"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Outdated only regarding water pipe Roy, but good advice.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

Jack Painter wrote:
Right Ian, having equipment spread out over a wide area is an
undesireable condition, but a reality for many operators. Running 3"
wide or greater copper strapping in individual paths to one single bus
"collector" is a challenge, but one worth trying. Equipment stacked or
racked together could certainly be "grouped" and a common bonding
strap run for each group to the SPG. But 20 linear feet of bus bar
could have huge transient voltages developed across it from a nearby
strike. As in a few hundred thousand volts between supposedly
"grounded' equipment. Hence the importance of all equipment connecting
to the same ground point, not via a long run of common bus bar to that
ground point. Make your compromises according to your individual
requirements and station layout.

Thanks very much for those thoughts, Jack.

As I'd guessed, you had some good suggestions, but you can see their
practical problems too. The same applies to an alternative method, which
is to group related items of equipment as closely as possible, and
connect them by the shortest possible straps to a large sheet of metal.

The key feature is that this sheet should be *very wide*, to create a
very low inductance and help minimize any voltage drops along its
length. Conductor thickness doesn't matter in this location, so a sheet
of copper-clad PC board is fine. It's also very easy to solder short
grounding straps onto the PC board, and move them around without having
to disconnect the whole sheet to drill it.

Some people put the sheet on the table, and the gear on top of the
sheet. If there is a shelf carrying another level of equipment above,
another practical way is to fasten the sheet to the underside of the
shelf.

The reason why conductor thickness doesn't matter in this location is
that we don't expect full-bore lightning surges through the station
itself. The ground bonding at the common service entrance should have
diverted the main surge safely to ground, so the equipment bonding
inside the station should only need to deal with very much smaller
currents - smaller, but still large enough to damage sensitive
electronics. Also, the higher-frequency components of the surge will
only run along the surface anyway, so what matters most is width and
surface area rather than thickness of copper.

As Jack says, busbars are a particular invitation to develop voltage
drops along their length. This "ground-sheet" system accepts there will
be some voltage drop along its length, but does everything practicable
to minimize it. A wide sheet is vastly better than busbars, and solid
copper busbars are a particular waste of money - a large sheet of scrap
PC board will do it far better, for almost nothing.

If I had the luxury of a large station, I'd use these sheets as part of
a wider-scale "grouping" system, as Jack suggests.


Just realize that in a nearby-by strike, lightning will find the weak
points in any system and exploit that weakness to the fullest
possibility.

In this climate, lightning is actually quite a minor hazard. What has
driven me to organize and bond equipment together is the need to control
RFI due to ground currents (of which I generate rather a lot). What's
good for the one is generally good for the other... and often good for
received noise reduction too.


--
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

"Wes Stewart" wrote in message
...
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

Should re read what I write sometimes. I was refering to using the water
pipe as the sole ground for your electrical system. This used to be a common
thing and pemissable by the NEC, not sure if it still is.

On Sat, 04 Sep 2004 20:28:58 GMT, "ku4yp" wrote:

i thank you all for the comments.

to tie into the electirical service will be a pain as the electrical
gound is on the total oposite end of the house from the shack. i'll have to
work something out there. water pipe grounding will not be a problem.

i can see i have much more reading to do.

thanks agian, mike

When we had an electrician upgrade the incoming electrical service box
on my mother's house (circa 1960), he ran a large 8 gauge wire from
the box at the end of the garage, along the wall of the house all the
way to the incoming water line from the street near the other end of
the basement, where he tied it to ground next to the water meter.

The National Electrical Code has changed, and those in older houses
might consider upgrading to current code (no pun intended) even if not
actually required.

In industrial situations, I have had to deal with ground loop
problems, which are a PITA to find. Do your grounding correctly, and
you will be safer, and have an easier time of it.

Happy trails,
Gary (net.yogi.bear)
------------------------------------------------
at the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom