Grounding Rod

[John Hines]

#6 will work.

[Bill Davis Jr]

Recently moving into an old house one of my main concerns was the electrical system.

One question I have is there a required size of cable for a 100 amp service?

When we first moved in I was looking at the service panel. I did not see a grounding cable to the outside. Which I know meant no grounding rod. What scared me the most is the grounding wire that was run went to the gas line. That for now was changed to the water line.

I would like to install the grounding rod myself but would like to know if it matters as to what size grounding cable to run for a 100 amp service.

Thanks,

Bill

[RBM]

[PrecisionMachinisT]

I would have to assume you are just plain ignorant when it comes to electricity then.......

Yes, readily apparent that's what he had meant....

Curious...got any clues as to how a megger might work ???

( this oughta be good )

In my area, with any new service two ground rods are required, and so far as I know there are no exceptions allowed whatsoever.

[Pop]

"RBM" wrote in message news:DaVDe.320$ [e-mail]...

I assume you mean a rod for each phase? Why? And what good would a "ground meger" be? I assume again the you meant "megger"?

Just curious; I have NEVER seen more than one rod used for any entrance on any house.

Pop

[RBM]

[EXT]

The gas line should be grounded, but not serve as the ground. Most gas companies will insulate the inside metal gas pipe at the meter connection from the underground metal gas pipe to reduce electrolytic caused corrosion.

[RBM]

The ground rods are required in addition to a metallic water pipe

[Ed H]

My 100 amp service required 2 ground rods, 8' apart on a continuous #6 conductor. But only because I do not have a metal water main going out that could also be grounded, mine is pvc.

Ed

[Fred]

If the house is old it probably has copper water line coming into it. This is a better ground than ground rods so one isn't required. Also, put the ground wire back on the gas line...it should be bonded to ground.

Fred

[Oscar_Lives]

Hey Poop, lighten up!

[George E. Cawthon]

Why? I have a 200 amp service and a single rod. The critical factor, at least here, is the length of the rod and depth the rod is driven down.

And, what the hell is a ground meger? Did he mean a ground meter? If so, what is a ground meter? Did he mean measure the ground with an Ohm meter?

And the response is equally crazy. "A rod on each phase" means the questioner doesn't know anything about electricity or the correct terms. And he things meger might be megger, but what the heck is megger?

[RBM]

Let me splain it: NEC rules change constantly. There was a time when, if you had a metal water pipe, it was sufficient for grounding. Next it was required to back the water pipe up with a ground rod. If you had a well with pvc you needed two ground rods. The latest change is that you must determine how well connected to the earth your ground rod is, which is done using an expensive measuring device called a megger. If you don't have one many jurisdictions require you to add an additional rod. IMHO it makes sense. If you drove an eight foot ground rod into dry sand it probably isn't going to have any connection electrically with earth

[Milos]

FDR, did your mother have any normal children?

[TURTLE]

This is Turtle.

i have a rule to go by on what size wire to use on ground rods replacements.

I get the grounding clam that will attach the wire to the clamp then to the rod. i look at the hole of the clamp where the wire attaches to the clamp and get a wire that will fill the hole completely. That is the size i use and sometimes called Big Wire. It will not hurt a think over sizing this wire.

TURTLE

[FDR]

So having two buried in sand makes sense?

[w_tom]

RBM is providing straight answers. This will expand on what he had posted.

Post 1990 codes says at least one ground rod (or equivalent and dedicated device such as earthing plate, Ufer ground, etc) close to breaker box must be installed. This earth ground (called a GEC in the code book), to earth AC electric, serves multiple electrical purposes. Its human safety purpose is defined by the National Electrical Code (NEC).

Two rods may be installed because, well, the NEC does not even properly define what is sufficient conductive earth. They provide a number (25 ohms) and don't even state how that conductivity should be measured. So many electricians just install two rods that also meet other NEC criteria such as separation between rods. Even if two rods don't make soil conductive enough, the code says an electrician need not do anything more.

The water pipe was once considered a sufficient earth ground. For numerous reasons, a water pipe is no longer sufficient as an earth ground. But water pipe must be bonded to breaker box to remove any electricity from those pipes. Electricity could be from inside the building OR electricity that could be coming from utility water pipes. The pipe must be 'bonded' to the breaker box to remove electricity. This water pipe bonding may also end up supplementing the earth ground. But code no longer views water pipe as sufficient earth ground (except in some rare cases that are irrelevant here).

Some jurisdictions require that a gas pipe also be bonded (not to be confused with earthing). That bonding requirement would be uniquely defined by the local gas company. In one example, the home had no earth ground. When a utility's street transformer failed internally, electricity used the gas pipe as an electrical conductor (because water pipe ground was compromised and dedicated earth ground was never installed). Fortunately no one was home when gas meter gaskets finally failed and the house exploded. Just one rare example of why proper earthing and proper bonding are important.

Absolute m> Recently moving into an old house one of my main concerns was the > electrical system.

[Bud]

A megger is actually used to measure very high (insulation) resistance.

To check for the required 25 ohms ground resistance you could connect the ground rod to a hot through a lightbulb and measure the current to the ground rod and the voltage from the ground rod to a metal burried water pipe.

Ground rods are not noted for being a good ground which is why #6 Cu is the wire size used to connect them. Burried metal water pipe is good. Ground rods are a hedge for conversion of metal water service pipe to plastic.

Bud--

[FDR]

Well, looks like your mother didn't rear any smart children.

[~^Johnny^~]