Thursday, July 10, 2014

What you need to know about ground rods

Make sure ground wires are firmly connected to the ground rod. 
Ground rods may seem to be just a trivial item. After all, they're just a metal rod you pound into the ground. They seem more of an anchor for the energizer than anything else. Don't be deceived by their unassuming demeanor, ground rods are vital.

How so? Try using an electric fence without the recommended amount of ground rod (3 ft per joule of output). For example, if using a PRS 100, an energizer with 1 joule of output, pull the ground rod out of the ground by a foot or two. Check the voltage of your fence (with a fence tester). Pound the rod back into the ground. Check the voltage again. See a difference?

We've established that it's important. Next, let's look into how an electric fence works. 
  1. The energizer fence terminal sends an electric pulse through the fence's conductor(s). 
  2. An animal touches the conductor
  3. The pulse travels from the fence through the animal and into the ground. 
  4. The pulse moves through the soil (via moisture) and to the ground rod. 
  5. The pulse goes up through the ground rod and back to the energizer (via the ground rod). Completing the circuit (and the animal receives a shock, learning to stay away from the fence). 
Note: all of above happens in 1/10,000 of a second. 

So what does the ground rod do? It picks up the pulse from the ground and brings it back to the energizer. 

However, if the energizer has a stronger pulse than the rod can pick up, an electrical charge can build up around the rod. Since the full power of the pulse cannot travel through the ground rod, an animal will not receive a full powered shock. The remedy? Pour water around the ground rod to increase the conductivity around the ground rod(s), or add additional rods. 

Why is this ground rod so far out of the ground? It's likely because we are using a 1 joule energizer and a 6' ft ground. At 3' of rod needed per joule output, the full 6' is unnecessary. 
It is possible to test to see if your ground rod is not adequate. Ground out the fence—with the fence off, place a metal rod on the ground and lean it against the fence's conductors. This will cause a 'dead-short' to the ground. Using a digital voltmeter, stick the ground probe into the ground and touch the fence probe to the rod. If a reading of more than 300v appears, you need more ground rod. Under 300v, you have adequate grounding.

Connecting an energizer to its grounding system.