star grounding questions

Hello, I am clueless on this one...I believe I have read most of the post here and other links....but I still am not sure I get it. In my present location...there are not any inforced electrical codes and good electricians are hard to find.... So I want to try to understand as best as i can. 1.when using a Star grounding scheme. Does ALL audio gear conect to this? guitar amps, mic pres, digidesigns 002, pa, mixer, furman power conditioner, outboard FX units, bass amps, etc...? 2. tracking room/rehearsal room and control room on the same Star grounding scheme run? 3. Should a separate Ground rod be installed that would have the Star ground scheme cable wired straight to it..bypassing the ground bar inside the breaker box that has an exisiting ground rod wired to it with all existing grounds tied to it?

I'm off to the races, but this is probably the best single source of intensive info on grounding audio gear - http://www.rane.com/note151.html I'll try to get you a basic diagram tomorrow some time... Steve

Thanks Steve, Goodluck at the Track! I remeber my days"where the Surf meets the Turf". I attached a semi..plan for outlet locations and audio cables...just in case. Have fun, John

John, sorry; that "off to the races" was figurative, not literal... If you've gotten a chance to read all the RANE link, here's another you may not have seen - http://www.johnlsayers.com/phpBB2/viewtopic.php?t=2206 Not sure what else I could add, and it sure saves me a crapload of typing... Steve

Right on Steve, I read it and copied the Starground diagram. Still not sure of a couple things. Maybe its right in front of me? but I still am not sure. 1. Does the ground end up at the bar in the breaker box that has all the rest of the houses grounds tied to? or do I install a new earth ground bar and run that to the breaker box and tie the audio (starGround) directly to that bypassing the bar al together? 2. What / where is the point that all the grounds from the audio outlets connect to...the center of the star? 3. Is it a good idea to run all my electrical from the cieling down and the audio cable from the floor up( through the cinder block of coarse.)? Thanks, John

The term "star" grounding doesn't actually mean it has to be SHAPED like a star; rather, it means NO LOOPS - so as long as your original ground bus is well connected to a solid ground rod, the only other electrical criteria is that each receptacle's ground pin is connected to ONLY ONE point, and that is your "star point" - IOW, one outlet, one wire from its ground back to the common ("star") point. Do NOT connect this wire to ANOTHER outlet on its way back to the star point, you must run ANOTHER wire from EACH outlet back to the common (star) point. No "daisy-chaining", no connecting extra wires between grounded outlets. As long as there is only one wire from each outlet's ground terminal, and each of these wires goes ONLY to the common ground, you're good. As I mentioned in one of the links, if your wiring is in CONDUIT, you will need to get IGR type receptacles; these have NO CONNECTION between their metal frame and the ground lug. Instead, the conduit, the metal electrical box and the frame of the receptacle are all "safety grounded" by being "bonded" to each other and to the common ground. Your actual RECEPTACLE ground, however, MUST be kept electrically separate from this BONDED assembly, and instead a wire is run from the ground terminal on the receptacle itself, ALL THE WAY back to the common ground point. If using "romex" type wire, you would need to do "home runs" for each and every outlet, so the three wires in each romex only go to ONE outlet, and there is only one ground connection which starts at the common ground point in your switch panel and stops at ONLY ONE outlet. An alternative is to use IGR type receptacles (Isolated Ground),Metal boxes, and use "3-wire plus ground" romex; use the black and white for normal hot and neutral, use the bare conductor for box ground, and use the red conductor (phase taped GREEN on both ends) for your Isolated ground, which STILL must ONLY connect at one end to the ground (third hole) terminal on your IGR receptacle, and the other end connects to the common ground bus. It is neither legal or safe to have separate grounds, they MUST be bonded together; all the STAR system does is to make sure that NONE of your technical power grounds have more than ONE PATH to that ground, so there is ABSOLUTELY NO CHANCE that any CURRENT can flow in your tech ground system, except in the event of a FAILURE. I know I've written a lot, but this really isn't as complex as it sounds - only one ground path per outlet, NOTHING shares that path, and ALL of these end up at the SAME point. That's star grounding. HTH... Steve

Hey Steve, Just read more of the converstation on the page (link) and some of my questions where answered. Sorry about that. I am going to read it over a couple more times to make sure i understand. Thanks, John

Cool; once you've done that, draw me a picture of what you're going to do so I know you have it right... Steve

Knightfly, So is it a total "no no" to loop the power from receptacle to receptacle but run a seperate ground wire back to the star ground? I was just thinking of a way to conserve on my wiring. Of course I may not be saving all that much. Tom

Your Hot & Neutral you can "loop" to other outlets, but each receptacle needs to have it's own ground wire going back to the panel.

No, that's fine as long as the ONLY ground your equipment power cords sees is one that comes directly from the STAR point and serves ONLY THAT ONE receptacle - looping the neutral and the hot wires won't cause current to flow in the ground. Without current flow, there can be no voltage drop, so therefore ALL points in the system that need to be at ground potential ARE, since you can't have a difference in potential (voltage) between two points that are connected If all that sounds like gibberish, it's because I'm just off from my first 12-hour graveyard shift and fading fast - if it's still unclear I'll do a diagrame and explain that way... Steve

Huh? :?: :?

Kinda what I thought; off to the last "dirty dozen", I'll start over in a day or two, sorry... Steve

Thanks! I understand pretty much what you are saying. It is good to know I can loop the power legs. I did not want to have breakers for every box nor did I want to try and gang a bunch of wires to each breaker. Thanks. Tom

Hello, I have been out of the loop for a while now..My best friend and Drummer passed away recently...so...I am regrouping.. anyways.. I will send a sketch of how we are planning to wire up the studio so that you see if I am on track. One question? I understand so far that each outlet (audio) will have it's own individual ground running back to the ground bar in the pannel allocated to Audio. Can all of the individual grounds(#12 cables) be ran in the same conduit? PVC Conduit. Thanks again!!! John

yes running your grounds in the same raceway(conduit) should be fine. just dont put audio and electrical wiring in the same conduit. in fact audio and electrical should be separated by at least 12 inches and avoid running them parallel if possible. as far as your star ground( we call it isolated ground) i am not so sure just running a separate ground from each outlet back to the panel and hooking it up with all the other grounds would do you any good. I personally wouldnt even call it isolated. an isolated ground has its own isolated buss connected to its own isolated ground rod. this ground rod needs to be at least 10 feet from any other ground rod. maybe i am way off base here but i find the isolated ground to be a little overkill. Is this going to be a full fledged commercial recording studio?

right on...I have all the audio comming from the floor up throght the walls and all electrical coming from the poured cement cieling down the walls. None of the Audio and Electrical share conduit nor run parallel. Some outlets do end about 12-14 inches away from a audio wall panel. Non comercial at this point. Running a new breaker box from the meter that will have only audio outlets connected and a seperate ground rod for the breaker Box. All lighting will be connected to an exisiting breaker box. thanks for the input! John

STOP EVERYTHING AND READ THE FOLLOWING - Rocktavian, you need to read the NEC before giving advice on grounding - you may get someone KILLED otherwise. NO JOKE. I normally don't cut and paste from info I've PAID for, for obvious reasons; but I'm going to make an exception here, just to CLEAR THIS UP and possibly SAVE LIVES - here is an excerpt from the NEC, pay particular attention to the LAST PARAGRAPH (in bold print) if the rest doesn't make sense to you - 250.6 Objectionable Current over Grounding Conductors. (A) Arrangement to Prevent Objectionable Current. The grounding of electrical systems, circuit conductors, surge arresters, and conductive non–current-carrying materials and equipment shall be installed and arranged in a manner that will prevent objectionable current over the grounding conductors or grounding paths. (B) Alterations to Stop Objectionable Current. If the use of multiple grounding connections results in objectionable current, one or more of the following alterations shall be permitted to be made, provided that the requirements of 250.4(A)(5) or 250.4(B)(4) are met: (1) Discontinue one or more but not all of such grounding connections. (2) Change the locations of the grounding connections. (3) Interrupt the continuity of the conductor or conductive path interconnecting the grounding connections. (4) Take other suitable remedial and approved action. An increase in the use of electronic controls and computer equipment, which are sensitive to stray currents, has caused installation designers to look for ways to isolate electronic equipment from the effects of such stray circulating currents. Circulating currents on equipment grounding conductors, metal raceways, and building steel develop potential differences between ground and the neutral of electronic equipment. A solution often recommended by inexperienced individuals is to isolate the electronic equipment from all other power equipment by disconnecting it from the power equipment ground. In this ill-conceived corrective action, the equipment grounding means is removed or nonmetallic spacers are installed in the metallic raceway system. The electronic equipment is then grounded to an earth ground isolated from the common power system ground. Isolating equipment in this manner creates a potential difference that is a shock hazard. The error is compounded because such isolation does not establish a low-impedance ground-fault return path to the power source, which is necessary to actuate the overcurrent protection device. Section 250.6(B) is not intended to allow disconnection of all power grounding connections to the electronic equipment. See also the commentary following 250.6(D). End excerpt. OK, once more - a STAR ground does NOT, NOT, NOT, mean that you eliminate continuity (connection) from your electronic gear to the main system ground - this is UNSAFE and, in most countries, ILLEGAL. A STAR ground ONLY means that you have ONE, and ONLY one electrical path to ground for each and every source of electricity in the facility. The ONLY purpose of a STAR ground is to ELIMINATE the chance of ground LOOPS, which are the major source of hum in an installation. The term, ISOLATED, when applied to a STAR grounding system, refers to special receptacles known as IGR - this stands for Isolated Ground Receptacle, and it means that the FRAME of the receptacle is NOT connected to the third, or GROUND, pin. The main purpose of IGR's is in a CONDUIT system, because a conduit system requires that ALL METALLIC RACEWAYS (conduits) be BONDED to the earth ground. If you do that, and you've used NORMAL receptacles, the FRAME of these receptacles (the part you screw to the outlet box) is BONDED to the GROUND terminal and therefore to the third hole in the receptacle. This, in combination with the BONDED conduit system, means that now you have TWO paths for the ground from that receptacle - the WIRE you connected to the GREEN terminal which runs back to the system ground bar, and the BONDED CONDUIT system consisting of the outlet box, the conduit, and the breaker panel/system ground. That will give you ground loops, because there are now two separate paths with a finite amount of resistance, which will act as an ANTENNA and pick up a small amount of line frequency, making your ground AT THE EQUIPMENT no longer ZERO VOLTS AC. The proper way to wire these IGR's in a BONDED conduit system, is to BOND the frame of the IGR to the outlet box (you screw it to the box normally) - this provides the SAFETY ground for the system, which is now one continuous conductor thru the conduit and back to the breaker box and system ground. Hot and neutral (black and white) wired the same as any other receptacle - may be looped thru to save wire, as long as you don't exceed # of outlets for wire/breaker size. ISOLATED ground lug on the IGR receptacle - this runs to, and ONLY to, the MAIN SYSTEM GROUND (the one your heavy bare copper wire connects to, usually with copper ground rods driven into the ground - newer code requires a minimum 20 foot #4 rebar embedded into concrete slab (if there is one) and brought out of the concrete for a ground point. What this all accomplishes is a technical power system with no ground LOOPS, but which is STILL SAFE and properly grounded. Read this as many times as necessary to understand each section, and if you STILL have questions ASK THEM - this is, literally, a matter of LIFE AND DEATH. Don't stop until you are ABSOLUTELY POSITIVE you understand... Steve

Steve, thanks as always for helping us all maintain "not dead yet" status. 8)

i understand what i was trying to say was that the extra grounding was maybe a little overkill for a closet studio. Most small time folks have had this same gear plugged into there normal garage and bedroom receptacles for months if not years. I just didnt see spending the extra time and $ on something not really needed. I am not saying by any means that you should eliminate the ground. I am just saying a normal wiring ( meeting code requirements) method would probably be sufficient for your standard Musiciansfriend recording studio setup. If ya got the time and money and knowledge then by all means do it full tilt. I havent wired any Major Recording facilities but all my gear was made to plug right into a standard outlet. I will not give out any more advice on wiring recording studios on this forum because it seems like i may be (umm whats the word im lookin for Construction Trash lol :lol: ) when it comes to the ins and outs of a recording studio. I am just here to learn and i will leave the advice to the experts. Call me when ya need to add some lights to yer barn. :D

The star ground does not add "extra" grounding, all it does is ensure that each outlet has its own direct path back to the main household ground. By doing this, one bad apple (like a malfunctioning amp) will not spoil the tree (by making current flow in the ground through your other outlets thereby adding noise)! Is it worth the extra effort....I dunno, but if you have lots of gear on different outlets, its not too bad of an idea, and really an extra wire per outlet is not that much extra work now is it? That said, how about muti-point stars? Do they meet code? Can I run a seperate ground wire from each recepticle box to an intermediate star point, and then buss that to household ground. This would be far more convenient for my installation...I can't see offhand how it could be any less safe than a conventional snaked ground, but I'm just a newbie at household wiring and don't know jack about the codes. Cheers, Kris

Sure, there is no reason a star point has to be located right at the main system ground point; only that it's a star point, and that it's only ONE star point. IOW, the criteria is that ALL power sources in the studio have ONE COMMON grounding point, and only ONE path to GET to that point. Here's a description of a proper grounding system for balanced power; but all the steps are also necessary for a NON-balanced power install where minimum noise is required - http://www.equitech.com/support/techgrnd.html HTH... Steve