I have a piece of rebar, 36" long, 1"dia. that I want to use as a grounding rod for an electrical fence.
This rod has a lot of rust on it so my questions are, should I wire brush, or sand this rust off, so as to maximize conductivity?
How deeply should I bury the rod?
TIA.
Lewis.
*****
Er, no. It's just going to rust again and your work will be for naught.
A. You don't "bury" the rod, you drive it into the ground.
B. Depth depends on soil conditions. What do the instructions for your electric fence say?
It might be OK for an electric farm animal fence. But I agree with your points above. He can clean that rebar all he wants, but all you have to do is look at it and it will rust again. They rust just sitting in a garage. Exposed, outside, it's going to rust again, including the contact area between the wire and bar.
Rebar is the wrong material to use for a grounding rod. There is a reason why copper rods are used for this application. You don't want a rod that rusts away over time. Home Depot and Lowes sell the correct copper rods, and they are not terribly expensive. Use one instead of rebar.
I'm not familiar with the specifics of electric fences, but the requirements for grounding a house require much longer rods. And with house construction people commonly use two rods spaced a distance apart to improve conductivity.
No need.
Leave only enough exposed as necessary to get the cable bonding clamp on the end of it - an inch or two. And when you say bury, you really mean how far should you pound it into the ground, right?
R
the ground rods sold at home depot etc arent copper they are copper plated steel......
if the OP can put the electric fence charger near the homes service entrance they could connect a copper cable to it for grounding purposes. or buy a copper plated ground rod, they rust very slowly....
using the rusty rebar isnt worth the effort
I would not worry about the rust as in a month there will be more rust on it.
YOu should look here about ground rods for the fence.
There is a reason why most ground spikes are made of copper Rust is not know as a good conductor
Yes, you're right. I thought per NEC they now had to be copper, but galvanized pipe is still OK.
Does the NEC code quoted above pertain to electric fencing? The beginning part of that NEC section reads:
E3508 GROUNDING ELECTRODE SYSTEM
=A7E3508.1 Grounding electrode system. Where available on the premises at each building or structure served, electrodes specified in =A7E3508.1.1, =A7E3508.1.2 and =A7E3508.1.3, and any made electrodes specified in =A7E3508.2, shall be bonded together to form the grounding electrode system.
A fence is not a building or structure. I have an older copy of the code so maybe the wording has changed, but I don't know that that section of the NEC applies.
R
...
'Pends on where you're located--if it's only 3-ft, drive most of it, anyway. If it's enough, you'll know it when you grab 'hold the fence to test it... :)
The minimum you can get by with (but why worry about it, anyway; it's a trivial exercise) will depend on how damp a climate you're in so how much the top of the ground and how deeply the ground dries out to the point of not having good enough conductivity. Here it needs to be pretty deep for mid-summer when things get very dry, but 3-ft will generally work even then.
Secondarily, how much ground you need depends on the length of wire, the power of the charger and what you're trying to keep in as well as the ground conditions. If it's very dry the critters don't has as good a ground, either...when it's damp they'll get a much better jolt.
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I was discussing it only in the context of a ground round for residential use in general, not specific to the animal fence application. The reference from Bob is from the International Code Council, but it's consistent with NEC.
If a galvanized pipe is good enough for the NEC for a residential ground, then it's good enough for me for the animal fence. Strictly speaking and to your point, I don;t know what specifically would apply to the application. One would think the installation instructions would hopefully be in compliance.
It would not not be power or wire length, it's high voltage low current. It's not how deep, but how good a ground. The critter is only on surface level the current must travel through the ground to get any shock. Nec guidelines apply to high current safety.
You don't pound ground ground rods unless you hit thin rock, and can get stuck, and have to cut off and work another if it was not deep enough.
Greg
to test it... :)
So, the same charger that puts out say 3000 volts at 5 milliamps on 5 miles of wire will have the same effect as a charger that puts out 3000 volts at 20 milliamps on 200 ft of wire?
If you don't pound ground rods unless they hit a rock, then how are you supposed to get them in? Talk to them?
I guess most of the responders have never set up an electric fence.
The only problem you may have is getting a good metallic connection between the rebar and your ground wire. You can do this by grinding the rust off a bit of the rebar and using a ground wire clamp from your local hardware store. Smear with grease before clamping the wire.
If you soil is damp, you don't need to drive the rebar in very far. If dry soil, then drive it as far as possible. The 5,000 to 10,000 volt pulse will pass right through the damp rust, or even the dry rust.
Get an electric fence tester and check for voltage at several places along the fence. My tester is a plastic box with several neon bulbs that flash for different electric fence voltages. A wire has a stainless steel wand about 3 inches long to press into the soil, then touch the fence wire with a probe on the tester. Other testers may be different.
If you can't drive the rod due to rocks, burying it is also fine.
I live in the Central Oregon desert and the previous owner fastened wire to rebar and buried it for the fence ground. I moved to a different location and was able drive a rod for 2-3 feet.
Good luck. Paul
An electrician showed me, at least near Pittsburgh. You pour water down working the pole up and down with your hand !!! As the pole goes deeper, add more water. It goes right down. I've done 6 foot rods. One got stuck couple feet from top. Used sledge to get in a little deeper.
I'm sure I'll get at least one comment on this one !
Greg
I knew an older fella that installed radio and tv antennas and maybe even c-band satellites that all needed grounding rods.
He told me once about 15 years ago he always used water to soften the ground then push the grounding rod (usually galvanized piping) into the soft spot. I thought it strange then.
for electric fence, as long as you get a good connection attaching the conductor to the rebar, just drive it in the ground. It'll be good.
test it... :)
ya, that might work on the beach. Not in dirt or clay.
I farm and have electric fences. Rebar is not very good, and 3 ft. is too short. The copper clad rods made for electric grounds is the best, but 1/2 or 3/4" galvanized pipe will work in a pinch. But go at least 5 feet long. Leave 3 or 4" sticking out of the ground for the clamp, pound in the rest of it. 6 feet is better, 8 is approved for code of electrical systems, but there is no code for electric fences.
Here's a hard learned tip. Soem years ago I had a piece of 1/2" EMT conduit about 30" long and pounded that in. It was only meant to be temporary. But it remained for a few years. Well, we got a dry spell, the soil cracked, and soon I had loose horses. They were not getting jolted, yet the fence was turned on and not shorted. I tested the fence and re-tested it, and re-checked it, and everything was good. The controller showed a good
5kv on my tester across the terminals. I finally thought I better check the ground to be sure the wire was well clamped to the pipe. I touched that ground rod and was knocked right on my ass. The jolt was 5 times stronger than just touching the fence when live. It turned out that the soil was so dry that the ground was not working any more.I wet the soil around the ground rod and the fence worked again. That's when I bought a 6ft, copper clad ground rod and never had a problem since. EMT couduit was poor to begin, then the soil was dry probably all the way to the bottom of that pipe. At 6 feet down, the soil is not likely to dry out completely.
Note, in sandy areas, you may need more than one rod, spaced at least
10ft. apart and wired together with #8 or #6 solid copper wire.One last note. In a drought, the soil is so dry that the animals hooves are not making a good ground. We are currently having this problem. I touched the fence myself and barely got a tingle, and I was only wearing tennis shoes. I did some hosing of the ground near the places the animals like to lean over the fence to get some of that "greener grass".
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