DIY Home Improvement Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
201 Posts
Discussion Starter #1
The house was wired when only one ground was required, and it visually appears a little bit worn. It may be a galvanized steel pipe. Hard to get a reading on an ohm meter.

Without disturbing it - after all, a licensed electrician did it decades ago - how feasible would it be to install a second one, just to be on the safe side? I mean, I could call out an electrician who, last I checked, would charge about $300 to replace a ground. But isn't it just a rod, $10.28 at home depot, a clamp, $2, and a wire?

Well, admittedly, there's the skill. The current ground seems to route through the conduit that has the supply main. For it to be feasible to DIY, I'd have to run the new wire into the main panel and wire to the ground bar. Square D QO panel, and a main house ground has to be a pretty heavy cable, right?

And is it legal for the second ground to take a different route, so long as it terminates on the main bus in the panel where all the other grounds and neutrals go?
 

·
Registered
Joined
·
9,274 Posts
You don't use any ordinary ohm meter to check a ground rod. You use a ground resistance clamp meter, or a three-point fall of potential ground resistance meter.

Having someone test your existing rod costs about what you were quoted for the "additional ground rod", at least in my area it does.

Did he quote one additional ground rod or replacing the ground rod with too and proper connection to other existing electrodes? There is a big difference

Depending on your soil type, driving the ground rods may not be that easy.
 

·
Registered
Joined
·
201 Posts
Discussion Starter #4 (Edited)
May I ask what you are looking to achieve by installing another rod?
If I understand how it works correctly, the current rod is galvanized pipe and is 40 years old. I read that galvanized pipe ground rods fail long before that.

I couldn't get a multimeter reading between the metal of the top of the rod and the wire that is attached to it. (or was getting mega-ohms). From what I know, there should be a path that can handle the full amperage of the largest circuit in the house in the ground rod. A circuit with mega-ohms of resistance is not such a path.

I'm not quite sure precisely why. I'm guessing that it means that if a hot wire touches the grounded casing of an appliance, enough current will flow if the ground path is good to trip the breaker, even if the neutral is disconnected. There may be other use cases the ground rod saves you from - you tell me.

Also, since the ground is tied to neutral at the box, and that neutral is tied to the POCO transformer, presumably this means both neighboring houses and possibly the transformer itself also have grounds connected to this neutral. So probably nothing bad would happen even if a large appliance had a wire touching the casing unless this neutral were also disconnected or every neighbor on the same power company transformer also had ground failure.
 

·
Registered
Joined
·
201 Posts
Discussion Starter #5
So it's not a "going to kill me next week" kind of problem, but it seems like no matter what the problem is, adding another ground couldn't hurt, right? It's literally 3 to 6 times cheaper to install another ground than to pay an electrician to even find out if the ground is ok or not...
 

·
Registered
Joined
·
2,799 Posts
NOT an electrician....but for me just bang. In another copper ground rod next to existing and move the connection over.....depending on where you live as in some areas TWO grounds are required. Think new house, electrician pounds in the ground rod and connects it up. Ron
 

·
Licensed Electrical Cont.
Joined
·
7,829 Posts
Installing an additional/new rod would not hurt one bit. It's just you are a bit off on the function and benefit of a ground rod or other electrode.

Electrodes have nothing to do with the normal day to day functionality of an electrical service or the circuits in your house. Electrodes play NO role in clearing faults and the operation of circuit breakers. The earth is to play no role in clearing faults. This is expressly spelled out in the NEC.

Here is what the NEC says about grounding electrodes:
Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

Clearing faults and tripping circuit breakers comes from the main bonding jumper in the service panel/equipment. This bond is what makes an equipment ground different from a grounding electrode. This bond is the "low-impedance" path referred to in this quote.
Here:
Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.
 

·
Registered
Joined
·
201 Posts
Discussion Starter #8
Thank you for the reply, Speedy Pete. One thing I don't quite get - you're saying the purpose of the ground is to "stabilize" the voltage to the same potential as the earth itself and to dump energy from lightning strikes.

This means that even a pretty poor connection would tend to do this, so long as the actual ground currents are very small. Even if there's a big resistance between the earth and your electrical system, since I is small, the voltage difference between earth and the electric system remains small.

So what's the deal behind dual grounds, 8 foot long copper spikes, and #6 gauge wire to make the ground connection?

As a side note, this particular house, someone helpfully installed ground wires between the washing machine and dryer and the metal water pipes. So there's at least one more connection even if the ground stake is junk.
 

·
Licensed Electrical Cont.
Joined
·
7,829 Posts
The deal with rods is the amount of current they can flow based on soil conditions. Very dry soil will hardly conduct, so a second rod is required to meet code. Thing is, we are supposed to check for resistance of one rod, if it's not adequate then we need to add a second, regardless of resistance, and that's it! So what if the resistance is still very poor? Code does not care. lol. The reason for not needing any bigger than #6 to a rod(s) is that no matter what, a ground rod(s) can only flow so much current, so the code engineers have figured out that #6cu is the biggest wire that would ever be needed to flow the current to a ground rod.

Now, you mention water pipes. Many times the connection to a water pipe is a bond, not a ground, or grounding electrode, connection. The purpose of this is to bring the metallic piping system in the house to the same potential as the main bonding jumper in the service so that if there is a fault to a metallic pipe it will trip a breaker for that circuit and safely stop the fault until it can be cleared. Same as any other "short circuit".
 

·
Registered
Joined
·
201 Posts
Discussion Starter #10
Now, you mention water pipes. Many times the connection to a water pipe is a bond, not a ground, or grounding electrode, connection. The purpose of this is to bring the metallic piping system in the house to the same potential as the main bonding jumper in the service so that if there is a fault to a metallic pipe it will trip a breaker for that circuit and safely stop the fault until it can be cleared. Same as any other "short circuit".
I really appreciated your post. So what you're saying is that while technically, if the entire plumbing network is metal, including the part that goes outside and into the earth for 50+ feet, causing it to act like a ground, the reason for the tie is to create a path to cause a breaker trip.

If I shove the tip of a multimeter into the top of the ground rod, and the other end into the ground cable a few inches away, and get no connection, this does mean I've got no ground, right? The multimeter has a battery in it, and it's measuring the current that flows if the battery is applied across that small distance in an isolated loop.

I checked the multimeter against 2 sections of the exposed ground cable, and got 0-0.1 ohms, so the multimeter works. I think it's telling me the connection between the ground rod and the cable is too corroded to function - even if the ground rod itself still works.
 

·
Licensed electrician
Joined
·
13,387 Posts
FWIW, you could stick a hot wire onto the rod and the breaker probably will not trip.

IF you want drive a new rod wherever the old GEC will reach.
 

·
Registered
Joined
·
201 Posts
Discussion Starter #12
FWIW, you could stick a hot wire onto the rod and the breaker probably will not trip.

IF you want drive a new rod wherever the old GEC will reach.
Yes. That sounds like a good, safe idea. Soil is usually wet with a lot of soft sand, so 1 rod is probably enough. $10 from home depot for the rod, $2 for the connector, and then something to drive it with. Done.
 

·
Registered
Joined
·
714 Posts
You don't use any ordinary ohm meter to check a ground rod. You use a ground resistance clamp meter, or a three-point fall of potential ground resistance meter.

Having someone test your existing rod costs about what you were quoted for the "additional ground rod", at least in my area it does.

Did he quote one additional ground rod or replacing the ground rod with too and proper connection to other existing electrodes? There is a big difference

Depending on your soil type, driving the ground rods may not be that easy.
You are about $1,100 low for my area.
 

·
Registered
Joined
·
714 Posts
If I shove the tip of a multimeter into the top of the ground rod, and the other end into the ground cable a few inches away, and get no connection, this does mean I've got no ground, right? The multimeter has a battery in it, and it's measuring the current that flows if the.

What you are doing is what we call in technical terms WASTING TIME, you are doing nothing and the results mean nothing. Nothing+ Nothing = NOTHING


A proper test of an existing driven grounding electrode system requires a three point Earth Ground Resistance tester.
 

·
Registered
Joined
·
714 Posts
Yes. That sounds like a good, safe idea. Soil is usually wet with a lot of soft sand, so 1 rod is probably enough. $10 from home depot for the rod, $2 for the connector, and then something to drive it with. Done.
And

Sand is one of the poorer soils for to try and achieve a low resistance ground.

Buy two rods, drive them 16' apart from each other, run a #6 or larger to the rods, keep sharp bends out of the conductor, terminate in panel.
 

·
Registered
Joined
·
201 Posts
Discussion Starter #17
What you are doing is what we call in technical terms WASTING TIME, you are doing nothing and the results mean nothing. Nothing+ Nothing = NOTHING.
You misunderstand what I was trying to test. I wasn't trying to test if the ground rod conducts to the soil adequately, I was trying to test if the ground rod is even connected to the house ground wire at all. See, the ground wire had come loose a couple years ago and been screwed back on. A multimeter is capable of that test - it's just another connectivity test.
 

·
Registered
Joined
·
201 Posts
Discussion Starter #19
Here is a great video on grounding and ground rods
Thanks for the link. However, in my case, the trouble I think the wire or the clamp connecting the ground wire to the ground rod is so corroded that there is no connection. This is a completely different case.
 
1 - 19 of 19 Posts
Top