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Author Topic: Is that wire to outside gas meter a good ground  (Read 4531 times)
K7NHB
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Posts: 226




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« on: May 20, 2008, 09:53:21 AM »

I've read posts about the requirement to tie all grounds to the common power ground to prevent voltage differentials (ground loops?). But my main fuse box is in the wall in the garage and I don't see anything coming in or out of it (we have underground wiring in the neighborhood).

However, there is a fairly large twisted strand copper wire (once I scrape the paint off of it) going to the gas meter. I'm guessing that would take me to the "main" ground I am looking for.

Should I run all my connected grounds to that copper strand?

By "grounds" I mean various ground rods and the common rig "ground bus" coming out of the house to one of them.

Thank you and 73,
Paul
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W9LVM
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« Reply #1 on: May 20, 2008, 10:00:21 AM »

I have been a electrician for 38 years and would never ground any thing to a gas meter! Drive a ground rod outside house or two!
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WA3SKN
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Posts: 5523




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« Reply #2 on: May 20, 2008, 10:12:19 AM »

Unless you KNOW it is grounded, don't use it!
Anything coming from a gas meter would be suspect!
Let's not make things WORSE!
At the electric box there should be 220 Volts AC and a ground, or at least 110 volts and a common.  You can use a simple AC voltmeter to locate the ground connection... make sure you connect to that!

-Mike.

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AC5UP
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« Reply #3 on: May 20, 2008, 10:15:54 AM »

Let's suppose for a moment the gas line has been in the ground for a while and there is some corrosion in the pipe threads. Mechanically it may hold gas pressure OK Fine, but electrically?

By using the gas pipe as an RF ground shared with your breaker panel (and that doesn't sound like code to me, but who knows...) you run the risk of " lighting up " the whole house with RF if the Romex looks like a lower resistance path than the pipe.

Ditto the previous comment... Separate ground for the radio gear and don't be afraid of overbuilding or going too far in weatherproofing the ground system connections. A few hours and few dollars spent on grounding today can pay you back with years of no problems.
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K7NHB
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Posts: 226




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« Reply #4 on: May 20, 2008, 10:27:55 AM »

Okay - skip the thick wire on the gas pipe.

But the "connect all" argument that keeps popping up.

Someone says to drive a ground rod or two and I get that. But then someone else says that "code" requires ALL ground rods to be tied together (I have one at the base of each of two masts, and one outside the shack window) and connected to the electrical main.

I don't see an access to that electical main unless I can trust the center ground pin in a three prong outlet.

Even if I could disassemble the circuit breaker panel in the garage - getting to it with an outside wire would be problmatic.

So putting in a ground rod - no problem. Tying it to the main electrical ground - a problem.

Then I've read to just ground the Antenna tuner to a ground rod because the rigs all go through power supplies that have three prong plugs (this is a newer house, 1996, so I imagine the ground pin was done correctly.)
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K6AER
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« Reply #5 on: May 20, 2008, 11:23:09 AM »

All the gas lines I have seen are tarred and wrapped with polyvinyl tape and pretty well insulated. In addition they have a non conductive coupling at the gas main. This makes for a very poor earth connection.

Well casings also fall into the same category and present a very poor ground.

The reason the NEC requires all grounds to be bonded is to prevent ground surge potential. Should a lightning strike just outside the home or commercial residence the voltage potential from one ground will be higher than other grounds not bonded.
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N7UPI
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« Reply #6 on: May 20, 2008, 11:27:16 AM »

Do not connect your ground to th gas meter wire.  The wire you are seeing is used as a trace wire.  When gas companies lay the gas lines they are usually using plastic lines.  As they install the line, they also lay the trace wire with the pipe.  In order to locate the line, they will connect a signal generator to the wire and then trace the wire/line with a signal tracer.  
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WA3SKN
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« Reply #7 on: May 20, 2008, 11:30:06 AM »

If built in 1996 it should have a ground!
But, lets verify...
Break out an AC voltmeter.  At an AC outlet, you should measure voltage (120V) between the ground pin (round hole) and the hot lead (smaller hole).  You should read voltage between the Hot lead and the neutral lead (wide hole).  You SHOULD NOT see much voltage (less than 1 volt) between the neutral hole and the ground hole.
The breaker panel can be checked the same way.
And, you can check to see if that lead going to the Gas meter is grounded using the same technique!
VOM and DDM meters can be useful devices.

-Mike.
 
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KC9GUZ
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Posts: 164




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« Reply #8 on: May 20, 2008, 11:44:03 AM »

Outside wire to a gas meter??? NO!! Do you want to blow yourself up OM?Huh?
NEVER connect ANY ground wires or ANY wires to any thing that has gas in it!!!!
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K9JH
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Posts: 49




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« Reply #9 on: May 20, 2008, 12:28:53 PM »

I agree with N7UPI that it is a tracer wire, not a ground wire.  Do not hook anything up to it.
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WD8KDG
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Posts: 45




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« Reply #10 on: May 20, 2008, 04:24:47 PM »

Paul,

I see that you are located in Bend, OR. Last week the electrical service to my radio shack was upgraded, QTH is Springfield, OR.

So, since you are in Oregon, this state has not adopted all of the "NEC" word for word. Please check with the local electrical inspector for Bend. The inspector will inform you as what your grounding requirement are and might point out how & where the service grounding wire is connected to your panel in the garage. Shouldn't cost you a dime for his advise, and only his counts! The manuals for your radio equipment will or should instruct how it is to be connected to a proper ground.

As an example: Since my shack (separate frome the house) also has a telephone and TV cable run to it; two 5/8 inch diameter 8 foot ground rods were needed at the shack. At least 6 foot spacing between the rods was also required. #6 solid copper wire was used to connect the two rods together and to the subpanel in the shack. Where the state of OR differs with the "NEC" as I read it; the subpanel and main panel in the house are connected together with just #10 copper wire. Gotta please the local inspectors to get the holy water sprinkled and obtain blessings.

73's
wd8kdg
Craig
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KE4DRN
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Posts: 3734




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« Reply #11 on: May 20, 2008, 04:44:03 PM »

hi,

on my gas pipe there is a wire and a tag that
reads "cathodic protection" do not touch !

73 james
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K7NHB
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Posts: 226




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« Reply #12 on: May 20, 2008, 06:24:35 PM »

Okay - no worry about connecting to the twisted copper at the gas meter. From what N7UPI says - it is just a horizontal ground rod itself.  Besides, it's near gas.

WA3SKN, has given the expected results when testing the inside sockets. And WD8KDG mentioned that the electrical codes can be different from state to state.

If the only concern is potential difference during a lightening storm then this might be a non-issue. We get very few lightening occurrences here and when we do I can just disconnect the antennas or put the switch at "neutral".

I thought I had to bond all ground rods together (10-35 feet apart at the base of two masts and outside the shack window) and take it to the electrical main ground - which is nowhere to be seen. I'm sure, with out underground wiring, it comes up through the wall framing. That is, I don't see any power connection to the house with an "official" looking ground rod and heavy copper wire going to a fuse box or circuit breaker cabinet.
73,
Paul
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AK4QA
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Posts: 30




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« Reply #13 on: May 20, 2008, 08:46:58 PM »

There is a big difference between earth ground and RF ground.  They are not the same.
 
You are preventing a effect called a ground loop when you connect all the chassis grounds together, same length to same point.

This ground is not the same as the one you connect all your equipment too and run out to the window, THRU the metal barrier plate down to the ground rod at least 8 feet deep and as close to the house as you can get.

Also the reason you do not use gas mains is two fold.  First most gas companies are the only one allowed by code to use plastic pipe, and they do.  So what you think is a good ground connected to all the houses in the 'hood does not even go past your property line.

second, consider your pilot light in say, your hot water heater.  A ground spark runs in on the gas line and causes a by-pass flame.  Now you have fire on the OUTSIDE of your hot water heater.  Or stove, or furance...  

see my point?


Get the ARRL handbook.  READ the handbook.  Understand the handbook.


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K9KJM
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Posts: 2415




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« Reply #14 on: May 20, 2008, 10:22:43 PM »

I take serious issue with K6AER's statement that a well casing is "not a good ground"  RUBBISH!  A steel well casing encased in concrete for the top part is one of the very BEST grounds available!!!  In fact, Many commercial tower sites when on a location where 8 foot ground rods cannot be driven in because of close bedrock, Have a well drilled just FOR GROUNDING!

UL lightning protection standards call for all metalic objects to be bonded when within 6 feet of each other....... So if your ham radio grounds are more than 6 feet from your gas line, I would not attempt to bond to it. In fact, I would go to extra effort to avoid being within that 6 foot proximity....

IF it turns out that your garage electric subpanel is NOT properly grounded, You will need to bond it to your main panel (Which would be a good idea anyhow) Use #6 or heavier copper wire.
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