Sharing ground wire between two dedicated circuits

This is the most confusing thread I’ve ever read in my entire life. No wonder hi-fi interest is diminishing after reading all this.

Many audio-enthusiast’s, who previously didn’t know anything about audio equipment, and the interconnection between it, think that just by spending tens of thousands of dollars on the best audio equipment, should automatically make them know everything about AC power, audio equipment, and how to hook it up (and make them an audiophile). Not always the case.

There are simple answers to simple questions

Correct, but your questions are not simple ones, so they take some explaining. Yes, it can be frustrating for some.

This is the most confusing thread I've ever read in my entire life. No wonder hi-fi interest is diminishing after reading all this.

There are simple answers to simple questions and yet it seems so damn complicated. Clarity of communication Via simplicity is true genius.

@ditusa

​Nothing wrong with Non Metallic cable AKA Romex, in my opinion

If your power is isolated from all RFI.

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.

/ / / / /

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

.

@fuzztone Wrote:

I would never waste any money on Romex.

Nothing wrong with Non Metallic cable AKA Romex,  in my opinion, steel  armored Metal Clad cable, with steel receptacle boxes is better for dedicated audio circuits. Example: better shielding from electric fields and radio frequency interference.😎

Mike

@emergingsoul 

You may find some of this information useful:

Power Distribution and Grounding for Audio

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???

fuzztone

... connecting grounds any where besides earth creates a ground loop.

It’s not clear what you’re trying to say. A ground loop occurs when there are two or more paths to ground at different potential (voltage). You can have a dozen ground paths and if they’re all at the same potential you’ll have no issue.

In the US, a residential system’s safety ground will be bonded to the service panel’s neutral buss bar, which is also bonded to the electric utility’s neutral.

Ground Connects to a stake in the dirt, why don't you like romex?

I would never waste any money on Romex. An connecting grounds any where besides earth creates a ground loop.

Here you go.  This is the best treatise on wiring for AV/2-channel audio that I have seen.  Basically, it is the wiring scheme I have used for years.  This works.

@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...

/ / / / /

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.

.

@emergingsoul If you’re going to spend this kind of money for two dedicated circuits, why not just spend a tiny bit more for the best? If they are truly dedicated circuits, with dedicated circuit breakers, their grounds should both never intercept with each other, until they reach the circuit breaker box (aka load center). Instead of using Romex, go a step further, and use Aluminum Armor Clad for Healthcare Facilities (AC-HCF). It’s the absolute best choice for Isolated Ground A/V systems. The biggest benefit is that the average proximity of the hot conductor and the neutral conductor, with respect to the isolated equipment grounding conductor, is nearly equal, virtually eliminating ground voltage induction (GVI), even on long runs. If you go that (AC-HCF) route, I’d also use isolated ground outlets.

gs5556, amazing answer thank you

Is Romex 10/3 good for the dedicated Circuit?  I was told the ground was insulated, which seems like a good idea. True?

I was also told 10/3 better to use vs 10/2, because the ground is insulated and 10/2 is not. So it's all a bit confusing

As long as both circuits originate from the same panel you can share the ground -- if your jurisdiction uses NEC 2014 or later.

Note that 10/3 Romex has three uninsulated wires (black, white, red) and a bare ground, 4 wires total. The insulated red wire you are making a ground must be wrapped with green electrical tape where visible (in the outlet box, panel or any intermediary junction box).

If you are using metal boxes, you can use the bare ground clipped/screwed to the 10/3 box and the insulated (taped green) conductor on the 10/3 receptacle ground screw. You can then tie the 10/2 ground from the 10/2 receptacle (or metal box ) to the 10/3 box.

If plastic boxes, then run the #10 insulated "ground" from receptacle screw to screw and clip the bare grounds back to the orange insulation.

Functionally I think it is fine.  I don't know if it meets the code. Others will likely chime in.  If you are having an electrician install and a building inspector inspect you need to make sure both of them are ok with it.