Sharing ground wire between two dedicated circuits

@emergingsoul said:

Idea has been proposed to share the insulated ground from the 10/3 wire with the other 10/2 dedicated circuit. Achieves the same thing at a lot less cost? Does this make sense?

No not to me it doesn’t. Per NEC the EGC, "(Equipment Grounding Conductor), shall be installed in the same raceway, or cable, as the branch circuit conductors.

You are planing on using the EGC of the 10/3 NM cable, (Romex is a trade name), for the EGC in the 10/2 NM cable.

Just curious what’s your reasoning or importance for the EGC being insulated in a PVC jacketed cable. The EGC has one purpose. To carry ground fault current back to the source.

You didn’t say what type of outlets you are going to use. IF you are planing on using IG, (Isolated Ground), outlets they would not serve any purpose whats so ever connected to MN cable. None...

I assume you will be hiring an electrician to do the wiring project. A reputable Licensed Electrician will not do what you want to do with the green taped insulated EGC from the 10/3 NM cable.

Just use 10/2 NM for both branch circuits or better use 10/2 solid aluminum armored MC cable. The EGC is insulated green in color. The three conductors are tightly twisted spiral its entire length. Very tightly twisted...

Example Aluminum Armored 10/2 MC cable. (Tell the Electrician yo want solid core conductors only...)

Southwire Armorlite 250-ft 10 / 2 Solid Aluminum Mc Cable

You can also use plastic boxes for the outlets instead of steel boxes if you want. It meets NEC code. With that said the AHJ, (Authority Having Jurisdiction), has the final say. Your electrician will know...

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Integrating Electronic Equipment and Power into Rack ...

Go to page 12 and page 13

Two conductor plus 1 ground MC (Metal Clad) is a good choice for Non-Isolated Ground A/V systems. MC cable contains a safety
grounding conductor (wire). The three conductors in the MC cable (Line, Neutral and Ground) are uniformly twisted, reducing both
induced voltages on the ground wire and radiated AC magnetic fields. The NEC article 250.118 (10)a prohibits the use of this cable for
isolated ground circuits because the metal jacket is not considered a grounding conductor, and it is not rated for fault current.

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emergingsoul OP

468 posts

12-08-2022 at 02:39pm

So it sounds like having an insulated ground back to the panel doesn’t matter. What about interference, all that noise and crap being diverted back to the panel via ground. Why would I want noise from in uninsulated ground to be used???

@emergingsoul

The EGC, (Equipment Grounding Conductor), is for safety. In the event of a HOT to chassis fault it carries the ground fault current back to the source. Not all equipment uses an EGC conductor. How about a piece of digital equipment that has a cheap SMPS that is fed by 2 wire only, (Hot and Neutral conductors), that does not use an EGC. "All that noise and crap" travels back out on the AC mains. Even if the equipment uses an EGC "All that noise and crap" still travels back out on the AC mains.

What about interference, all that noise and crap being diverted back to the panel via ground.

Where did you hear the EGC did that? IF there is noise and crap it is carried by the circuit Hot and neutral current carrying conductors.

The insulation covering building electrical wiring has a 600V rating. The insulation does not prevent magnetic fields created by a current carrying conductor from passing through the insulation. The purpose of insulation is to safely contain the HOT voltage potential from passing through the insulation to another HOT conductor, or a grounded object, or the neutral, the grounded conductor.

If you are looking for insulation on the bare EGC in Romex the bare conductor is wrapped in an insulating paper material and is encased in the outer non conductive PVC jacket of the Romex cable.

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Quote from the late Henry Ott:

Grounding Myths

"Electromagnetic Compatibility Engineering" by Henry Ott

3.1.7 Grounding Myths

More myths exist relating to the field of grounding than any other area of electrical engineering. The more common of these are as follows:

1. The earth is a low-impedance path for ground current. False, the impedance of the earth is orders of magnitude greater than the impedance of a copper conductor.

2. The earth is an equipotential. False, this is clearly not true by the result of (1 above).

3. The impedance of a conductor is determined by its resistance. False, what happened to the concept of inductive reactance?

4. To operate with low noise, a circuit or system must be connected to an earth ground. False, because airplanes, satellites, cars and battery powered laptop computers all operate fine without a ground connection. As a mater of fact, an earth ground is more likely to be the cause of noise problem. More electronic system noise problems are resolved by removing (or isolating) a circuit from earth ground than by connecting it to earth ground.

5. To reduce noise, an electronic system should be connected to a separate “quiet ground” by using a separate, isolated ground rod. False, in addition to being untrue, this approach is dangerous and violates the requirements of the NEC (electrical code/rules).

6. An earth ground is unidirectional, with current only flowing into the ground. False, because current must flow in loops, any current that flows into the ground must also flow out of the ground somewhere else.

7. An isolated AC power receptacle is not grounded. False, the term “isolated” refers only to the method by which a receptacle is grounded, not if it is grounded.

8. A system designer can name ground conductors by the type of the current that they should carry (i.e., signal, power, lightning, digital, analog, quiet, noisy, etc.), and the electrons will comply and only flow in the appropriately designated conductors. Obviously false."

Henry W. Ott

Who is Henry Ott?
Henry W. Ott | IEEE Xplore Author Details

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