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Author Topic: Bonding to the Electrical Service Ground  (Read 8405 times)
N8EUI
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« on: May 06, 2010, 05:26:17 AM »

Per the NEC code and all I've read here on this forum, I'm going to bond all my grounds to the electrical service ground so in the event of an induced rise in voltage due to say, a distant lightning strike, everything grounded will be at the same ground potential.  I've discovered however, that my electrical service ground is bonded to my copper water line inside my house in the basement.  Is it safe to bond all the grounds to an indoor electrical ground?  It doesn't seem safe to me.  In my research, I've learned that the electrical ground tends to be outside the structure.  Should I remove the indoor electrical ground and place it outside, bonding it to a ground rod?

Thanks,
Tom, N8EUI
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K9KJM
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« Reply #1 on: May 06, 2010, 10:18:50 PM »

No.  See other query.
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N8EKT
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« Reply #2 on: May 07, 2010, 12:31:31 PM »

Simply drive in an 8 foot ground rod and common it with the service reference.
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K1CJS
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« Reply #3 on: May 16, 2010, 03:23:04 PM »

If the 8 foot rod in your basement is driven into the floor, you're going to have a deeper ground rod installation, more likely to be at a better conductive (water table dependent) level.  Just bond your station ground to the rod in your basement.  A ground rod does NOT have to be outside.
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WX7G
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« Reply #4 on: May 16, 2010, 05:01:17 PM »

If you think you'd enjoy the excitment of having lightning current taking a path through the house wiring to the basement ground rod go ahead and install it.

Otherwise use a ground external to the house and bring the coax shield directly to the house AC power ground. Then there is no path for lighting current through the house wiring.
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K9KJM
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« Reply #5 on: May 16, 2010, 11:09:56 PM »

WX7G has a very good point.

Ground rods should NEVER be installed indoors!!!!!!!!!

Keep your ground rods outdoors.

Bonding all ground systems together NEEDS to be done.   Always run each system to it's own outdoor ground rod(s) first, Then bond the systems together.
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AA4PB
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« Reply #6 on: May 17, 2010, 06:25:23 AM »

"my electrical service ground is bonded to my copper water line inside my house in the basement"

Yes, per NEC the water line is bonded to the electrical service, but the electrical service should still have a ground rod outside. The NEC wants all grounds to be connected together to prevent a voltage difference between them that could prevent you from receiving a shock if you were to come in contact with two grounds.

Consider the case where your radio is connected to the unbonded antenna ground. Some other accessory has a metal case connected to the electrical ground via the third pin in the plug. You place one hand on the metal case (electrical ground) while you touch the radio (antenna ground) with the other. Any leakage current flows through your body. By making a low resistance connection between the two grounds you provide a path for this current other than you. Numerious times I've seen coax connectors "spark" when connecting them to the radio because the antenna and power grounds were not bonded properly.

In the case of the water pipe, think of someone with one hand on a hair dryer and the other on the water faucet.
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KI4SKM
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« Reply #7 on: May 17, 2010, 06:43:31 PM »

Sorry to be dense if the answer is obvious.

My antenna entrance is on the backside of our house. The electrical entrance is on the side. 50-60 feet approximately around the house. My question is about bonding the two together. I would have to go around one corner of the house, and through a 2" pvc pipe that runs under the concrete walkway to the electrical service entrance.

I'm not sure I understand how to handle this. As for the corner, I see "no sharp bends". How do I handle this?

Do I need to install several ground rods ≈16' apart along the path and tie the ground wire to each on the way to the electrical service ground? Thanks,

   ---Bill Tuttle <> KI4SKM

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WA9UAA
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« Reply #8 on: May 17, 2010, 07:31:44 PM »

Quote: Do I need to install several ground rods ≈16' apart along the path and tie the ground wire to each on the way to the electrical service ground?"

Bill,
This is what I did, otherwise my shack would have been in the downstairs loo. Roll Eyes
73,
Rob WA9UAA
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AA4PB
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« Reply #9 on: May 18, 2010, 05:53:21 AM »

Quote: Do I need to install several ground rods ≈16' apart along the path and tie the ground wire to each on the way to the electrical service ground?"

In terms of lightning protection this is the best way to do it - keep the bonding wire outside of the house.

In terms of NEC requirements (mostly for personnel safety), you could bond your antenna ground system to the copper water pipe provided the pipe is already bonded to the electrical system. The NEC doesn't state how or where the bonding wire is to be run so you often find cable and phone service grounds simply connected to an exposed metal water pipe. This is better than no bonding.

As for "sharp bends" just make a sweeping 90 degree turn (radius of 2-3 inches).


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WX7G
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« Reply #10 on: May 18, 2010, 07:55:24 AM »

Lightning protection is not just about a low impedance ground path but directing the path of the lighting current. This is why the best situation is where the coax shield is bonded to the electrical service GND by a zero length wire. The coax going to the rig and the AC power going to the rig maintain the same potential during a lightning strike. There is no other path to earth GND through the house wiring.

The better the lighting GND the lower potential the house wiring jumps to during a lightning strike.
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KI4SKM
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« Reply #11 on: May 18, 2010, 08:55:54 AM »

Thanks everyone, keep it coming. Smiley

My shack will be in the basement and the feedline can't come in by the electrical entrance. I also have a electrical sub-panel in the basement that I thought I could also bond the shack ground to. I had planned on bringing a ground in through the wall with the coax, and tie it to the sub-panel ground as well. Is that a bad idea?

   ---Bill Tuttle <> KI4SKM

« Last Edit: May 18, 2010, 02:37:27 PM by Bill Tuttle » Logged
K3GM
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« Reply #12 on: May 21, 2010, 09:18:07 AM »

.....Ground rods should NEVER be installed indoors!!!!!!!!!......

My house was built abt 9 years ago, and my service ground is technically "inside" my house.  It's in my under-house garage. If it were outside by the meter, it would be subjected to possible damage from snow removal equipment as the box is directly above my asphalt driveway apron.  My coax entrance panel and towers are tied to the service ground.  Although it would have been a much shorter run to go thru the basement from my shack to the garage, I took the long way around routing it outside, and actually drilled thru the 12" poured concrete wall to bring it back inside where it connects to the service wire by means of a Servit connector. Where it passes across the driveway apron and the 2 garage doors, I notched a small groove between the ashpalt driveway, and the concrete threshold of the garage, and pushed the wire in there covering it up afterwards.  You'd never know it's there except where it emerges from the asphalt and goes thru the wall.  My town's inspector is tough, and not being an electrician, I'm comfortable where the approved service ground is located.  If you're expecting to see a cartoonlike bulge in the wire or a visible flame as a transient spike "travels" down it, safe to say it doesn't happen that way.  Grin
« Last Edit: May 21, 2010, 09:20:17 AM by Tom Hybiske » Logged
KB1LKR
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« Reply #13 on: May 21, 2010, 02:15:34 PM »

Re: inside vs. outside electrical service bonding/grounding it appears (at least in the Northeast US)  the common practice at one time (perhaps up to as little as 15-20 years ago???) was to ground the primary residential electrical service entrance by running a 6 AWG (or larger) wire from the combined grounding/neurtal buss of the primary service entrance panel to the copper, underground water service line (ideally on the street side of the water meter, and if not then w/ a 6AWG or larger bonding cable around the water meter).

Somewhere along the line it appears the code requirements were changed and an exterior driven ground rod was installed below the electric meter socket and the neutral conductor grounded there (again 6 AWG min wire), in addition to bonding the cold water line to the ground/neutral buss of the primary service panel.

In either case, after the primary service panel the (grounded) neutral and the safety grounding conductors and busses remain forever separate (though both are at ground potential.) Well, at one time, this wasn't always true either -- electric ranges and dryers were once fed 240/120V via only 3 wire services (the crow's foot style plugs/receptacles) w/o a grounding conductor (only two hot lines and a neutral (for the 120V)). Often they'd be equipped w/ a strap to bond the (grounded) neutral to the frame of the appliance as an alternate to leaving them floating. Now 4 wire cords/plugs would be used, keeping the grounding conductor separated from the neutral.

Telephone, and more recently CATV services tend to be grounded/bonded to the nearest convenient metal water pipe by the installing utility, vs. the ideal of being bonded to the grounding rod/pipe/etc.

You could have an electrician (or the power utility?) update your service grounding to current code, moving the grounding point external to the structure.
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N8EUI
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« Reply #14 on: May 22, 2010, 08:05:22 PM »

Hello everyone,

So I had a larger service panel installed by my electrician last week.  He also drove two eight foot ground rods outside, next to the service entrance.  Now I have an outdoor grounded electrical service which is bonded to my copper water line in the basement.

According to AA4PB's reply on May 17th: "Yes, per NEC the water line is bonded to the electrical service, but the electrical service should still have a ground rod outside. The NEC wants all grounds to be connected together to prevent a voltage difference between them that could prevent you from receiving a shock if you were to come in contact with two grounds."

So, am I good to bond my station grounds to the outside ground rods which in turn are bonded to the inside copper water line with say, #4-6 solid copper wire?

Thanks again,

Tom, N8EUI
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