Isolated Ground.......

[mbrooke]

Let me start off with saying I think IGs are a waste of time and materials in almost all cases.

I only install them because I am paid to install them.

Why only 'dated audio equpment' what has recently changed?

Dated electronics in general. Todays equipment tends to be less bothered by dirty grounds and EMI in general both because of digital processing and the fact manufacturers know clean grounds are impossible in all cases.

As do I.

:thumbsup:

And that can cause issues on audio lines yes?

Yes. But in a case like that only true IGs (isolating the equipment from all other grounds) would work. Isolation transformer might be another option too.

Another news flash, thanks. (Not trying to be disrespectful, just having some fun)

I know, just making sure we are on the same page

The above is one of the top reasons I think IGs are a waste of time. In most circumstances they often become compromised soon after completion.

100% agree, I see it the same way.

I have yet to see anything more than opinions on what a 'true IG is'. I sense your definition is pretty narrow.

IMO a true IG is 1. done to code, and 2 the equipment is on rubber supports and isolated 100% from an ground. However, that is my opinion only.

Yes, but that is not the only reason and you can have a dirty ground. Your position seems to be that only code violations induce hum on audio lines. I disagree. Any AC current flow on the shild between audio equipment can be a problem and IGs can sometimes help to reduce that current.

I agree, other conditions can do it to perfectly within NEC & UL, but in many cases the biggest contributor if not the only one is current on the grounding system from wiring faults/errors.

You are correct, ANY current flow on a shield will cause problems, but only a TRUE iso ground may solve that. As soon as you touch equipment without an ISO ground you loose that first iso ground.

Do you have a source for this or is it just what you have decided?

I have to dig up the sources, but from reading on audio noise and seeing real world issues IMO its apparent. Ditto for people lifting the ground.

And I still disagree with that assessment.

Depends on the building and things plugged in. My point is you could have a room where only micro amps, ok a few milliamps are on the ground system. But as soon as branch noodle is grounded that current will spike to amps.


Im not saying that is the only cause of ground loops causing noticeable problems, rather the majority. I should have worded it better. But its safe to say that in any case where ground loops exist in a code wired building that as soon as you start putting neutral current on the ground, what ever problem you had, will get many times worse.

I am not 'skeating' around anything. I simply disagree with your position that the only cause of ground loops are code violations.

More in depth you do have a valid point. Do you have any examples (real world cases) of what can cause ground loops (ie, building was found with many occupancy sensors)?


Definitely not saying you are wrong, you are correct, but just wondering what else can cause nuisance ground currents.

That is not factually correct. Simply connecting your CATV, SATV, or aerial antenna creates a loop. Interconnecting audio device with ground referenced signal inputs creates loops. All those interconnections fully comply with NEC requirements. No IGR can fix it or remove the problem, most likely is does nothing or make it worse

My apologies, I guess I was using the terminology to vaguely and improperly :ashamed1::ashamed1:


By ground loops I do not mean parallel ground connections. Those are impossible to avoid and in truth beneficial even necessary.

When I was using the term 'ground loop' my intent was not to describe parallel conductive paths, rather to describe excessive objectionable current on those paths. IE, dirty ground, ground currents and ground voltage differences.


This is what I meant by ground loops, aka dirty ground:

1. http://ecmweb.com/site-files/ecmweb.com/files/archive/ecmweb.com/nec/code-basics/107ecmCBfig2.gif

2. http://www.diychatroom.com/attachme...en-ground-objectionable-current-mike-holt.jpg

Move into a commercial or industrial installations and the whole building has thousands to millions of ground loops. In those installations the building is made from steel and concrete and every place you attach conduit, junction box, machinery, makes contact with the structure you have a loop. No amount of IGR is going to fix any of that.

Of course, its literally a giant faraday cage.

Like I said earlier IGR today is a 8-track tape issue and completely antiquated because today almost no signal interconnects today use unbalance signal transmission they use ground as a signal path. If you have some relic equipment using something like RS232, you do not use IGR to fix noise problems. You get you a pair of optical isolator and fiber cable to replace the antiquated copper signal cable, or convert to Ehternet or some other form of Balanced Signal transmission.

Today in a modern Telephone Offices, Data Centers, Cell Tower, and Communication Centers the whole building is designed to be a massive ground loop where you intentionally bond everything together with copper straps. It is called MESH GROUNDING. Some of the equipment is required and installed on steel diamond plate decking on a raised platform. Next time you drive by a cell tower and the carrier uses outdoor equipment take not it is on a raised platform of steel. They are constructed much like a electrical sub-station. That raised platform is bonded to earth every 4 to 6 feet and each corner to another underground grid type GES. The whole purpose of doing this is forming a Equipotential Ground Plane where the impedance between any two points is practically ZERO. So any currents that might be passing through it does not produce and significant voltage including lightning fault current

.


All true.

Ground Loops are good thing to have if you know what you are doing. Single Point Ground can be used, but is easily compromised even following NEC requirements

Grounds loops or in your case parallel conductive ground paths are a good thing if not essential. The issue is only when to much stray 50/60hz (and other) currents are on all those parallel paths.

It was this stray current that was making people try to break from the grounding system, ie lifting the EGC and driving a ground rod.

My apologies for using the terminology poorly. :ashamed1:

 

[jmellc]

I don't follow the logic of the skeptic. I was taught to do IG's by using 12/3 wg MC or 2 grnds in hard pipe. 1 ground to recept, isolated & 1 ground to the box/raceway. Equipment and raceway both protected that way. They also make specific IG AC cable now too, and maybe MC. i just don't see where this is a problem.

 

[mbrooke]

I don't follow the logic of the skeptic. I was taught to do IG's by using 12/3 wg MC or 2 grnds in hard pipe. 1 ground to recept, isolated & 1 ground to the box/raceway. Equipment and raceway both protected that way. They also make specific IG AC cable now too, and maybe MC. i just don't see where this is a problem.

Teaching is nothing more than passing along someone else's ignorance, a student is one who blindly accepts what is being said. Ok in terms of IGs:lol: I kid in a nice way



Its a waste of copper, and if anything raising the low impedance fault clearing path while bypassing equal potential in super technical anlysis terms. Id be meggering the circuits first before even thinking of IGs.


I know some manufacturers recomened IGs like cash register makers, but to be honest its no different then generator manufactueres requiring a ground rod for a none SDS genny. Its not required by code, its not doing anything useful, it looks really sexy, but under electrical theroy it actually may do more harm than good. A volatge gradient across the earth can be picked up between the genny ground rod and the service ground rods. Ok, those arent my words, they are Mike Holts, but you get the picture.

 

[cuba_pete]

IG's Work if Used Properly

IG's Work if Used Properly

This conversation always goes round and round. People will call "Isolated Grounds" crap and say they don't have any use.

Whenever an electrician shows up in my facility to do work (EE, Apprentice, Journeyman, Master, Administrator, Contractor, whatever...) We usually end up going to the mat about our single point ground.

My facility uses IG receptacles as part of a system. For decades in literature our system was identified as an "Isolated Ground". Truth in fact the system we use is a single point ground.

We use a single point ground primarily because we feed power to a high voltage DC system which uses its own anode field. the SPG in the facility has 23 mA difference of potential between it and the (other ground) anode field. The two cannot be tied together for the all important feat of keeping any of the line frequency (or any of its harmonics) noise out of the processing equipment. There is a vast array of lightning and surge protection in place between all points.

The design minimum for processing is -200dB. Using the same reference, the quietest SPG reading I have found in the facility is -90dB. The issue I fight is to keep that 110dB (SNR) out of my processing. There are differential inputs to the processing equipment, and with the effective use of filter networks the shielding for all of the data cables is bonded to the SPG.

Yes, all equipment is isolated from all grounding (bonding) except at one point, the EGC, which is bonded in accordance with the NEC. Everything is on the up and up with all recommended methods in FIPS 94, IEEE Emerald, IEEE Green, IEEE Orange, and any other color of book or standard that is out there.

If you do it right, it makes a difference for those who really need it. Yes, it's hard...but that's my job.

 

[don_resqcapt19]

...
If you do it right, it makes a difference for those who really need it. Yes, it's hard...but that's my job.

I think that is one of the key points, there are not too many installations that "really need it" any more. And of course "doing it right" is another key point, and often it wasn't done right, equipment manufacturers often asked for an isolated ground that had no connection to the electrical grounding system.

 

[mbrooke]

If you do it right, it makes a difference for those who really need it. Yes, it's hard...but that's my job.

I agree 100%. There are two keys to this: Doing right which requires both intense code knowledge and electrical theory; and second only in applications that need it. Some ultra specialized laboratory test equipment may require it and your application as you mention it. If I saw your predicament I would say, yes, an diso ground when done to the book (as you have) is useful and worth the investment.


But everything outside of that just forget about it. Especially the hacked up IGs going to random unbounded ground rods in every other IG building around here :happyno:


Somewhat off topic but you hit another nail on its head. Single point grounding is key both for IGs and systems in general. Mike Holt did a vid which he said that studies were done showing that driving extra grounds at machines in addition to NEC required rods were actually a risk over an advantage since voltage gradient across the earth during lightning strikes and downed lines but current through the grounding system.

I think if the myth is debunked that electrons seek ground a lot will change for the better.


Starting at 13.35 why multi point grounding can damage electronics:


https://www.youtube.com/watch?v=qNZC782SzAQ