Installation of new AC lines......best way to ground to avoid loops and noise
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jsautter
Read pages 5 through 39. https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf . |
millercarbon443 posts @ millercarbon , Please read pages 31 through 36. https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf In most cases where the building electrical branch circuit wiring is the cause of ground loop hum it is due to the type of wiring used and or the type of wiring method that was used. I have two 20 amp branch circuits, (10-2 with ground Romex), that are 75ft each for my 2ch audio system. My audio system is dead quiet. No ground loop hum whats so ever. No difference of potential, voltage, between the two equipment grounds measured at the wall duplex outlets. Jim . |
@ jsautter Mother earth does not posses some magical, mystical, power that sucks nasties from an audio system Grounding Myths From Henry W. Ott’s big new book "Electromagnetic Compatibility Engineering" 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 |
brayeagle211 postsAgree 100% But in case you didn’t know the NEC (National Electrical Code) is bare minimum electrical safety code. You can exceed the bare minimum requirements of the NEC, you just can’t go below the minimum safety electrical standards, requirements, of the NEC. National Electrical Code 90.1 Purpose: 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. .. |
@minorl First you have a mighty fine 2ch audio system there. As for your statement stating that dedicated circuits installed to feed an audio system installed in a home must be fed from both 120V Lines, Legs, is not accurate, imo. Would you please cite in the NEC where it says it. In probably the majority of audio systems in the US and Canada the total combined load of the audio system equipment at best would add up to 8 to 12 amps continuous load at best. One 120V 15 amp branch circuit would be more than enough. Not to mention it would meet or exceed the bare minimum NEC standards. (#14awg copper wire fed from a 15 amp branch circuit breaker.) If the home owner wanted the electrician to install two 120V 20 amp dedicated circuits fed from the same Line, Leg, I see nothing in the NEC that says it would violate the the NEC. In your case with your audio equipment I can see and would agree the ARC mono amps should be be fed from both AC Lines, Legs. Yes, to balance the two loads across both Lines of the electrical service panel. Jim |
minorl said: Ground loops are created by potential (voltage) differences between equipment on a closed loop, which will cause current to flow in that closed loop.We are in agreement there. IF there is a difference of potential between the equipment grounding conductors of more than one circuit feeding audio and or video equipment, that is connected together by wire interconnects, there will be current flow through the chassis, signal ground, of the interconnect connected equipment . No different than when a difference of potential exists between the shield on an improperly grounded CATV providers coax cable and the equipment grounding conductor of the branch circuit outlet the audio/video equipment is plugged into. This guy is a well respected EE. https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf Jim Edit: @ minorl , you can edit your post by clicking onto the sprocket looking symbol below your user name and posted message. . |
Competent grounding of audio equipment isn’t that hard, despite the crazy amount of nuance that exists in this topic. IOW if your house AC wiring is done to code you **should** not have any problems; if you do its not the fault of the AC wiring. The NEC is bare minimum electrical safety code. From NEC Article 90.1 Purpose: 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. The NEC could care less if a person has ground loop hum problems with their audio system. The NEC’s only concern is the AC power feeding the equipment is electrically safe to protect persons and property from an electrical hazard. Example The NEC allows multiple branch circuits to be installed in a common conduit. Are the chances of ground loop hum greater using this type wiring method than using individual runs of 2 conductor with ground metallic armor MC cable? Yes, it is. Both type of branch circuit wiring meets the NEC. Individual runs of NM sheathed cable (Romex) installed correctly is better than using conduit with multiple single conductors pulled loosely, randomly, as is the normal installation method used by licensed electricians. Please read pages 31 through 36. https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf . |
