Two physical grounds??


Due to construction issues the only way to ground my line conditioner is by instaling a dedicated ground rod for it (i.e. the house outlets are of type that accept a 2 prong plug). This dedicated ground rod for the line conditioner will be about 16 feet away from the ground rod for the electrical wiring for my house. By doing this would I get into trouble regarding a "ground loop".
tiofelon
The problem is only if some voltage difference between the two grounds.
With the rods so close, i doubt you will have a voltage differential.
If possible it would be best to tie the 2 ground rods together. Elizabeth is right about the possible difference in ground potentials. Otherwise in a worst case scenario IF you had a direct hit by lighting the voltage would jump from 1 ground to another. This happened to an old customer in Texas and the concrete floor between the 2 ground rods exploded. Again they took a direct lightning hit.
Try running a #14 awg to the outlet that your power conditioner is using, to a cold water pipe and clamp off to that. Swap out the old two wire outlet to a new three wire grounded outlet. The NEC allows for this and will provide an equipment grounding conductor for your conditioner. You can also run an addition wire to a driven ground rod if you would like. Don’t have any idea where the neutral (grounded conduction) receives it’s ground reference and might result in noisy ground loop, if so you can buy various products to combat that and the conditioner is much safer with the grounded outlet. Good luck. T. J.
Tio, on the one hand you mention that "the house outlets are of [a] type that accept a 2 prong plug." On the other hand, when raising the possiblilty of installing a separate dedicated grounding rod for the line conditioner, you mention the new rod would be "about 16 feet away from the ground rod for the electrical wiring for my house."

I assume that the outlet in question is wired with two wire ungrounded romex. Ergo, why there's only a two plug outlet available for the line conditioner.

I hope I'm not being simple here, but if there is a grounding rod for the house, to what extent is the house wired with three wire grounded romex. That is, the various line circuits all converge to one place, the fuse or circuit box, which in turn, I assume is tied into the house ground, as required by most electric codes. If most of the house wiring is grounded romex, then you could run a new grounded romex line from the outlet that is dedicated to the line conditioner to the grounded socket.

However, if the house is old (like mine), most of the house wiring may only be old fashioned ungrounded two wire romex. If so, I like Tjt's idea the best. Maybe that would work if you can fish the ground through the wall and attach it to the water pipe.
Aren't multiple grounds as described....Against Code?

Also, Where do you find 2 prong (ungrounded) sockets?
Magfan, maybe they're really old?? Otherwise, I think most folks just slap a three prong into the outlet, but don't ground it.

As I mentioned in my post, my house is old, maybe built 50-55 years ago and was wired with 2 wire ungrounded romex. When we moved in about 18 years ago, we did a lot of home improvement and electrical work in the basement. While the basement ceiling was opened up, the electrician was able to rewire most of the 1st floor outlets with grounded romex. BTW, the electrician was licensed and his work was inspected by a township inspector to ensure all work was done in accordance with code.

FWIW
Back in the late 70s I lived in a house with 4 or 5 outlets TOTAL and push button/rocker switches for lights.
The service was Knob and Tube.....which was so old the code for it was written in Hieroglyphs. My dad, generally mello, freaked out when he saw it and 'bout demanded I move out........The house? One of the oldest in downtown Fullerton California and the very definition of 'fire trap'.

http://en.wikipedia.org/wiki/Knob_and_tube_wiring

I'm surprised. Your Romex may have been put in during a transition period between hard conduit and the newest 3-wire code. At least you didn't have Aluminum wire and fittings.
The house my dad built about '58 was all conduit which I think was the '3rd wire'.

Any of the 2-wire stuff left should be immediately upgraded to latest code. Some of the wiring...J-boxes, outlets and switches may be untouched for decades and ready-2-go.

I'm still a little......leery.....of multiple ground rods.....
Magfan, maybe it's is a local thing, but every licensed electrician who has been in the house for one reason or another says that as long as we don't mess with the old romex and don't overload the outlets, the old stuff is stable.

To undertake what I think you are suggesting, which is to change out the old 2 wire romex, would entail ripping the house apart. Most of the old wire is attached to the studwork. As I mentioned above, when the occassion arises, we always try to change over circuits to comply with modern code.

But what about the OP?? I wonder what his situation is. Btw, I'm not an electrician, so take this with a grain of salt, but I don't like the idea of two ground rods either.
If there are no other grounds, tying the two earths together is appropriate and does not create a loop if I understand what the OP is describing. The tie wire should be the same type of ground strap used from the service panel.
I'm not an electrician either. But you might be able to get a new ungrounded outlet somewhere. Another option would be to use a ground fault circuit interrupter, and I believe it needs to be labeled ungrounded on it. The extra ground rod is not an option, unless you bond them all at the service ground, per NEC, and local codes. Again I'm not an electrician. I am going by memory FWIW. That's not saying much with these middle age "senior moments". Gotta blame something.
Also make sure the hot (phase) wire and neutral are correct. There are some older products out there that have one wire tied to the case/chassis. If it's backwards, that can be a deadly mistake.
Thank you all for your responses! As some of you guessed right the house is very old with just 2 prong sockets (ungrounded). However, I know that there is a ground bar at the fuse box which would be very difficult to fish in order to tie the two ground bars togheter. Tjtrout20 suggestion seems to be the way to go. Thanks again!
The solution is easy provided you have a metal outlet box. Simply buy a 3-pronged outlet and a package of green ground wires (pre-looped, and with green screws, called 'Equipment Bonding Jumpers'). Remove one of the old two-prongers where you want to install the PC. Install the new grounded outlet to the white/black wires and install the green ground wire to the ground screw of the outlet. At the other end of the green ground wire, screw it to the metal box with the green ground screw. Push the wires back in the box and attach the outlet to the box. You now have a grounded outlet.
Gs5556,

Metal boxes were used with old 2 wire NM sheathed cable. The metallic box is floating..... Even in the case of old BX the conductivity continuity of the armor/connectors would be poor at best.
Jim
With all due respect Gs556 should not be giving electrical advice.

"The solution is easy provided you have a metal outlet box. Simply buy a 3-pronged outlet and a package of green ground wires (pre-looped, and with green screws, called 'Equipment Bonding Jumpers'). Remove one of the old two-prongers where you want to install the PC. Install the new grounded outlet to the white/black wires and install the green ground wire to the ground screw of the outlet. At the other end of the green ground wire, screw it to the metal box with the green ground screw. Push the wires back in the box and attach the outlet to the box. You now have a grounded outlet."

No… you now have an ungrounded circuit terminating to a grounded outlet. The exact same as a two wire ungrounded outlets but now not compliant with the National Electrical Code or most International Codes.
T. J.
Try running a #14 awg to the outlet that your power conditioner is using, to a cold water pipe and clamp off to that.
07-07-11: Tjtrout20
Tjtrout20,

No longer an NEC approved method. Not since 1996 I believe. Too many plumbers were getting shocked or electrocuted.
>>>>>>>>>>>>>>>

This dedicated ground rod for the line conditioner will be about 16 feet away from the ground rod for the electrical wiring for my house.
07-07-11: Tiofelon

Tiofelon,

The dedicated ground rod is a bad idea as others have pointed out. Will not meet NEC code either.....

What NEC will allow for old 2 wire ungrounded receptacle/ branch circuit is to install a new equipment ground wire and connect it to the existing main electrical grounding system, (Grounding Electrode System), of the house.

Look at running a ground wire along the exterior of the house and connect it to the ground wire that comes from the house to the existing ground rod. Use an approved wire connector such as a split bolt. DO NOT cut the main ground wire that runs to the existing ground rod......

You might also be able to run the new ground wire back into the house and connect it to the ground bar you spoke of in a later post.

Wire must be protected from physical damage. Support often.
If it were me I would use a solid #10 awg copper wire.

It would really be best to hire a licensed electrician to do the job......

Method for grounding a non grounded receptacle/branch circuit.
NEC 2008 250.130 (C)

Local code (AHJ) has the final say.
Tjtrout20,

In Gs5556 defense he may live in an area were all branch circuits must be installed in conduit. I believe Chicago as well as New York City being two that come to mind. He may have just had a brain fart and forgot not everywhere in the US require branch circuits must be installed in metallic conduit.
Jim
Jea48,
Check this from the 2011 NEC. 250.130(c)1
250.130 (C)
(C) Non grounding Receptacle Replacement or Branch
Circuit Extensions. The equipment grounding conductor
of a grounding-type receptacle or a branch-circuit extension
shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system
as described in 250.50
(2) Any accessible point on the grounding electrode conductor
(3) The equipment grounding terminal bar within the enclosure
where the branch circuit for the receptacle or
branch circuit originates
(4) For grounded systems, the grounded service conductor
within the service equipment enclosure
(5) For ungrounded systems, the grounding terminal bar
within the service equipment enclosure
The cold water pipe is part of the Grounding Electrode System. The key word is System, which includes the cold water pipe. Check 250.50 for description of GES.
This is discussed in length on Mike Holts web site.
As far as the correct size of the equipment grounding conductor for 15amp circuits #14awg copper or 20amp circuits #12awg as per 250.122 2011 NEC but nothing wrong with #10 also.
Did not mean to slam GS5556 but a blanket statement like that can get people hurt. Peace T. J.
I think the take-away here is that for hi-current electrical issues and advice, hire a PRO. someone familiar with NEC and any local issues.
Tjtrout20,

The cold water pipe is part of the Grounding Electrode System. The key word is System, which includes the cold water pipe. Check 250.50 for description of GES.
You need to go back to the book.... Only the first 5 feet from point of entrance. NEC 2008 250.52 (A) (1). "Exception" does not apply here.

I have been a little lazy and have not picked up a copy of the New 2011 NEC code......

As far as the correct size of the equipment grounding conductor for 15amp circuits #14awg copper or 20amp circuits #12awg as per 250.122 2011 NEC but nothing wrong with #10 also.
True.... I am concerned with protection from physical damage.... #10 will withstand more physical abuse than #14 or even #12. This safety equipment grounding conductor is going to be installed on the exterior of the house. More than likely by the home owner....

Code is bare minimum safety standards as you know.
Jim
Agree with Magfan. Good advice. Hire a Pro in your area :^).
Jim,
I just checked the 2008 hand book:
This 5-ft limit also applies to the replacement of nongrounding receptacles with grounding-type or branch-circuit extensions in accordance with 250.130(C). See the commentary following 250.130(C) and the illustration that accompanies that commentary, Exhibit 250.51.
I stand corrected. Not the first time! Peace T. J.
Sorry, my mistake and no offense taken. I assumed you had grounded outlet boxes. Most 2-prong receptacle wiring in older houses that I have seen built since 1960 is armored steel BX (with ground) and the outlet ears against plaster so installing a grounded outlet was... easy. I had gone with I was familiar with; I should have clarified with a question first.