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Author Topic: Grounding "system"  (Read 672 times)
KB1LKH
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« on: January 10, 2007, 01:20:31 PM »

Hi, Chapter 4 of my General License Manual says that the National Electric Code specifies that there be "only one grounding system  for a building. That means your RF station ground must be connected to the electrical safety gound".  What confuses me is the word "system"... I assume I need to run the station ground to wherever the house ground is.  However, those diagrams I see where you have a low impedance conductor as short as possible running to an 8 foot ground rod makes me think I can install a ground to a separate location.  What is meant by the word "system"?  By the way, it appears that my house ground (here in New England) runs to the black plastic main water line that disappears into the ground ?!

Thanks,
Mike
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KB4EMF
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« Reply #1 on: January 10, 2007, 01:27:30 PM »

Don't confuse the RF ground from the safety ground.  Your RF ground needs to be as short as possible.  It basically means that the grounding rod needs to be right outside of your window.

Safety ground does not need to be shortest possible.

If you are grounding your RIG, this would be the safety ground.  Assuming you don't have "rf on coax" problem or use a tuner into a random wire.

Either way, ALL of your ground must be tied by a thick enough wire.  (I don't recall the actual requirement)

They call it "system" because with different kind of ground with different requirement, you just don't have one grounding rod and a wire.  You'll have multiple, and you  have to think of this as interconnected "system."
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N3OX
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« Reply #2 on: January 10, 2007, 02:24:54 PM »

"What is meant by the word "system"?"

Commercial installations and hams who "do it right" and install the kind of grounding where there's a tiny chance of damage from lightning strikes can give you an idea of what is meant by a "system".

A tower might have several tens of ground radials extending out a large distance in each direction, maybe wide flat copper strap or very large copper wire.  At frequent intervals along the radials, ground rods are driven and attached. This spreads out the strike energy.

The entrance panel to the building might have several ground rods (maybe even more radials) attached to it.  

What your general manual means by "one system" is that ALL of the grounding conductors and rods in and around your house and towers MUST be **bonded together** with low impedance conductors.  

If your house ground goes to a black plastic pipe, please get it fixed IMMEDIATELY.  When you set up a ham station ground, make sure your ground rods for your ham stuff are bonded together and to your newly repaired electrical ground with minimum of #4 solid wire... bigger is better, more ground rods are better.

Read up on www.polyphaser.com about good station grounding practices... I'm sure KB9CRY will drop in here sooner or later and augment that advice.

73,
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
N3OX
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« Reply #3 on: January 10, 2007, 02:27:38 PM »

Some good reading on the subject:

http://www.polyphaser.com/NR/rdonlyres/C1565001-F81A-4AC2-A98F-E88B8037F988/182/TD1016.pdf
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KB9CRY
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« Reply #4 on: January 10, 2007, 03:27:21 PM »

REad my description of the same question a couple of threads later in this forum.

Phil  KB9CRY
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KB9CRY
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« Reply #5 on: January 10, 2007, 04:42:18 PM »

Here's my post to another similar question:

The term Single Point Ground is misleading and should better be stated as Main Grounding System. It's OK to run your cables (coaxes, control lines, etc) indoors but your shack ground should go right outside to a ground rod. What you want to set up is a proper "perimeter" ground system consisting of this lone shack ground rod, then interconnected with low resistance/low impedance grounding wire or wide copper strip (I use #4 bare solid) which is routed around the house (avoid sharp bends and one could drive add'l rods along the way) and connect that to your other SPG. You don't need a complete loop around the house but this entire system (Cadweld connections would be best) can be thought of as your SPG.

Make sense now?

Phil KB9CRY

Please go to the Forums Search feature and do a search on Grounding as we've discussed this here ad nauseum.  But to summarize, I like to break a properly designed grounding system into 5 parts, each of which MUST be designed and installed to it's completeness (and it doesn't need to cost tons of money also) for it all to work or else Mother Nature will bite you.

1.  Tower/Antenna Ground
2.  Cable Arrestors
3.  SPG or Main Grounding System
4.  Shack Ground
5.  Electrical Service Entrance Ground (incl other house utilities' grounds)
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N0RZT
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« Reply #6 on: January 10, 2007, 06:44:11 PM »

Good evening,

When I read your comment about grounding to the water pipe, I was going to suggest there may not be much to worry about... in my house, either the builder or the previous owner made a low-impedance connection between the cold water pipe and the ground rod with a solid copper wire (at first I thought #6, but on second look, it could be #4) -- okay, I do have a minor assumption here: there's a wire running from the cold water pipe to the circuit breaker box, and there's a similar wire running from the circuit breaker box to the ground rod.

Then I read it again, and noticed you described it as a black pipe -- the cold water pipe in my house is bare copper; the gas pipe is painted black.

Then I read it a third time, and noticed you described it as black plastic.  That plastic pipe isn't grounding anything!
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K9KJM
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« Reply #7 on: January 10, 2007, 11:57:57 PM »

The ground "system" is all of the grounds at your house.  All need to be bonded together.
As mentioned, You might want an RF ground, A lightning protection ground, And a safety ground.
In any modern house, The outlets that have the 3rd prong grounded is usually a good safety ground.
A good lightning ground is a huge subject. For good info read;  http://members.cox.net/pc-usa/station/ground0.htm
Ground rods are usually spaced about twice the distance apart as the depth. (8 foot deep rods should be about 16 or so feet apart)
For most balanced HF antennas, No RF ground system is usually needed...........   If you do want an RF ground, A series of counterpoise wires (Radials) buried just below the surface will work, As will some elevated radial wires..........  
If buried, Use bare copper wire. If elevated, Insulated wire is best.  
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K8MHZ
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« Reply #8 on: January 11, 2007, 06:55:22 AM »

The conductors connecting the water pipes and the ground rods to the AC mains panel are for AC safety only and do not provide RF grounding nor lightning protection.

RF and lightning have different requirments and will need to be built accordingly.  Once done, they must be bonded to the AC mains system.  ALL grounding systems in a building must be bonded together.  The size of the conductor varies but a rule of thumb is to get the largest you can afford.  If you know where to get #2 Solid Bare Tinned Copper that is good stuff.

Also be aware that the bonding of one system's grounding rods to another must not pass through the building.
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KB1LKH
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« Reply #9 on: January 11, 2007, 10:15:11 AM »

Thanks to all of you for the help; though this is a well-worn topic, and I have read several other forums with related info, you took the time to help me.  Also, I appreciate you pointing out the difference between RF and system ground as well, I did kind of confuse them!

73 Mike
KB1LKH
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