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Author Topic: Grounding question?  (Read 1658 times)
NK7Z
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« on: October 13, 2012, 04:32:06 AM »

Hello,

I have been thinking of using 8 feet of copper 1 inch pipe as my ground
rods for a new tower install...  Is this a good idea?  Would clad rods
be better?  If so why?

73's
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Dave
For reviews and setups see: http://www.nk7z.net
K1CJS
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« Reply #1 on: October 13, 2012, 05:31:18 AM »

Clad rods would be a lot easier to drive into the ground.  In any event, how many legs does that tower have?  You should have at least one ground rod for each of the tower legs and have them all bonded together.  Depending on your soil conditions (conductivity) you may have to have more--it's not unheard of to have a trio of ground rods for each leg.  This is one area that it does NOT pay to scrimp on.  Have a local tower installer make recommendation to you.  The safety of your tower, station, house/home--and even your life may depend on the grounding arrangements you make now.
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NK7Z
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« Reply #2 on: October 13, 2012, 05:40:51 AM »

Clad rods would be a lot easier to drive into the ground.  In any event, how many legs does that tower have?  You should have at least one ground rod for each of the tower legs and have them all bonded together.  Depending on your soil conditions (conductivity) you may have to have more--it's not unheard of to have a trio of ground rods for each leg.  This is one area that it does NOT pay to scrimp on.  Have a local tower installer make recommendation to you.  The safety of your tower, station, house/home--and even your life may depend on the grounding arrangements you make now.

Thank you for the kind advice!  You have hit upon exactly why I am asking!  Smiley  I am considering the use of 8 feet of copper 1 inch pipe, placed prior to backfilling, as opposed to rods.  The cladding on the rods scares me...  10 Mils, (on the rods), is not very thick, and I would assume that deteriorates quickly?  I want to put the ground system in once, do it right, and then not have to worry about it for a long time...  The tower has three legs, and the soil here is wet most all winter.  Also, we get VERY LITTLE lightening, but we do get a lightening storm every few years...  I am considering placing either a rod or pipe at each corner of the tower base, then strapping them all together, then strapping to each leg.

73's,
Dave
« Last Edit: October 13, 2012, 06:24:59 AM by NK7Z » Logged

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Dave
For reviews and setups see: http://www.nk7z.net
K1CJS
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« Reply #3 on: October 13, 2012, 06:31:30 AM »

You do have the right idea, Dave.  However, you shouldn't set eight feet as your length limit.  With ground rods--depending on soil composition and moisture--the rule usually is the longer, the better.  You want to get down into moist, conductive soil, and if you can get down below the water table level, it's even better.

On the subject of ground rods, that cladding will last just as long as the copper in those pipes will.  If you check the ground rods on some of the electrical installations that were done, and you'll see that those rods are still in good shape and that they still maintain their grounding potential even years after they've been put in the ground.  There really isn't any advantage to using copper pipe, and depending on soil conditions (acidity, corrosiveness, etc.) that copper pipe may rot through before a ground rod would.  It's really your choice, but if it were up to me, I would opt for the ground rods.
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NK7Z
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« Reply #4 on: October 13, 2012, 06:34:37 AM »

On the subject of ground rods, that cladding will last just as long as the copper in those pipes will.  If you check the ground rods on some of the electrical installations that were done, and you'll see that those rods are still in good shape and that they still maintain their grounding potential even years after they've been put in the ground.  There really isn't any advantage to using copper pipe, and depending on soil conditions (acidity, corrosiveness, etc.) that copper pipe may rot through before a ground rod would.  It's really your choice, but if it were up to me, I would opt for the ground rods.

Again, thank you!  That is exactly the information I am looking for!  Any issues with putting in rods, and then backfilling them?  Another reason I was thinking of pipe, is that I can not locate 8 foot rods anymore...  Any suggestions?
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Dave
For reviews and setups see: http://www.nk7z.net
N4CR
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« Reply #5 on: October 13, 2012, 07:22:59 AM »

Another reason I was thinking of pipe, is that I can not locate 8 foot rods anymore...  Any suggestions?

Home Depot? Lowes? Ace Hardware?

All three should carry 10' ground rods. You have a hacksaw? (but I'd use 10' if I could get them all the way in)

Also, stay away from the zinc clamps. Get the brass ones.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
NK7Z
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« Reply #6 on: October 13, 2012, 07:39:11 AM »

Thanks to all...  I will use rods, and a lot of them!  Smiley  I will also drive them in, as opposed to back-filling, found a reference to the impedance of back-filled vs, driven rods...  The driven rods are way better! 

Again, thank you all!!!
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
W8JI
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« Reply #7 on: October 13, 2012, 08:41:39 AM »

There are some unusual common ideas about ground rods.

First, one rod per leg.  Let's suume that is correct. If I have a 50 foot tall pipe support, it only needs one rod. If I have a six legged mast the same height, it needs six rods.  Does this make sense to anyone?

Second, lightning and rod depth. Does anyone think a rod or group of rods is a better path for lightning than a bunch of cables to the house that connect to everything in the house and the utilities? I can't imagine a rod, or even two or three rods, is worth much. What really helps protect against lightning is how the cables are routed and how they enter the house. That is probably 90 percent or more of any protection issue.

While I'm not disagreeing towers should have some ground rods (I almost always use four copper pipes), ground rods really are a very small part of safety. As a matter of fact, without proper entrance bonding and with a short mast or tower near the house, a ground rod might make things worse.

I would install at least a few ground rods spread some distance over trying to get an extra few feet of depth, but more important than anything, I would do a proper building entrance that follows national codes. That's where the bulk of safety is gained.

(My ground rods mostly support a buss wire that I attach multiple buried radials to. The buried radials do the bulk of lightning and RF grounding.)

73 Tom

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NK7Z
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« Reply #8 on: October 13, 2012, 10:17:26 AM »

There are some unusual common ideas about ground rods.

First, one rod per leg.  Let's suume that is correct. If I have a 50 foot tall pipe support, it only needs one rod. If I have a six legged mast the same height, it needs six rods.  Does this make sense to anyone?

Second, lightning and rod depth. Does anyone think a rod or group of rods is a better path for lightning than a bunch of cables to the house that connect to everything in the house and the utilities? I can't imagine a rod, or even two or three rods, is worth much. What really helps protect against lightning is how the cables are routed and how they enter the house. That is probably 90 percent or more of any protection issue.

While I'm not disagreeing towers should have some ground rods (I almost always use four copper pipes), ground rods really are a very small part of safety. As a matter of fact, without proper entrance bonding and with a short mast or tower near the house, a ground rod might make things worse.

I would install at least a few ground rods spread some distance over trying to get an extra few feet of depth, but more important than anything, I would do a proper building entrance that follows national codes. That's where the bulk of safety is gained.

(My ground rods mostly support a buss wire that I attach multiple buried radials to. The buried radials do the bulk of lightning and RF grounding.)

73 Tom



Thank you for the answer, which brings up my next question...  Just how thick should the ground plate be at the entrance?  I am going to run cables underground from the tower to the house, about 70 feet...  Once they come above ground, about 10 feet from the entrance, they will all be grounded in a small dog house.  Once they enter the house, they will be grounded again, using a plate to ground...  Any thoughts?
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Dave
For reviews and setups see: http://www.nk7z.net
K9FV
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« Reply #9 on: October 13, 2012, 03:26:57 PM »

This should answer most of your questions: http://www.w8ji.com/ground_systems.htm

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W8JI
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« Reply #10 on: October 13, 2012, 05:26:12 PM »

Thank you for the answer, which brings up my next question...  Just how thick should the ground plate be at the entrance?  I am going to run cables underground from the tower to the house, about 70 feet...  Once they come above ground, about 10 feet from the entrance, they will all be grounded in a small dog house.  Once they enter the house, they will be grounded again, using a plate to ground...  Any thoughts?

That sounds good. The plate does not need to be thick. Whatever mechanically will not be too flimsy will also be thick enough electrically.

I use 18 ga hard copper. That's .040 thick sheet. 
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NK7Z
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« Reply #11 on: October 13, 2012, 06:53:07 PM »

Again, thank you!
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
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