Grounding bar for audio/video racks...

[Externet]

Hi.
Installing a substantial amount of professional equipment in half a dozen racks, there is copper grounding buss bars among the items.

I thought I had it clear, but cannot discern its proper use. Please help.

The bars are BB-40 : https://www.avalive.com/Middle-Atlantic/BB-40/15627/productDetail.php

And I installed them exactly as per their enclosed instructions. The part I do not get is they are isolated from the metal rack by nylon washers. The link above shows the insulating plate and shoulder washers for the fastening hardware.

The energy is the standard 120VAC phase, neutral and ground.
The floor is metal; the room walls are a Faraday cage, in a concrete building; grounding rods are hooked to the room floor, roof and walls.

What is the usage of such buss bars ? All equipment has its proper 3-prong plugs to the outlet strips; all cabinets are metal, attached to the grounded metal racks.

 

[nsaspook]

https://en.wikipedia.org/wiki/Ground_(electricity)#Electronics

"technical ground"

 

[Externet]

Thanks.

Borrowed from the wikipedia link above :

..."Separating low signal ground from a noisy ground

In television stations, recording studios, and other installations where sound quality is critical, a special signal ground known as a "technical ground" (or "technical earth") is often installed, to prevent ground loops. This is basically the same thing as an AC power ground, but no appliance ground wires are allowed any connection to it, as they may carry electrical interference. In most cases, the studio's metal equipment racks are all joined together with heavy copper cables (or flattened copper tubing or busbars) and similar connections are made to the technical ground. Great care is taken that no AC-grounded appliances are placed on the racks, as a single AC ground connection to the technical ground will destroy its effectiveness. For particularly demanding applications, the main technical ground may consist of a heavy copper pipe, if necessary fitted by drilling through several concrete floors, such that all technical grounds may be connected by the shortest possible path to a grounding rod in the basement."...

From the highlighted above:
Great care is taken that no AC-grounded appliances are placed on the racks ---> Then I should not use the bars ?

no appliance ground wires are allowed any connection to it ---> The wiring shields are internally connected to patch bays chassis. If I connect the shields to the copper buss bars, I would be joining the bars to racks and equipment chassis.

More light please. Is it possible the bars were wrongly ordered for this setup ?

AC 120v Phase
AC Neutral
AC ground------------------------------------------------------------------------connected to Faraday cage, ground rods, racks and equipment cases.

Isolated copper buss bars in each rack--------------------------------------------------------Connect to ??

Zillion shields from wiring -----------------------------------------------------Connect to those isolated copper bars or to equipment chassis ??

 

[ronsimpson]

Grounding is something we can fight about for years. Every one has examples of good and bad. What worked for one person will not work for another.

Star: I have worked in broadcast/recording locations where star grounding was used. Every piece of equipment was isolated from the rack and all other equipment. Every wire from each control room went to a central location to be grounded. There are huge bundles of wire running to the center point.

I have never built a sight like that. I usually connect each piece of equipment to the rack and each other as well as I can. I use braid or strapping to connect each rack. Then I connect each room with 4" wide braid. By not running the wires into another room and back I believe I don't need as good a grounding system.

I believe the ground needs to either be smart like the star or it needs to be strong with very low resistance. Neither smart or strong will be a problem.

Usually I spend some time trying to get the power to run in the same pattern as the audio and video wires. While I would not run audio and 110/220V in the same bundle, I would run then 2 feet apart in the same direction.

 

[nsaspook]

Thanks.

From the highlighted above:
Great care is taken that no AC-grounded appliances are placed on the racks ---> Then I should not use the bars ?

no appliance ground wires are allowed any connection to it ---> The wiring shields are internally connected to patch bays chassis. If I connect the shields to the copper buss bars, I would be joining the bars to racks and equipment chassis.

More light please. Is it possible the bars were wrongly ordered for this setup ?

The technical ground is star connected (on a seperate wire) back to the main station ground point as is each AC rack ground. All grounds related to AV signals (zillion of shields) but NOT power or chassis/rack ground points are terminated on the isolated buss bar. The technical ground buss bars can be daisy-chained to the next isolated ground bar from rack to rack if they are next to each other. Most of my station work was in TEMPEST certified locations that used "technical" grounding on the RED side of the house (patch bays jack grounds were isolated from the mounting plates and connected only to the technical ground not the rack ground).

This is something that should have been in the build plan long ago if it was a true requirement with the correct switching equipment specified for this option.

https://www.electro-tech-online.com/custompdfs/2012/01/SurgeXPowerGround.pdf