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Thread: PS Audio Power Ports

  1. #16
    Senior Member Phil H's Avatar
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    Quote Originally Posted by hapy._.face
    Since most panels will tie in the ground and neutral on a shared bus with the true ground wire (solid copper core) exiting the house and buried deep in the ground (get it? ground?)- I always wondered what (if any) benefit would come from running a TRUE isolated ground line for your dedicated receptacle?

    ...from the receptacle- run a dedictaed copper core wire right through the walls and to the outside on a rod and drive it a good 6' in the dirt.
    You need the neutral attached to the the ground at the panel so the breaker blows. Otherwise, this can happen.

    Image from http://www.codecheck.com

  2. #17
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    Quote Originally Posted by Phil H
    You need the neutral attached to the the ground at the panel so the breaker blows. Otherwise, this can happen.
    Not according to the NEC. A quote:

    'The NEC says the insulated equipment grounding conductor for an IGR may originate at the neutral point of the power source, and it may pass through boxes and panelboards without termination, but neither configuration is required [Secs. 250-96(b), 250-146(d), 250-148 Exception, and 384-20 Exception].
    The NEC does not require you to run the insulated equipment grounding conductor for an IGR back to the neutral point of the power source. In some cases, running it to this point would be too difficult, impractical, or expensive. Thus, the typical grounding termination point for an IGR in an existing facility is the equipment grounding terminal at the panelboard that supplied the circuit.
    Per the Code, the grounding terminal for an IGR could terminate to the metal outlet box that contains it. The NEC doesn't dictate where you terminate the grounding terminal for an IGR — just that you terminate to an effective fault current path. Nor does the NEC require each IGR to be on its own dedicated branch circuit.'


    IGR= Isolated Ground Receptacle

  3. #18
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by hapy._.face
    I always wondered what (if any) benefit would come from running a TRUE isolated ground line for your dedicated receptacle?

    ...from the receptacle- run a dedicated copper core wire right through the walls and to the outside on a rod and drive it a good 6' in the dirt.
    Bad idea. It would be at different ground potential than the electrical system ground.

    Dirt is high impedance (relatively speaking).

  4. #19
    Senior Member Phil H's Avatar
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    Quote Originally Posted by hapy._.face
    Not according to the NEC. A quote:

    'The NEC says the insulated equipment grounding conductor for an IGR may originate at the neutral point of the power source, and it may pass through boxes and panelboards without termination, but neither configuration is required . . .
    The NEC doesn't dictate where you terminate the grounding terminal for an IGR — just that you terminate to an effective fault current path. Nor does the NEC require each IGR to be on its own dedicated branch circuit.'


    IGR= Isolated Ground Receptacle
    Yes, the NEC allows the isolated ground to pass through boxes, panels, etc. When I made that statement, I was not very specific and did not say which panel because it may pass through panels unlike a typical grounding conductor. But, your idea of a seperate ground rod does not provide an effective fault current path. The ground rod does not help with ground faults occuring in the premise.

    NEC 250.2 Definitions
    Efffective Ground-Fault Path. An intentionally constructed, permanent, low-impedance, electrically conductive path designed and intended to carry current under ground fault conditions from the point of ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground fault detectors on high impedance grounded system
    Ground Fault. An unintentional, electrically conducting connection between an ungrounded conductor of an electrical circuit and the normally non-current-carying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.

    From 250.4(a)
    (1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher voltage lines and that will stabilize the voltage to earth to earth during normal operation."
    (4)Effective Ground Fault Path . . .the earth shall not be considered an effective ground-fault path.

    I hope Rudy responds to your inquiries because he is much more qualified than I am to answer this question. For instance, I don't think you are allowed to terminate an equipment grounding conductor on the the grounded electode conductor or the electrode. But, I do not know.

    Edit: Also the section 250.146 on isolated receptacles that you mentioned says "the receptacle grounding terminal shall be grounded by an insulated equipment grounding conductor run with the circuit conductors."

  5. #20
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    I thought the concept behind isolated ground was to actually isolate the ground from the nuetral. Maybe grounding it independantly isn't advised; However, hooking it up with the nuetral on the same bus doesn't make sense to me- why is it called an isolated ground if you tie them together? It seems that you would get EMI and that sort of undermines the concept of audio grade receptacles. Also, in the hospitols- isolated grounds keep the ground away from the nuetral so that there is no interference with sensitive life support equipment. Right? Enlighten me, please...

  6. #21
    SteveW
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    Hummm...

    Rudy, excellent reply - thank you for your input. Is it possible that Scott's improvement is the result of a higher signal-to-noise ratio due to less resistance to ground. Less current on the ground loops? Sounds to me like balanced power would be huge for his application. What do you think?

  7. #22
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by hapy._.face
    I thought the concept behind isolated ground was to actually isolate the ground from the nuetral. Enlighten me, please...
    Read up the link I posted at #8. Grounds are always kept isolated from the neutrals, except at the service entrance, where they are always connected.

    "Isolated" grounds merely means they are not also connected to receptacle boxes, conduits, etc., as Rudy reiterated above....

  8. #23
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    Quote Originally Posted by Zilch
    "Isolated" grounds merely means they are not also connected to receptacle boxes, conduits, etc., as Rudy reiterated above....

    OK. Thank you.

    So, armed with this information- (I am dangerous ) It would appear that from this information:

    The NEC does not require you to run the insulated equipment grounding conductor for an IGR back to the neutral point of the power source. In some cases, running it to this point would be too difficult, impractical, or expensive. Thus, the typical grounding termination point for an IGR in an existing facility is the equipment grounding terminal at the panelboard that supplied the circuit.


    ....an audiophile receptacle would benefit from a dedicated subpanel. Correct?

  9. #24
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by hapy._.face
    ....an audiophile receptacle would benefit from a dedicated subpanel. Correct?
    Nope. Just more connections, circuit breakers, etc. in the path.

    Have a licensed electrician run a dedicated circuit from the main panel, or several, if the need is compelling....

  10. #25
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    Quote Originally Posted by Zilch
    Nope. Just more connections, circuit breakers, etc. in the path.

    Have a licensed electrician run a dedicated circuit from the main panel, or several, if the need is compelling........
    Hey- easy now!

    I have a master electrian here that says otherwise.

    A dedicated circuit would get me a subpanel, too. The cool thing about a dedicated subpanel is that according to the NEC- I don't have to run my ground back to the main panel for the IGR. Therefore- less EMI, etc.

  11. #26
    RIP 2011 Zilch's Avatar
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    Uhmmm, ground in the subpanel comes from the main panel, just like everything else....

  12. #27
    Senior Member Rudy Kleimann's Avatar
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    Quote Originally Posted by hapy._.face
    Hey- easy now!

    A dedicated circuit would get me a subpanel, too. The cool thing about a dedicated subpanel is that according to the NEC- I don't have to run my ground back to the main panel. Therefore- less EMI, etc.
    The big wire feeding the sub-panel right there beside the sound system would help things out a lot too, as I will explain below. However, I believe you DO have to tie the sub-panel ground to the primary source ground. I think you can drive a secondary ground rod and connect it to the sub-panel ground buss (I'll have to check the latest NEC Code Book to be absolutely sure), and that would give you a better, cleaner ground for noise-dissipation purposes. you can also drive multiple ground rods and bond them all together to lower the impedance to earth.

    But never, never, NEVER- bond the neutral to the ground in that sub-panel.

    The idea of the IGR is to have a direct, low impedance (resistance) path to the system ground and to remove other high-impedance conductors, like the conduit, junction box, metal-stud walls, and steel structure sitting on/in concrete from having any connection to the grounding system. The metal has lower conductivity than copper, and may have a poor path to ground. This means it can act like an antenna, picking up EMI or even emitting EMI from currents passing through it which only "dirties up" the ground connection at the point where a "normal" receptacle mounts to the j-box, often 100 feet or more away from the ground rod. The resistance of the ground wire itself becomes a factor here. If you are trying to "drain away" noise that exists in the steel conduits, j-box, metal studs. and building steel that measures 200 millivolts through your ground wire,what will end up happening is that your nice little preamps' metal case will be getting some of that "building noise" imposed upon it too, radiating that noise into the sensitive circuitry carrying or amplifying your beloved music. That is not what you want from your audio component. An Isolated ground receptacle would be grounding and draining away only the noise coming from your audio components, be it from inside that preamp or from the stray magnetic field or digital switching noise generated by the TV, DVD/CD player, or power amp transformer (to name a few examples).

    In wood homes with non-metallic j-boxes and wiring raceways (Romex instead of conduit), the IG receptacle in the wall is a moot point.

    The things to concentrate on in any case are:

    Tight, clean connections, on the hot, neutral, and especially on the grounding system, with as few joints (splices) as possible from the receptacle all the way back to the ground rod.

    Wrap the wire around the screw on the receptacle. NEVER use that cheesy spring-loaded rear wiring hole on the cheapo residential-grade receptacle for the hot or neutral. Better-yet, use commercial Specification-Grade, or hospital-grade receptacles instead.

    A direct, dedicated ground wire straight from the power receptacle to the ground buss, with nothing else connected to it except the receptacle.

    Bigger conductors, especially for longer wire runs.

    Noise suppression on the incoming power and at offending equipment running on the electrical system.

    Ensure that all the metal cases of the audio components are properly grounded.

    Relocation of sensitive, high-gain circuits (preamps, tuners, etc.) away from interference-producing gear (power amplifier transformers, digital audio/video gear, etc)

    Elimination/removal/replacement of audio cabling that creates ground loops among the connected components.

    A circuit run (hot and neutral or hot and hot, whatever the case may be) of #12AWG copper 90 feet long has enough resistance to cause a 5% voltage drop at the receptacle if the load requires 20 amperes of current. This means 120 volts drops to 114 volts at the receptacle when the connected equipment draws 20 amps. 5% is the maximum allowable per the NEC how many homes violsate this? Ever see the lights dim when you turn on that 1800 watt (15 amps at 120 volts) hair dryer in the bathroom?

    With 5% voltage drop at the receptacle, the neutral would have 3V with respect to ground (hardly neutral at this point ) and the hot would have 117V, with 114volts between them. The other three volts would be lost along the length of the wire due to the wires slight resistance itself.

    Upsizing to #10AWG extends this limit to about 150 feet; beyond that distance, #8AWG is required. Although the #12 wire can carry a 20 amp load without overheating, the connected equipment would suffer from a lack of available power at the end of that long run of wire.

    By the same token, the ground wire would keep the voltage of the offending interference at 5% of the ungrounded voltage- 200 millivolts ungrounded is still 10 millivolts at the receptacle -with the ground wire attached!

    Bear this in mind: if a signal level of 1Volt from your preamp will drive your amplifier to full power and create a sound pressure level of 120dB, then you can hear down to +/- 120dB softer than that. Following the rule that 20dB=voltage change of 10:1, then 1 microvolt at the amps' output is our lower threshold of hearing sensitivity. Pretty tiny. An SPL of 40dB would be produced by 100 microvolts to the loudspeaker, be it signal or noise(or hum). And that would only be an S/N of 80dB. We all know we can hear that.

    A typical amplifier multiplies the incoming signal by 35-40dB, meaning the same signal (or noise) that produces 40dB SPL is only around 1 microvolt presented to the amplifiers' input.

    A good FM tuner can tune in a station whose radio waves generate less than 1 microvolt on an FM antenna feeding it. Phono cartridges, particularly moving coils, generate miniscule voltage signals too. And then there are microphones... These tiny signals need a lot of amplification to get them up to a level high enough to drive the power amp.

    When you think about it, isn't it amazing that we don't have worse problems with noise and interference in our audio systems?

  13. #28
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    Thank you Rudy- very informative!

    This is exactly what I was referring to, but you said it best:

    I think you can drive a secondary ground rod and connect it to the sub-panel ground buss (I'll have to check the latest NEC Code Book to be absolutely sure), and that would give you a better, cleaner ground for noise-dissipation purposes. you can also drive multiple ground rods and bond them all together to lower the impedance to earth.
    ...it's also consistant with what my electrician buddy says. He also says that is exactly the way life support systems are set up in hospitals.

    I think using the PS audio ports (or any high quality IGR) under this set up will yield even better results.

    Take care

  14. #29
    Senior Member herki the cat's Avatar
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    true ground wire (solid copper core) buried deep in the ground

    [Revision # 2] to my reply:

    [quote __long gone__"hapy._.face;108233"] ="Since most panels will tie in the ground and neutral on a shared bus with the true ground wire (solid copper core) exiting the house and buried deep in the ground (get it? ground?). I always wondered what (if any) benefit would come from running a "true ground wire (solid copper core) exiting the house buried deep in the ground for your dedicated outlet." From the receptacle- run a dedictaed copper core wire right through the walls and to the outside on a rod and drive it a good 6' in the dirt. [quote/]

    To begin with "Isolated ground receptical terminology" applies 'only" to duplex outlets with ground lug floating and not connected to the metal brackets of the duplex outlet. Ce Tout.

    This subject of secondary, add on, ground stakes resurfaces from time to time. Forum Member: neanderthal , 4350A,L-220,L-150A sometime back, posted his experience installing a "secondary dedicated grounding system" in his home complete with pictures. For the benefit of those new to this subject, here is what i learned from my local Citi Code experts, some 60 yeas ago.

    "Underwriters Laboratories & the NEC Codes do not permit a voltage differential between "isolated ground" and the AC power intrance panel neutral & ground bus", which around here is grounded to some sixty feet of one inch copper pipe buried underground, terminating at the street in the city water mains.

    Be aware that the AC power cord connector "third pin"green wire" ground is strictly a "personel safety ground" connected only to the metal cabinet or metal chassis of each audio system component. RCA signal interconnect recepticals should be insulated from the chassis and metal cabinets to prevent ground loops and other problems. Some equipments also use a very high value "static drain" resistor between the metal cabinets and the signal low side circuit bus.

    Since "(6) milliamps,efficiently coupled like in a bath tub to a human being is leathal," Underwriters limits the total allowed current to (5) milliamperes maximum of all ground currents dumped into this green safety wire from any source, including AC power filters, surge supressors, etc. Note that some prestigious manufacturers use power filters with .05 mfd capacitors connected from the 120 volt AC high side to the equipment enclosure, which in case of enclosure grounding defects, results in charging the enclosure with 120 volts AC power. __Ground loops anybody__? Consider what will hppen to an RCA interconnet cable receptical grounded to such an enclosure during loss of earth ground.

    Underwiters Laboratoris & the NEC codes will allow the "dedicated seondary ground wire buried deep in the ground, "PROVIDED" , only if this grounding wire or stake is also connected to the AC power intrance panel neutral & ground with an incredibly heavy cable. Check your local Code requirements. Underwriters & the NEC codes have rigid specification concerning the grounding stake component & soil conductivity.

    Cheers herky the cat
    Last edited by herki the cat; 01-31-2010 at 09:20 PM. Reason: clean up

  15. #30
    Moderator hjames's Avatar
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    FYI - Hapy_Fez is no longer a member and hasn't been here in years ...

    Quote Originally Posted by herki the cat View Post
    [quote hapy._.face;108233] ="Since most panels will tie in the ground and neutral on a shared bus with the true ground wire (solid copper core) exiting the house and buried deep in the ground (get it? ground?). I always wondered what (if any) benefit would come from running a "true ground wire (solid copper core) exiting the house buried deep in the ground"[quote/]

    No need to wonder about it, hapy._.face;
    Cheers herky the cat
    2ch: WiiM Pro; Topping E30 II DAC; Oppo, Acurus RL-11, Acurus A200, JBL Dynamics Project - Offline: L212-TwinStack, VonSchweikert VR-4
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