I need some grounding-strap guidance, if'n you please

[ng3v]

Well, I guess I need some advice here as well.

I had not considered the problem of different grounds.  I am building a
house, now, where the electrical wiring will come in at one end of the house
while my radio room is 70 feet away, at the other end.  I had planned on a
separate grounding system at the radio room.

Would it be best to connect the two grounds?  If so, how would be the best
way to do that?

Or, should I have the electrical wiring come in at the same end of the house
as the radio room, thus eliminating "two separate grounds"?

Thanks,

Tom

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Ron D'Eau Claire
Sent: Tuesday, September 01, 2009 4:32 PM
To: 'Peter N. Spotts'; [hidden email]
Subject: Re: [Elecraft] I need some grounding-strap guidance, if'n you
please

Good story Pete, and a reminder that it doesn't take too many mA of current
to send you flying across the room (or into your grave). Even a bad ground
provides plenty of lethal current at mains voltage.

When I have a shop setup in a basement, garage or anywhere with a floor like
that I make sure the outlets are GFI protected. It's cheap insurance.

Over the past 30 years  we've moved back to the electrical equipment designs
of the 1940's and 50's in which safety is accomplished through insulation
rather than through a grounded enclosure. The fact that few modern tools or
appliances have 3 wire plugs testifies to this approach. Such equipment is
(apparently) very safe. (Safer than many of the old AC/DC radios, etc., of
the 40's and 50's  - especially after us young Hams unknowingly compromised
the insulation by taking a knob off exposing a bare control shaft or leaving
insulators out from under the chassis).

But the reliance on insulation rather than grounding for safety seems to be
bringing us back many unsafely grounded outlets. It's now very common to
have even brand new construction, signed off by all the appropriate
inspectors, turn up reversed wired outlets and missing grounds.

Ron AC7AC



-----Original Message-----
>
>snip<

Many thanks to all! My original question was prompted by an experience
I had as a teenager visiting my uncle in the mid 1960s (oops, the gray
hairs are showing). I was working in his garage, using a metal-housed
electric drill in bare feet on a dry concrete floor. (No cracks about
natural selection at work, please!).

I got a jolt about 2 volts shy of a hairstyle by Boston Edison!
(Although this was in a St. Louis suburb.) So that's what led me to
wonder if an anchor bolt embedded in concrete would constitute a
sufficient ground. It sure seemed to for that drill!

Thanks again for the helpful advice!

With best regards,

Pete


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[David Woolley (E.L)]

Rich wrote:

> trouble call for low voltage we found that both sides measured 120 VAC
> unloaded at the transformer and at the entrance box. with load it dropped a
> few volts with a heavy load it dropped about 5 volts. eventfully we
> discovered that there was a hidden break in the ground wire and the house
> was getting close to proper voltage with the lousy ground at the bottom of
> the pole and the house ground rod. Go Figure!  
>

This sort of fault condition is exactly why it is important that all
grounds be connected together within a building in the UK.  Modern urban
distribution systems use a system called Protective Multiple Earthing
(PME), in which the neutral (I think it was mis-named ground, above) is
grounded at multiple points on its path from the substation, but there
is no dedicated ground wire back to the substation, nor is there a
ground rod per property.

In this system, the building electrical ground is connected to the
neutral where the cable enters the property.

When the sort of fault described above occurs, there can be a
significant difference between the potential of the earth around the
property and the nearest grounding rod.  It may not be enough to
directly kill you, but even if not, the shock could precipitate a fall.


--
David Woolley
"we do not overly restrict the subject matter on the list, and we
encourage postings on a wide range of amateur radio related topics"
List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm>
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[Eric Swartz - WA6HHQ]

Guys - We're getting a flood of posts on this topic. Let's slow it down
a bit and end this thread by the end of today.
(0700 UTC)

73, Eric
Elecraft List Moderator

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[David Christ]

One final note on connecting grounds.  According to NEC the
grounding/protective ground (green) wire and the grounded/neutral
(white) wire are to be connected only at the main entrance panel.

In many cases where there is metal conduit, the conduit is used for
the grounding (green) system. To reduce noise sometimes a grounding
wire for each outlet is run all the way back to the point where the
grounding and grounded systems are bonded together.  As I recall,
generally these outlets are orange.

You can see this in action where there is more than one fuse box in
the house.  There is a green screw that connects the terminal block
for white wires to the box (which is grounded).  This screw is not
used in any of the sub boxes.

David K0LUM
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[Steve Ellington]

I've seen enough. There is no purpose in having a "station ground". In fact
it can be dangerous to have a ground system just for the station and one for
the electrical entrance. Think of the potential difference between those two
systems when lightning tickles one of them. Often the ground for the ham
shack is far better than the ground on your electrical panel. Guess where
the big surge is going to flow...Through your house then  righ through your
ham equipment! After all, your ham gear is plugged into the AC outlet. This
connects the two ground systems together....Not good!
Bonding all the ham gear together is a great idea but don't run it to a
separate ground rod. It serves no purpose. If you think this helps make your
signal stronger then think again...Sure a nice radial system will help that
vertical or random wire antenna BUT be sure you unhook it from your
equipment during a thunderstorm. All the ground rods in the world won't
protect your equipment from a strike and having it grounded to a ground
system AND to the AC mains is begging for trouble.
As for grounding the antenna...That's a different matter. The antennas
should indeed be grounded when not in use AND disconnected from the
station...Totally. In fact, your ham gear should be connected to NOTHING
during a thunderstorm. If you have a big ground wire coming in from outside
to your station, put a large knife switch in series with it and open the
switch when the station is not in use.
Picture this.....Lighting hits power line, goes to electrical panel, sees
wimpy old rusty ground rod and says "shucks there might be something better
here", travels through your AC house wiring, gets to ham shack, sees your
super duper ground system with 2" wide copper and 8,000 ground rods and says
"whoopeee"!!!,,,Goes to AC power cord on DC power supply, then to DC lead
from your new K3....through K3 to ground post on back of K3....to your
wonderful ground system and frys everything along the way. No more K3! Same
goes for your computer and everything else hooked to that nice ground. It's
all toast.
The same goes for lightning hitting your antenna....Even if you disconnect
the antenna with a coax switch, the shield is still connected right on
through to your equipment and then to your ground system. Zap....no more
rig....   Unhook the antenna and ground it....Don't hook the ground to the
rig.
Now I can hear someone saying "Hey,,,,without a station ground you'll have
RFI all over the place". Well maybe so but don't blame it on a lack of
ground rods....Usually the station's ground wire is some multiple of a
wavelength and makes a very poor RF ground anyway. If a ground system
happens to cure your RFI problems it's probably because it just happened to
resonate near your operating frequency. What you should do is try to
maintain a balanced antenna system and avoid common mode currents. Try using
a line-isolator in series with your coax etc etc.
Sorry I used so many words to say something so simple!

Steve
N4LQ
[hidden email]
----- Original Message -----
From: "NG3V" <[hidden email]>
To: "'Ron D'Eau Claire'" <[hidden email]>; "'Peter N. Spotts'"
<[hidden email]>; <[hidden email]>
Sent: Tuesday, September 01, 2009 5:01 PM
Subject: Re: [Elecraft] I need some grounding-strap guidance, if'n you
please

> Well, I guess I need some advice here as well.
>
> I had not considered the problem of different grounds.  I am building a
> house, now, where the electrical wiring will come in at one end of the
> house
> while my radio room is 70 feet away, at the other end.  I had planned on a
> separate grounding system at the radio room.
>
> Would it be best to connect the two grounds?  If so, how would be the best
> way to do that?
>
> Or, should I have the electrical wiring come in at the same end of the
> house
> as the radio room, thus eliminating "two separate grounds"?
>
> Thanks,
>
> Tom
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Ron D'Eau Claire
> Sent: Tuesday, September 01, 2009 4:32 PM
> To: 'Peter N. Spotts'; [hidden email]
> Subject: Re: [Elecraft] I need some grounding-strap guidance, if'n you
> please
>
> Good story Pete, and a reminder that it doesn't take too many mA of
> current
> to send you flying across the room (or into your grave). Even a bad ground
> provides plenty of lethal current at mains voltage.
>
> When I have a shop setup in a basement, garage or anywhere with a floor
> like
> that I make sure the outlets are GFI protected. It's cheap insurance.
>
> Over the past 30 years  we've moved back to the electrical equipment
> designs
> of the 1940's and 50's in which safety is accomplished through insulation
> rather than through a grounded enclosure. The fact that few modern tools
> or
> appliances have 3 wire plugs testifies to this approach. Such equipment is
> (apparently) very safe. (Safer than many of the old AC/DC radios, etc., of
> the 40's and 50's  - especially after us young Hams unknowingly
> compromised
> the insulation by taking a knob off exposing a bare control shaft or
> leaving
> insulators out from under the chassis).
>
> But the reliance on insulation rather than grounding for safety seems to
> be
> bringing us back many unsafely grounded outlets. It's now very common to
> have even brand new construction, signed off by all the appropriate
> inspectors, turn up reversed wired outlets and missing grounds.
>
> Ron AC7AC
>
>
>
> -----Original Message-----
>>
>>snip<
>
> Many thanks to all! My original question was prompted by an experience
> I had as a teenager visiting my uncle in the mid 1960s (oops, the gray
> hairs are showing). I was working in his garage, using a metal-housed
> electric drill in bare feet on a dry concrete floor. (No cracks about
> natural selection at work, please!).
>
> I got a jolt about 2 volts shy of a hairstyle by Boston Edison!
> (Although this was in a St. Louis suburb.) So that's what led me to
> wonder if an anchor bolt embedded in concrete would constitute a
> sufficient ground. It sure seemed to for that drill!
>
> Thanks again for the helpful advice!
>
> With best regards,
>
> Pete
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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[Bill Maddock-2]

David,

   As a correction, all conduits are to have a green grounding
conductor included per NEC. This was changed many years back in
thee NEC because it was found that conduit may not always
have a good ground all the way back to panel due to loose screws
corrosion etc.

73 de Bill N4ZI K3's #1059 & #2914

--- On Tue, 9/1/09, David Christ <[hidden email]> wrote:

> From: David Christ <[hidden email]>
> Subject: Re: [Elecraft] I need some grounding-strap guidance, if'n you please
> To: [hidden email]
> Date: Tuesday, September 1, 2009, 5:38 PM
> One final note on connecting
> grounds.  According to NEC the
> grounding/protective ground (green) wire and the
> grounded/neutral
> (white) wire are to be connected only at the main entrance
> panel.
>
> In many cases where there is metal conduit, the conduit is
> used for
> the grounding (green) system. To reduce noise sometimes a
> grounding
> wire for each outlet is run all the way back to the point
> where the
> grounding and grounded systems are bonded together. 
> As I recall,
> generally these outlets are orange.
>
> You can see this in action where there is more than one
> fuse box in
> the house.  There is a green screw that connects the
> terminal block
> for white wires to the box (which is grounded).  This
> screw is not
> used in any of the sub boxes.
>
> David K0LUM
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

     
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[Don Wilhelm-4]

Tom,

It is not only *best* to connect the two grounds, it is *required* by
electrical code.  If a knowledgeable electrical inspector should notice
the two unconnected grounds, he should properly fail the inspection.

I would recommend a perimeter copper ground wire (#6 or preferably #4)
all around the building - that is not hard to do in new construction.  
Put the wire 2 to 3 feet down and one to two feet away from the
foundation before the foundation is backfilled (hold the wire
temporarily in place with 6 inch long wire staples).
In addition to this wire, drive a ground rod (drive it, do not bury it)
at each corner or place where the wire must make a significant turn -
lightning likes to follow a straight path, so dissipate a bit of it in
the ground rod when the wire makes a turn.

The principle is that a lightning surge traveling through the earth will
tend to follow the wire rather than punching a hole through the foundation.

At whatever point along the path where the electrical mains ground rod
is placed, you can connect your perimeter wire to it.
Incidently, the best bonding of ground rods and grounding wires is a
CAD-WELD system and the whole thing can be below ground out of the way
of the lawn mower.  I have chosen to clamp mine, and the tops of the
ground rods are about 6 inches high, but I can periodically check all
the clamps for tightness.   I placed a loop of wire through the clamps,
so the perimeter loop is continuous.

73,
Don W3FPR

NG3V wrote:

> Well, I guess I need some advice here as well.
>
> I had not considered the problem of different grounds.  I am building a
> house, now, where the electrical wiring will come in at one end of the house
> while my radio room is 70 feet away, at the other end.  I had planned on a
> separate grounding system at the radio room.
>
> Would it be best to connect the two grounds?  If so, how would be the best
> way to do that?
>
> Or, should I have the electrical wiring come in at the same end of the house
> as the radio room, thus eliminating "two separate grounds"?
>
> Thanks,
>
> Tom
>  
>

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[Paul-285]

>But the reliance on insulation rather than grounding for safety seems to be
>bringing us back many unsafely grounded outlets. It's now very common to
>have even brand new construction, signed off by all the appropriate
>inspectors, turn up reversed wired outlets and missing grounds.

Electrician color code for receptacles:
"White on bright.
Black on brass.
Get em backwards and fry your ..... "
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