Installation of new AC lines......best way to ground to avoid loops and noise

brayeagle211 posts

03-20-2019 10:56pm

My two 20 amp dedicated circuits were installed by a licensed electrician, then checked by the City’s Code Inspector.
Why? Homeowners Insurance, City requirements, Warranty for the work, and Peace of Mind.

I’m a very senior (Old Fud) retired electrical engineer. I could have done the work, but understood my current knowledge of the Codes was not up to snuff. Inadvertent mistakes can be costly.

National Electrical Code 90.1 Purpose:

(A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.

B) Adequacy. This Code contains provisions considered necessary for safety. Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.

FPN: Hazards often occur because of overloading of wiring systems by methods or usage not in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of electricity. An initial adequate installation and reasonable provisions for system changes provide for increase in the use of electricity.

(C) Intention. This Code is not intended as a design specification or instruction manual for untrained persons.

(D) Relation to Other international standards . The requirements in this Code address the fundamental principles of protection for safety contained in Section 131 of International Electrotechnical Commission Standard 60364-1, Electrical Installation of Buildings.

FPN: IEC 60364-, Section 131, contains fundamental principles of protection for safety that encompass protection against electric shock, protection against thermal effects, protection against overcurrent, protection against fault currents, and protection against overvoltage. All of these potential hazards are addressed by the requirements in this Code.

Look Closely at Section (B) Adequacy it reads as follows: "Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electric use."

First, let me be clear that my intention is to not, I repeat not, get into arguments about the technical aspects (or non-technical) aspects of having your system wired on both voltage legs.

I am an Electrical and Electronics Engineer, well versed in amplifier/filter design and test.  I am also a power Engineer and a state registered power Engineer.

I don't have the in front of me but it is safe to say that in designing home electrical circuits, the Electrician tries hard to balance the house loads on each phase so as to not overload one phase.  So, air conditioners, refrigerators and equipment with large current load are balanced between the phases.

For high end audio equipment, the low level equipment isn't an issue.  However, for ridiculously large class A amplifiers or some such, that is another issue altogether.  If the Electrician has half a brain, he/she is going to inquire as to average load usage and try to balance that load.

This is a non-issue.  What is the issue is to try to not have audio equipment on the same circuits/legs as noisy equipment, such as particular types of lighting.

Ground loops are created by potential (voltage) differences between equipment on a closed loop, which will cause current to flow in that closed loop.

AC from the panel is converted to DC in most audio equipment, so which leg it comes from is really a non-issue.  As long as the ground and neutral run back to the panel and are not shared.  When you share neutrals or the grounding scheme of your system or worse, of a particular piece of equipment is not well designed, that is when you have serious problems.

This is why I tell people when running dedicated lines to make sure each dedicated line consist of a hot, neutral and ground that is run directly back to the service panel with its own circuit breaker and are not shared.

So, say one has two amps and a lot of low level electronics, then ideally, you would want a minimum of three dedicated lines to the panel.  One for each amp and another for the low level equipment, such as pre-amp, tuner, cd player, DAC, turn table, etc.  That I recommend all low level equipment is plugged into a power conditions (tying the grounds together) and that has its own dedicated line.

My ground flow is seriously low. When I installed the dedicated lines, the ground flow dropped to dead silent.  Playing with various power conditioners for the low level equipment was fun as the sound improved with better conditioners. 

Again, most ground loops are caused by voltage imbalances between equipment and seriously poorly designed grounding schemes within equipment.  most newer equipment has a type of star grounding schemes within the equipment. 

If it isn't a loading issue on your panel, then yes, why not?  go ahead and put all equipment on the same leg.  But, it isn't the end of the world.  That is not a ground loop problem.  Also, it is quite easy to move that circuit or circuits to the other voltage leg within the panel if need be.  But, I doubt it is a real concern.

enjoy

Sigh;  Spell check. 

1.  I don't have the NEC in front of me.

2.  My Ground floor noise level is seriously low. 

enjoy

Ground loops are created by potential (voltage) differences between equipment on a closed loop, which will cause current to flow in that closed loop.