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Author Topic: Temporary grounding  (Read 5281 times)

Stephen Swaffer

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Temporary grounding
« on: April 01, 2016, 10:24:47 pm »

There have been past threads discussing temporary grounding methods.  The president of the local ham club and a POCO employee told me about this-which they (I guess us since I am getting involved) use for their temporary generator setups during field days:

http://www.jharlen.com/hasfib4370.html

Not sure how the inspectors would view a 6 ft rod vs an 8 ft-but I thought I saw something arguing that the screw threads added contact area?  Certainly better than nothing.

Not cheap-but maybe cheaper than a chiropractor or doctor visit from driving a rod and pulling it.

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Tim McCulloch

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Re: Temporary grounding
« Reply #1 on: April 01, 2016, 10:40:32 pm »

There have been past threads discussing temporary grounding methods.  The president of the local ham club and a POCO employee told me about this-which they (I guess us since I am getting involved) use for their temporary generator setups during field days:

http://www.jharlen.com/hasfib4370.html

Not sure how the inspectors would view a 6 ft rod vs an 8 ft-but I thought I saw something arguing that the screw threads added contact area?  Certainly better than nothing.

Not cheap-but maybe cheaper than a chiropractor or doctor visit from driving a rod and pulling it.

The augur screw ground rod comes in a couple of different flavors, IIRC, but it's common kit on lineman's bucket trucks.

For pulling conventional ground rods I've seen a fence post puller used.

Ask yourself "what would a farmer do?"  ;)
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Lyle Williams

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Re: Temporary grounding
« Reply #2 on: April 01, 2016, 11:39:50 pm »

Ground rods are cheap.  It's easier to keep driving them than to pull them.
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Lee Buckalew

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Re: Temporary grounding
« Reply #3 on: April 02, 2016, 12:50:20 am »

Ground rods are cheap.  It's easier to keep driving them than to pull them.

When I was doing festivals we would dig a hole before driving the ground rod then drive the rod in the hole.  Didn't need to be super deep but it let us drive the rod and simply disconnect from it and backfill the hole when we were done. 

Lee
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Mike Sokol

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Re: Temporary grounding
« Reply #4 on: April 02, 2016, 08:29:12 am »

When I was doing festivals we would dig a hole before driving the ground rod then drive the rod in the hole.  Didn't need to be super deep but it let us drive the rod and simply disconnect from it and backfill the hole when we were done. 

Lee

I've just begun experiments with my bed-o-nails ground plate design. Basically, this uses a dozen or more 12" landscape spikes through a common plate. Since these spikes will penetrate the ground less than a foot, they should be well above the 18" minimum buried depth of water pipes and underground wiring in my part of the country. And they're a lot easier to pull out of the ground compared to an 8 ft ground rod. I think you could pound in a dozen or so 12" spikes and dump a gallon of water on this grounding plate for a good temporary ground. However, I need to run a fall of potential test on my prototype unit to see how well it really works before I suggest it as a possibility. And it will need to be documented to even have a chance of passing an inspection. 
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Frank DeWitt

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Re: Temporary grounding
« Reply #5 on: April 02, 2016, 01:32:17 pm »

Ask yourself "what would a farmer do?"  ;)

Always good advise but be advised, it often involves welding.
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John Roberts {JR}

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Re: Temporary grounding
« Reply #6 on: April 02, 2016, 05:05:16 pm »

I expect results may depend on how deep the local water table is. In my yard the 12" spikes would be fine and probably rust away but I can imagine geographies where 12" may still be in the relatively dry surface zone.

A bunch of short spike in parallel only works equivalent if the soil is the same conductivity near the surface and deeper. 

FWIW the spikes don't need to be large diameter (acupuncture needles), but that is likely determined by the mechanical stresses to punch through several feet of dirt. 

JR
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Mike Sokol

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Re: Temporary grounding
« Reply #7 on: April 02, 2016, 05:47:51 pm »

A bunch of short spike in parallel only works equivalent if the soil is the same conductivity near the surface and deeper. 

The plan would be to use this as a temp generator ground for a few days at most. And the dirt around it could be kept wet by dumping a gallon of water on it every day. I get a little worried when I see someone driving an 8-ft ground rod with possible underground pipes and wires.

I've got all the parts, I just need to assemble it and take some fall-of-potential measurements. An 8-ft ground rod will typically measure around 25 ohms impedance if it's in decent shape in conductive soil, and up to 100 ohms if the soil is really dry. It will be interesting to see exactly what impedance a dozen 12" spikes in wet ground will have.   

I'm going to try galvanized landscape spikes first since they're designed to be driven into the dirt, and cost less than a buck a piece. I've got a simple holder designed that will bond them all together and let you lever the spikes out of the dirt when the show is finished.

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Frank Koenig

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Re: Temporary grounding
« Reply #8 on: April 03, 2016, 12:45:27 pm »

I've just begun experiments with my bed-o-nails ground plate design.

Another thing to consider when pounding 8 or 10 ft. ground rods into every city park, corporate parking lot, or back yard where you have a gig is what it might hit under ground. Maybe you just bust the sprinkler system or maybe you puncture a gas line and take out a city block. (Gas can flow along the outside of a damaged pipe and into confined spaces.) So, I agree, once it's in leave it there for next year's event, but a shallow grounding solution sounds very attractive to avoid this risk.

Best,

--Frank
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Lyle Williams

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Re: Temporary grounding
« Reply #9 on: April 03, 2016, 04:39:56 pm »

Always good advise but be advised, it often involves welding.

I went to an accident where a fire truck had rolled off the side of a country road into a creek (it was on it's side in the water.)  When the dozer turned up I thought it was going to make a mess of the truck pulling it back up the hill.

The dozer driver proceeded to shift the level of the roadway down to the fire truck, and then flip the truck neatly back on it's wheels.

Farmers think in ways mere mortals can't.  Farmers can also do things that mortal's can't.

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Re: Temporary grounding
« Reply #9 on: April 03, 2016, 04:39:56 pm »


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