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Author Topic: Can I Bond Directly to the AC Panel Ground Bus  (Read 6641 times)
KB1VCZ
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« on: April 14, 2011, 08:31:34 AM »

I live in a condo and my shack is setup right next to the AC service entrance. The panel is above my shack bench. There is a ground wire that runs to the panel from outside through conduit along with the AC main wire runs, but I have yet to locate that actual ground rod that connect to the panel.

In a perfect world, I would drive a ground rod into the ground just outside the shack wall and bond that to the AC system ground rod, and tie the station ground rod back to the shack SPG bar, which would be connected per code to the AC service ground.

I can't do that though.

So, I have two options:

1. Run a heavy guage wire (1.5 ft) form my SPG bus bar in the shack directly the the AC service ground bar in the panel box and leave it at that.

2. Drive a station ground rod into the ground and connect that to the AC service ground bar in the panel box with 2.5 ft run of heavy guage wire , then attach another 2.5 ft run of wire to the ground rod from the shack SPG bar.

Which would be preferable under my circumstance?

#2 seems like the best to me, but I would be interested in anyones comments or experience with this kind os a setup.

I also have a question about grounding my coax, but I'll hold off on that oen for now.
« Last Edit: April 14, 2011, 08:44:56 AM by KB1VCZ » Logged
W8JX
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« Reply #1 on: April 14, 2011, 09:39:58 AM »

Does condo have a steel or cooper pie supplying water to unit? You really want a separate ground of some type if possible.
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KB1VCZ
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« Reply #2 on: April 14, 2011, 10:14:16 AM »

Yes it does, and in fact I'm using the water pipe as my station "ground rod" currently. This solid pipe is also grounded to the AC panel ground bar per the NEC. The reason I posted my question is because I think I can do better with my setup, even with my constraints.

Today, I found the condo complex(4 units) ground rod which is at the meter box.

The distance from my unit to this rod is about 50ft - 60ft. It is located on the other side of the driveway with all wiring routed via underground conduit.

The only way i could bond to that rod with a station ground rod is to either splice into the ground wire inside the AC service junction box on the outside wall of my shack, or, run a wire directly to the ground bus bar in the AC panel (#2 in my first post) from the station ground rod.

Complicating all this further is that all my COAX runs come in from the exact opposite side of the condo (antennas on my deck) and there is no practical way to ground a bulk head plate, unless I drive a ground rod into the asphalt pavement. Even if I did that I would still have to bond that ground to the station ground rod and AC ground rod, which in my case is impossible.

This all leads me back to just establishing a safety ground for the shack equipment (either option #1, #2, or #3) with #3 being what I described above--outside station ground rod bonded via splice.

#3 seems like the best option, given that the "bonding" would occur outside the premise.


« Last Edit: April 14, 2011, 11:05:43 AM by KB1VCZ » Logged
W8JX
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« Reply #3 on: April 14, 2011, 05:02:22 PM »

I am not sure as to what you might gain with #3.  With  a ground shared by 4 other units being used you could open door for possible RFI in other units. Reason you use a separate ground is to keep stray RF current out of ground return path on main panel. There is nowhere near your condo you can spike in a few ground rods? They could be in lawn and fully buried. When my power company installed new ground rods on my service pole they drove in several from a common place but drove them in at angles so they "fanned" out under ground.
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KB1VCZ
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« Reply #4 on: April 14, 2011, 06:55:12 PM »

I'm not quite sure what you mean by a separate ground--do you mean an earth ground totally isolated from the AC ground or one that is bonded with the AC ground?

If you simply mean a separate ground rod, then yes, I can put one right outside next to my shack, but again, it will need to be bonded to the AC ground per the NEC.

And as I explained, the placement of the AC ground rod at the meter box makes this impossible for me to do directly, rod to rod, unless I use the existing ground wire coming from the AC ground rod at the meter to my AC service entrance.

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W8JX
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« Reply #5 on: April 14, 2011, 09:10:28 PM »

For shack you want a separate ground for RF ground not one that is bonded to AC ground. I am not sure why you feel you must bond a RF ground to AC ground here? You want to try to prevent a ground loop here not extend it.
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K9KJM
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« Reply #6 on: April 14, 2011, 10:27:17 PM »

Each thing you ground needs to go to it's own ground rod(s) FIRST.   Then those ground rods need to be all bonded together. (With power, Telco, CATV, etc)

Sounds to me like your #2 option.

#6 copper is considered the minimum gauge for the bonding.  Flat copper strap, Heavier gauge wire, Or copper tube also works well.

To install "separate" gound systems is just asking for damage from surges and lightning. 
Not just my opinion, Proven facts AND NEC code.

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W8JX
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« Reply #7 on: April 15, 2011, 06:35:44 AM »


To install "separate" gound systems is just asking for damage from surges and lightning. 
Not just my opinion, Proven facts AND NEC code.


I have had a separate grounds for 25 years here. One for power and one for RF and only lightning damage I have seen in 3 hits has came down power leg because of bad ground on service transformer on pole and other two were from EMP from very near strikes. In none of the hits were radios damaged. BTW my out builds have separate ground rods for their sub panels and they are not bonded back to main service either.
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AA4PB
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« Reply #8 on: April 15, 2011, 08:00:15 AM »

"BTW my out builds have separate ground rods for their sub panels and they are not bonded back to main service either."

Then the installation doesn't meet NEC requirements. Sub panels have isolated neutrals but NOT isolated grounds. The NEC requires grounding systems to be interconnected in all cases. This is a personel safety issue more than lightning protection.

Ever seen sparks when you connect your coax shield to the radio? I have. Ever had one arm resting on the radio when you grab that coax connector? I have and it doesn't feel good. That's why grounds should be bonded together - so that there can't be any significant voltage difference between them.
« Last Edit: April 15, 2011, 08:04:19 AM by AA4PB » Logged
KB1VCZ
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« Reply #9 on: April 15, 2011, 08:14:27 AM »

I agree that the information provided above is against NEC code and all known good practices of station grounding.

Now, back to my situation:

Well here is a picture of what I believe is the best solution for my situation.

http://i53.tinypic.com/2w6hqie.png

The orange line is the proposed bonding path, but I'm not quite sure about it, since all the diagrams I have seen simply show the direct red line bonding connection from station ground rod to AC ground rod. (Again, I can't bond directly via an underground red line path.)

So, would it be ok to simply bond at the junction box outside via the orange line since the red line bonding is out of the question?

And if I can do that, does that mean I don't need the connection from the SPG to the AC panel ground, which is labeled #1?

These are the two points that I'm unclear on.

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AA4PB
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« Reply #10 on: April 15, 2011, 08:45:53 AM »

The orange wire is fine. It would even provide a lower resistance connection than the red wire. The bond between your single point ground and the service panel should also meet the NEC requirements, provided that a minimum of #6 wire is used. If that bond is properly done, you don't even need the orange wire in my opinion.

73,
Bob
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KB1VCZ
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« Reply #11 on: April 15, 2011, 09:29:48 AM »

Do you mean that I wouldn't need the orange wire, but i could still keep the station ground rod, as long as my SPG to AC panel bond was done properly.

Or, do you mean get rid of the orange line and station ground rod and just use the SPG to AC panel ground path?

I think you mean the former, but want to be sure.

This is where I get confused with the term bonding.

You seem to be saying that as long as I'm connected properly to the AC main ground, SPG to AC panel ground in my example, that I should be ok.

I have alway thought that the bonding meant a direct connection from rod to rod.

So confusing!

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AA4PB
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« Reply #12 on: April 15, 2011, 05:25:59 PM »

Bonding just means that it is a permanent connection that is not via some connector or plug that someone can undo. It doesn't mean that the connection has to be direct from ground rod to ground rod. The NEC says that you must bond the "grounding systems". The service panel ground is part of the electrical "system" so you can bond the panel to the single point plate for your station ground. It serves the purpose very well to ensure that the electrical system ground connections and your station ground connections are at the same voltage reference inside the shack.
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K1CJS
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« Reply #13 on: April 16, 2011, 07:16:32 AM »

As Bob, AA4PB said, the grounding systems MUST be bonded together.  You can put in your own grounding rods, but they MUST be bonded to the electrical mains ground rod.  The easiest way to do that may be to put a ground clamp on the cold water pipe in the basement near your shack, and simply run a cable from your grounding system to that ground clamp.

The 'grounding' we're talking about is a SAFETY ground, not a RF ground.  (Ground rods make very poor RF grounds anyway.)  Ground rods driven in at different places--even just twenty feet apart--can have a potential voltage difference under load.  That is because of the varying resistance of the earth.  The safety aspect--bonding the grounds together--comes in so that if you touch an electrically grounded (through the electrical panel) appliance such as your power supply, and your rig--which would be grounded by your shack ground, at the same time, YOU wouldn't be the 'bond' that connects those different ground systems---and electrocute yourself in the process.
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KB1VCZ
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« Reply #14 on: April 18, 2011, 11:12:49 AM »

As Bob, AA4PB said, the grounding systems MUST be bonded together.  You can put in your own grounding rods, but they MUST be bonded to the electrical mains ground rod.  The easiest way to do that may be to put a ground clamp on the cold water pipe in the basement near your shack, and simply run a cable from your grounding system to that ground clamp.

The 'grounding' we're talking about is a SAFETY ground, not a RF ground.  (Ground rods make very poor RF grounds anyway.)  Ground rods driven in at different places--even just twenty feet apart--can have a potential voltage difference under load.  That is because of the varying resistance of the earth.  The safety aspect--bonding the grounds together--comes in so that if you touch an electrically grounded (through the electrical panel) appliance such as your power supply, and your rig--which would be grounded by your shack ground, at the same time, YOU wouldn't be the 'bond' that connects those different ground systems---and electrocute yourself in the process.

I'm with you guys on all this 100%, I understand WHY you must bond things together, but I was unclear as to the ACTUAL connections that need to take place when one considers grounding rods and AC panels since there are multiple ways to accomplish the one system SPG.

I think for now, I will simply bond my SPG bar in the shack to the AC ground panel via a 1 foot heavy copper wire or strap.

My second question though relates to how I can ground my coax runs coming into the shack, given that they enter from the opposite end of the house.

The distance to my SPG in the shack is about 30ft roughly with my antennas on the deck above the garage.

Most of what I read involves grounding the antennas at a bulkhead connector to a separate ground rod that is then tied to the other grounds and then ultimately to the “system” ground at a SPG, in keeping with what we have discussed above, but since I can’t connect via the ground rod in this instance due to distance and the fact that the “ground” in my case is asphalt, how do I then tie the antenna safety ground back into the SPG ground for the entire system?

Can I simply run a 35ft ground wire from the bulkhead plate back to the SPG in the shack?

Or, would that only be advisable if I could first drive a ground rod through the asphalt at the coax entrance and run a ground wire from the bulkhead plate to that ground rod, since that would help diffuse the energy from a strike to an antenna OUTSIDE of the house?

In that case, I would have a ground rod just outside where the coax comes in that would be connected to a bulkhead coax plate of some sort, which was in turn connected back to the SPG in the shack.

I guess the other option would be to simply not ground the coax coming in at all and just unplug the coax from the bulkhead connector when it looks like lightning may be a problem.

I hope my question here related to grounding the coax is clear!  : )

Anyway, I appreciate the comments and help.
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