Star Grounding System Question

[Guest]

[quote][/quote]

Okay I get that but where is all of this going?

[alexidoia]

Hi there,
I realised that this post is now quite old but I have another question related to it.
Although I did get a lot of useful information this thread did not cover a part of the installation that is important to me.
I have the chance to have a separate ground system for my recording studio, and my question is this one:

Besides the safety instructions, is there some special things to do when burying the ground into the earth ?

I have been told many things as for example the metal stick must not go too deep in the ground or it can catch some electricity and take it back into the building. I have also been told about it directivity that must not be horizontal but perfectly vertical etc...

What can you tell me about this part of the grounding system ?
Thank a lot for your time here anyway.

Alex

[knightfly]

Alex, welcome; can you please edit your profile (top of the page) to include a location? This is a worldwide resource and we need to know which PART of the world our members are in, so we can provide info that is relevant to YOUR area - a LOT of things are different in different parts of the world; thanks...

Don't worry about "old posts" - this one is important enough to be "stickied" so people can find it.

It sounds to me like you've been told a few "fairy stories" about electrical - here is what the NEC says is OK to use for a ground electrode -

(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors.

(2) Metal Frame of the Building or Structure. The metal frame of the building or structure, where effectively grounded.

(3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (½ in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means.

(4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG.

(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.5 m (8 ft) in length and shall consist of the following materials.
(a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.
(b) Electrodes of rods of iron or steel shall be at least 15.87 mm (5/8 in.) in diameter. Stainless steel rods less than 16 mm (5/8 in.) in diameter, nonferrous rods, or their equivalent shall be listed and shall not be less than 13 mm (1/2 in.) in diameter.

(6) Plate Electrodes. Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil. Electrodes of iron or steel plates shall be at least 6.4 mm (1/4 in.) in thickness. Electrodes of nonferrous metal shall be at least 1.5 mm (0.06 in.) in thickness.

(7) Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems and underground tanks.

(B) Electrodes Not Permitted for Grounding. The following shall not be used as grounding electrodes:
(1) Metal underground gas piping system
(2) Aluminum electrodes

The preceding is from NEC 2002.

Newer residential buildings in the USA are typically using the concrete encased electrode method, simply a full-length piece of re-bar with a copper wire clamped to it and run to the electrical box.

Hope this helps... Steve

[alexidoia]

Thanks a lot!
I take from there that besides the norms there is no much else to do to do it correctly then.
I have read your enigma document and it is very interesting.
As you can now see on my profile I am from the south west coast of France at the Spanish border. There, we have 220V tension with a hot/neutral and ground wire (I think). What are my possibilities if I want to have balanced power ?
Thanks
Alex

[mistertones]

Talking to our electrical installers, it seems that in our setup a star earth will be relatively straightforward, but that a dedicated earth for the studio could be much more complicated - and installing an entirely separate supply for the studio isn't an option.

So, my question is, are the advantages of a star earth wasted if we don't have a dedicated ground ? Or, is it still worth doing anyway ? I'm imagining the answer is yes...?

Thanks for any insight !

Ian

[knightfly]

Ian, a separate, dedicated ground (but bonded to other ground system, which is MANDATORY) will probably give slightly better noise floor, but with or without you'd still see the least amount of noise when ALL your gear sees one common ground point - this is true, even if you're on the 27th floor of a building and are tied to a ground bus wire that runs all the way from the basement. The main thing is that (a) there is only ONE ground point, and (2) only one PATH to that point from any piece of gear.

Note that I'm not saying this would be AS GOOD as being on the ground floor with a heavy, short wire running directly to a proper ground electrode - odds are it's NOT. But the single point for every item in your studio to get its ground will ALWAYS be better than several separate runs to a remote point.

Hence the comments elsewhere about telescoping shields, isolated chassis, etc - the minute you have more than ONE WAY to get to the ground, you have a LOOP (spelled A-N-T-E-N-N-A...) Steve

[alexidoia]

Steve,
Thanks a lot for this.
I will see with my electrician what I can do and will make sure I do a Start Grounding system even if I must connect it to the main grounding pipe anyway, the good thing is that that main pipe goes through my garage before going into the groud. I simply have to make sure it is at least 3m into the ground.
But how could I install a balanced power system ?
Thanks
Alex

[mistertones]

Ian, a separate, dedicated ground (but bonded to other ground system, which is MANDATORY) will probably give slightly better noise floor, but with or without you'd still see the least amount of noise when ALL your gear sees one common ground point - this is true, even if you're on the 27th floor of a building and are tied to a ground bus wire that runs all the way from the basement. The main thing is that (a) there is only ONE ground point, and (2) only one PATH to that point from any piece of gear.Steve

Thanks Steve, that's what I hoped. Star-earthing it shall be !

Ian

[knightfly]

Balanced power - these are the guys who were instrumental in getting balanced power added to NEC a few years ago -

http://www.equitech.com/

check out their FAQ and white papers, there's a LOT of info there... Steve

[Velvet Elvis 2]

Being a dumb-computer guy and not an electrician, I am trying hard to reconcile this sticky with what has been proposed for my basement.

Here's the scenario... the house has a sub-panel located in the basement that is a 40 amp service off of the main panel. There will not be any air-conditioners, stoves, fridges, dryers etc on the sub-panel, but they are connected to the main panel.

The electrician (in talking to him about noise) has said that "what he's always done is run isolated ground outlets with homeruns back to the panel".

He suggests I find out which outlets in particular in the studio I want isolated, as to cut down on wire cost (because he can daisy chain the rest).

I am assuming that the isolate ground outlets in essence acts the same as the star ground because they would all share the same ground point (the grounding strip on the sub-panel) and would from there be bonded to the ground of the main panel which is required by code.

My thought is to run homeruns for everything because you never know which outlet you might suddenly need for audio.. but maybe I'm too paranoid.

What do you think? Does this sound like he is approaching it correctly or is there something I'm missing altogether?

Thanks,
Jim (Velvet Elvis)

[knightfly]

He has the right idea; IGR outlets are what's needed to do a proper star ground system, especially if it's run in metal conduit (conduits are supposed to be BONDED to the ground system, so a standard outlet in a metal box/metal conduit run can NOT be isolated - the FRAME of a standard receptacle is bonded to the ground terminal so the third prong of your plug would automatically be grounded to the conduit and earth, which makes it NON-isolated ground.

The IGR receptacles SEPARATE the third pin of the plug from FRAME ground, so a separate wire can be attached to the isolated ground terminal of the receptacle and run back to your common star point without creating a LOOP.

IGR's require 4 separate wires because of this - Hot, Neutral, Safety ground and Isolated ground - the Hot, Neutral and Safety grounds CAN be daisy-chained if on the same breaker, but the Isolated grounds must ONLY be connected to the common Star Point, regardless of where this star point is located. This is what makes the IGR's work - each ground pin of each receptacle has only ONE PATH to a COMMON point, so ALL of these isolated grounds are at EXACTLY the same potential because there is no (reasonable) chance of current flow in that isolated ground wire.

If you're running everything with Romex, and your boxes are plastic, then standard receptacles are OK - but this gets a bit tricky unless you go with 3-wire plus ground Romex and do home runs for EACH OUTLET back to your common star point, because code requires that any SEPARATE ground wires be run "in close proximity" to the other wires, and "protected" which can get interpreted by some inspectors to mean "conduit" -

The "close proximity" thing is to ensure that a dead short will trip the breaker quickly, and has to do with inductive coupling of all the wires involved - if your separate ground is running a different physical path back to the panel, this inductive coupling doesn't happen and a short can conceivably take too long to trip the breaker, increasing the possibility of a fire.

I'm of the same mind as you are; in a studio, there's a chance that ANY outlet could be used to power gear so I tend to make them ALL the same; same star ground, SAME PHASE. Dedicated lighting and other stuff can be put on the OTHER phase of your service to help balance loads.

I personally don't think "penny-wise and pound foolish" makes sense, especially when you'd have to destroy a sound-isolated wall to get at the wiring when you find out you shoulda done it better... Steve

[Velvet Elvis 2]

Steve,

It is all plastic boxes... so there will not be any conduit.

I'm confused about the 4 wires needed when using plastic boxes. Where does the 4th wire go, as the standard outlets I've seen have connections for hot, nuetral and ground.

I plan on homerunning all of the outlets back to the breaker box and somehow dealing with connecting them to the same circuits etc.

Jim

[knightfly]

Sorry, plastic boxes don't need the 4th wire, NOR do you need IGR's.

With home runs per outlet, just tie the three wires to the normal terminals at the receptacle and, at the panel, ONLY connect the bare ground wires to the common ground bus bar in the panel - Make sure ALL these runs tie their Hot wires to the same leg(phase), even if they're on different breakers - DONE... Steve

[Velvet Elvis 2]

Steve,

You ARE the man!

You just saved me lots of headache... not to mention money!

Thanks!

Jim

[chrisgraff]

Here's a link to a 6 page thread on RO where we thrashed this to death some time back - rather than regurgitate all of it, you can find pretty much everything you need here, including relevant code sections to show your inspectors, electricians, etc -

http://www.recording.org/posts16729-0.h ... highlight=

Grab a cup of coffee and some snacks, this will take a while... Steve

That link is dead.