Do copper or copper-clad steel ground rods disappear with time?
After 37 years, does mine need replacing?
When I put in my first burglar alarm, 37 years ago, I put in a ground rod to ground the system, and iiuc reduce the chance of lightening damage. (Nonetheless, after about 20 years, when I was leaving for work, there were wisps of smoke coming from the keypad/control usit, and it never worked again. ;-) I have a new alarm now, grounded to the same rod, but something told me the rod was gone. The top of it is still there so maybe I dreamed it, but is it likely that the part above ground is there but most of it below ground is gone, and needs replacing?
Well, it might not be too difficult to dig down a foot or two next to the rod to inspect it that far. You can always add another rod next to the first one, and many people have several rods. The more the better.
The question was mostly theoretical. Do they sometimes rot away like an electrode, or is this just a notion I got when dreaming?
That would be hard because I put the rod right between the high and low pressure lines to the AC, so no one would kick or trip on it. (If I get the AC replaced, there may be a short bit of time when nothing and no one is there, but I can't count on my being available.)
I could do that. Only takes 5 minutes. I think I already bought a rod at a hamfest (didn't have to go shopping and thinking I got a bargain, but I don't remember how much I paid and now I see they are $8 to 12. At least I didn't pay more than that.)
There are ground rod testers but I guess hardly anyone has one. It's not a typical volt/ohm meter. Supposedly, one is supposed to put the first one in then test it to see if it has under 25 ohms resistance. One is supposed to put the 2nd one in if not. The rule of thumb is to put the 2nd one in the length of the rod from the first one. How is the connection between the ground wire and the rod? That would be something you could clean up fairly easily.
My house was built in 1965, rewired in 2000. I recently found that there was a new ground rod, but the old one is still there.
I have been unable to remove the old one. It is as if it had "rusted in place". I even tried using an old bumper jack and chain to raise it. It wouldn't budge, but the chain broke!
This does not answer the question of whether it is still a good ground. Unless you have a way to test the old one, I recommend a new one.
A galvanized ground rod should be good for 15 or more years. A copper bonded steel rod should be good for 40 or more years. Stainless steel will last 75 years or more. Depends on soil type and alkalinity/acidity or salt content
By the way, ground rods are primarily for lightning and other large surges. They really don't do any practical good for short circuit protection. The equipment grounding conductors are there for that. Let's say the ground rod at your house and the one the the utility's service both meet the 25 ohm or less standard. They're in series so the two combined would have a resistance of 50 ohms. There won't be enough current flow to trip a breaker to shutdown lethal current if there is a short to metal in your house somewhere. There's a calculator here if you want to see for yourself.
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Enter 125 volts in the voltage box and 50 ohms in the resistance box. The current flow through the two rods would be 2.5 amps, nowhere nearly enough to trip a normally sized breaker or blow a normally sized fuse.
The ground rods are partly for lightning, but mainly for protection of people. Those 2 ground rods you mention are really in parallel seperted by the resistance of the wire between them, not series.
The ground rod or ground wire for the house is for when say you place your hand on the washing machine and there is a short from the hot wire to the frame of the washer. If you touch the washer and anyting else that is grounded you will not get shocked. The skin of the body has several thousand ohms of resistance, so the largest portion of the current will go to the ground by way of the grounded conductor (usually green or bare wire). The neutral wire should be connected to the ground wire at the breaker/fuse box.
You must mean the equipment grounding conductor. What if it's gone for some silly reason or the connections are bad? Will the ground rods do any good then?
Suppose the equipment grounding conductor is in good shape. What would happen if the ground rods are gone or have bad connections?
That is a by product. If the neutral wire was correct and making the connection it should, the ground rod would have no effect. If all they did was work on the ground rod wireing, there is still a problem. A proper operating circuit will operate without any ground rod at all.
If the neutral wire is not making a very good connection from the breaker box to the transformer of the power company then any unballance in the current of the two hot wires ( US power system) will cause the voltage to vary on each side of the line. So instead of having a nominal 120 volts on each side of of a 240 volt line one side will be lower in voltage as the other side is higher in voltage depending on how much current is being used.
I was going to say something along the lines of the alarm system should be grounded to the service grounding electrode system. You're not supposed to be driving separate ground rods for various systems or components. But I suppose if it's at the opposite side of the house it might be tempting to do so, not sure it buys you anything and it could make things worse.
It's the resistance of each of the rods to earth. And if any substantial current winds up flowing, like from a loose neutral, then you can have a substantial voltage difference.
Actually that's handled by the equipment grounding conductor that ties the metal washer case to the neutral at the panel. That fault current should never make it to the ground rod.
If you touch the washer and anyting else
The ground rod keeps the equipment grounding conductor and the neutral at close to earth potential.
Correct, the neutral is supposed to be taking all of the unbalanced current back to the transformer but in wye distribution, the earth is still a current path although not the primary one. Current doesn't just take the p[ath of least resistance, it takes all paths, proportioned by the relative resistance. In wye distribution, one medium voltage connection and a neutral connection to the transformer, some circuit current will always be traveling through the earth. Doing measurements on pole transformer grounding wires I have seen readings from less than one amp to almost 3 flowing through the earth. This also imposes a voltage on your neutral, even when everything is working normally and you might easily find several volts on your ground if you have a bad grounding electrode system, compared to the slab under your house, your garage floor or the dirt outside. It is easy to get a "tingle voltage". That is probably not enough to hurt you but you might be startled enough to have a secondary injury.
I probably have the best ground on my street, 5 rods around the house, a Ufer under the garage, a Ufer under my addition, 2000 square feet of bonded concrete deck and an in ground swimming pool. The current on the transformer ground at the street in front of my house is 0.3 amps but I have almost 3 on my grounding electrode conductor. (with the main breaker off). I don't have any stray voltage around my house that I can detect and my surge protections seems to be working well. I have had 2 direct hits and never lost a thing.
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