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trekkiejt 06-04-2012 01:41 AM

Grounding confusion.
Hello, I have a confusing situation. The house we just bought has the original ungrounded wiring from 1957 (I know, ick). However, there is a ground spike by the house below the meter with clamp and about 2 inches of bare copper wire attached to it where it has been cut off. It is corroded so it is not new by any means. My question is, why would there be grounding set up but unused?

I plan on using that rod by the way when I fix/update the wiring.

k_buz 06-04-2012 04:56 AM

#1 Why do you think you have ungrounded wiring in the house?

#2 You answered your own question. It was probably used at one time and now it has either been stolen, broke off, or corroded.

#3 When you upgrade the wiring, if you are talking about a service upgrade, you will be required to install 2 new ground rods (unless you can prove one new ground rod has less than 25 ohms)

Jim Port 06-04-2012 07:05 AM

Two prong receptacles and ungrounded wiring have nothing to do with a ground rod. Ground rods are for things like lightning strikes.

Grounded receptacles would require either an approved metallic wiring method or a third conductor run to the devices.

trekkiejt 06-04-2012 09:13 AM

I have all 2 prong outlets and on the panel there is only black and white wires, nothing attached to the grounding bar. I know it's original wiring because it is fabric wrapped wiring with only 2 wires to everything. There is also no hole in the house nearby the rod for wire to have been run outside. That just confuses me why it would be there and not used. I don't have a clue as to even when or for what it was used. Does the wire go to the meter and then into the house there?

trekkiejt 06-04-2012 09:19 AM

Hey Jim, when I replace the wiring what do I attach to the grounding bar in the panel for the current to go to if not the grounding rods? I've seen the ground tied into the neutral bar, is that what is supposed to be done? That is how the sub-panel fuse box in the garage is currently done.

Jim Port 06-04-2012 09:32 AM

The grounding conductor would run to the neutral bar in your service panel.

For all the trouble to run a new conductor you may be better off to just run new grounded circuits and add new receptacles.

a_lost_shadow 06-04-2012 01:20 PM

The correct way to have it connected is:

At the main panel (all bonded together):
- Incoming neutral
- All outgoing neutrals
- All outgoing grounds
- The metal enclosure
- The grounding electrode(s) (ground rods, ground plates, water pipes, etc.)

At the sub panels:
- All neutrals bonded together
- All grounds & the metal enclosure bonded together (but separate from the neutrals)

The grounding electrode has a different purpose from the grounding conductors run to the outlets. The grounding conductors provide a low resistance path from the outlets to the main panel. Thus if a device shorts the ground and a hot, the current will flow into the ground wire, back to the main service panel, and back to the utility via the service neutral. The resistance should be low enough here to allow the current to trip a breaker.

The grounding electrode on the other hand keeps your neutral at the same potential (0 V) as the ground (when no current is flowing). This means that any charge that builds up on the neutral line (static charge, nearby lightning strike, induction from the hot wires, etc.) can discharge to the ground.

Without the grounding electrode, it would be possible for your neutral line to "float" (have a voltage difference between it and the ground). Your electricity would still work, since the power company still provides the 120V difference between each phase and the incoming ground. However, in certain circumstances you could see some minor odd effects from the floating neutral, i.e. a temporary voltage drop, improper operation of equipment with its own ground, greater chance of arcing between hot and grounded objects, etc. However, most of these probably wouldn't be seen in a residential situation.

AllanJ 06-04-2012 03:23 PM

The old grounding spike (ground rod) might have been used at one time for:
1. A TV antenna,
2. A ham radio,
3. A lightning rod,
4. To ground the conduits and boxes associated with the meter and the service wires including bonding to the (single) neutral/ground/messenger wire between the house and the utility pole, the latter wire being the neutral going into your panel.

The most modern standards have the neutral between the house and the utility pole bonded to separate grounding electrodes at both ends. At the house end the grounding electrode (e.g. ground rod) is connected to a (usually) #6 copper) wire (grounding electrode conductor) that is in turn connected to the neutral bus of the panel where the first main disconnecting switch/breaker is. At the pole end the aforementioned neutral is connected to a continuous ground wire that runs from pole to pole with vertical ground wires at various poles going down to ground rods at the bottoms of those poles. The ground wire from pole to pole may also be a messenger and neutral for a pair of 120/240 volt hot wires from a pole transformer to a number of homes on the street.

trekkiejt 06-06-2012 01:21 AM

Wow, there's a lot more to this grounding thing than I thought. What do you guys recommend I do with it/where do I wire it? I plan on also using my cold water line where it is coming into the basement between the wall and the meter as another ground point. This I will do when I start replacing the 2-wire system--one outlet at a time (once I get a ladder and can get into the attic that is.) Also if I can reuse the metal receptacle boxes should I? The wire is just clamped inside the box.

AllanJ 06-06-2012 06:54 AM

Modern standards require using the cold water pipe (if metal entering the house) as another ground point (grounding electrode) using a (grounding electrode conductor consisting of a) #6 copper wire for service up to 100 amps or a #4 copper wire for service up to 200 amps, running to the panel neutral bus bar. If this GEC should first reach another GEC of at least the same size, perhaps run between a ground rod and the panel, it may end there instead of going all the way to the panel.

The connection to the pipe must be before an interior meter and within 5 feet of where the pipe enters the house. To properly ground the plumbing system, among other things, you should add a #6 copper wire jumper around the water meter and between the cold inlet and hot outlet of the water heater. Use the same kind of clamps to hold these jumper wires on.

Generally you can re-use all of the old boxes but it is possible that some may be too small for the number of wires entering them together with added ground wires, according to modern rules.

Modern ground rods must be 8 feet long, driven down essentially flush with the ground. Normally you need two.

A thorough job would include replacing all of the 2 conductor branch circuit wiring with wiring containing ground wires (equipment grounding conductors). You will need to get a permit but you can do this work at your leisure.

trekkiejt 06-06-2012 10:52 PM

The cold water is a metal pipe entering the house and about four feet inside is the meter but from there on all the supply lines are PVC. Does that make a difference or do I need to put an electrode into the pipes on each side of the water heater?

I plan to replace all the 50 yr old wiring with 12/2. I've already replaced all the switches. They had wood in them.

JeffT 06-06-2012 11:22 PM

Allan: I'm confused by this: "To properly ground the [COLOR=blue !important][COLOR=blue !important]plumbing [COLOR=blue !important]system[/COLOR][/COLOR][/COLOR], among other things, you should add a #6 copper wire jumper around the water meter and between the cold inlet and hot outlet of the water heater."

I thought that the grounding wire just had to jump over the meter, say from the cold pipe on the house side of the meter to the actual inlet from the street, on the other side of the meter; and that this was to insure electrical ground continuity in the event the meter was taken out, for whatever reason.


And why would I go to the hot outlet of the water heater?


AllanJ 06-07-2012 09:50 AM

Grounding the plumbing system is a separate project that usually does not have to be completed at the same time you upgrade your electrical system.

Some water heater connections have plastic bushings embedded in some of the parts in the hot line and the cold line going into the tank. This isolates the hot water plumbing structure until a jumper wire is put between the cold pipe and the hot pipe at the heater, or a similar longer jumper is put from some point on the hot plumbing structure to the cold plumbing structure.

Even if the pipe connections are all metal, jumpering the hot and cold connections will reduce the chance of an undetected fault (unwanted current flow or leakage) between a hot water pipe and some electrified object shortening the water heater tank life.

These jumpers are meant to ensure electrical ground continuity for the plumbing system (also requires by code in some cities), not electrical ground continuity for the electrical system. Assuming that the fat ground wire to the cold water pipe was attached to the pipe between the wall and an indoor meter, the electrical system will function properly without the meter jumper.

trekkiejt 06-07-2012 10:55 PM

So, should I jumper the hot water heater with the PVC in and out?

sirsparksalot 06-08-2012 12:57 AM


Originally Posted by trekkiejt (Post 938797)
So, should I jumper the hot water heater with the PVC in and out?

250.104 seems to imply that all water pipes be bonded, so it couldn't hurt?

250.104 Bonding of Piping Systems and Exposed Structural
(A) Metal Water Piping. The metal water piping system
shall be bonded as required in (A)(1), (A)(2), or (A)(3) of
this section. The bonding jumper(s) shall be installed in
accordance with 250.64(A), (B), and (E). The points of
attachment of the bonding jumper(s) shall be accessible.

(1) General. Metal water piping system(s) installed in or
attached to a building or structure shall be bonded to the
service equipment enclosure, the grounded conductor at the
service, the grounding electrode conductor where of sufficient
size, or to the one or more grounding electrodes used.
The bonding jumper(s) shall be sized in accordance with
Table 250.66 except as permitted in 250.104(A)(2) and

EDIT: This is per 2008 Code

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