Roy Lewallen, W7EL
Using a cold water pipe is a bad idea and is not allowed by some local codes
even though it may be allowed by the national code. This is partly because
it should only be connected to the ground system at one point and it is too
easy to connect it at more than one. Also there is the possible interaction
with gas lines and plumbers and home owners sometimes modify plumbing in
ways that make them poor grounds..

Jimmy wrote:
"Using a cold water pipe is a bad idea and is not allowed by some local
codes even though it may be allowed by the national code."

You don`t want to be electrocuted when holding an electric appliance and
a cold water valve simultaneously.

My electric company, the former Houston Lighting and Power Company,
writes:
"All services shall be properly grounded. Note - NEC requires grounding
to a "metallic underground water piping system" if available. Acceptable
alternatives include a driven ground rod which is preferred by HL&P Co.
regardless of the type grounding electrode used. NEC requires that the
"interior cold water pipimg system" be bonded to it."

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:

My electric company, the former Houston Lighting and Power Company,
writes:
"All services shall be properly grounded. Note - NEC requires grounding
to a "metallic underground water piping system" if available. Acceptable
alternatives include a driven ground rod which is preferred by HL&P Co.
regardless of the type grounding electrode used. NEC requires that the
"interior cold water pipimg system" be bonded to it."

That last point is the same in the UK. Gas and water supplies are never
relied on to provide an electrical ground, but they must be bonded to
the electrical supply ground.

Additional local bonding is also required for all metalwork in bathrooms
and shower rooms.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Wed, 8 Sep 2004 12:26:35 -0500, (Richard
Harrison) wrote:

|Jimmy wrote:
|"Using a cold water pipe is a bad idea and is not allowed by some local
|codes even though it may be allowed by the national code."
|
|You don`t want to be electrocuted when holding an electric appliance and
|a cold water valve simultaneously.

No kidding. I added a laundry room and attached garage to my house.
The former owner/builder had intentions to do something similar but
had not for whatever reason. He had stubbed out hot water from the
house (concrete slab on grade, pipes under slab) but not cold water.

I ran an exterior cold supply from the service entrance using PVC
underground and copper inside. I added another ground rod and 100' of
4 AWG buried at the base of the new footing and grounded the new cold
supply with it.

IMHO you can't have too many ground connections.
|
|My electric company, the former Houston Lighting and Power Company,
|writes:
|"All services shall be properly grounded. Note - NEC requires grounding
|to a "metallic underground water piping system" if available. Acceptable
|alternatives include a driven ground rod which is preferred by HL&P Co.
|regardless of the type grounding electrode used. NEC requires that the
|"interior cold water pipimg system" be bonded to it."
|
|Best regards, Richard Harrison, KB5WZI