Isolated ground

[RRJ]

Good morning, where can I find literature on isolated grounding system for noise reduction in electronics. I was asked to run an isolated ground from multiple small equipments to the electrical closet isolated ground plate where the communication system is hooked to.


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[RRJ]

Good morning, where can I find literature on isolated grounding system for noise reduction in electronics. I was asked to run an isolated ground from multiple small equipments to the electrical closet isolated ground plate where the communication system is hooked to.


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Does the equipment needs to be hooked up to an isolated ground receptacle per 250.146(D) and 250.96(B). I might be misunderstanding the sections. An old electricians here is telling me to cadweld to the isolated ground inside the building and I think he’s joking with me. In other rooms they have a ground plate at the room where the equipment is to the electrical closet to an isolated plate where the data rack is hooked to.


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[Strathead]

I have run in to that. It isn't an isolated ground that they are asking for. The sound guys don't understand the term. They are looking for a drain. It is a fight. You have to ground all metal current carrying parts per the NEC. You can ground them to an isolated ground, but that is a ground that is generated at the bonding point of the neutral and the ground. You can always run an additional ground wire from the case of a piece of equipment to a ground bar, but it can't replace the code required ground.

 

[infinity]

Back in the day we ran the IG though the panel to the building steel (a violation). As Strat stated it should be run to the service where the MBJ is installed or to a transformer where the SBJ is installed. Neither of those methods are required by the NEC.

 

[zbang]

RRJ- this comes up a lot on the forums here, and the usual opinion is that "isolated grounds" don't help sound problems. OTOH, if you're getting paid to install them... go for it.

As for installing a grounding block, that's a design issue and there's nothing in the code about how/were to do it. It still must be bonded, somewhere, to the existing GES, and can not substitute for a proper EGC.

That's enough TLAs for one post .

 

[RRJ]

I don’t know what the point is if all the other grounds they ran to that plate are inside Emt with bonding bushings bonded to the ground plate. They are Bonding their equipment along the way with concrete, metal frame or beams via pipe strapping.


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[zbang]

The point is that in most places, there isn't much point for these extra grounding systems- most audio problems are improper audio wiring*, not "bad grounds".

*usually by people who don't understand the underlying electrical principals

If you really want to get into the theory, go to one of the sources, Bill Whitlock-

https://www.jensen-transformers.com/wp-content/uploads/2014/08/generic-seminar.pdf

"Are EARTH grounds really necessary for low-noise system operation? Think about all the electronics in an airplane!"

 

[Little Bill]

The point is that in most places, there isn't much point for these extra grounding systems- most audio problems are improper audio wiring*, not "bad grounds".

*usually by people who don't understand the underlying electrical principals

If you really want to get into the theory, go to one of the sources, Bill Whitlock-

https://www.jensen-transformers.com/wp-content/uploads/2014/08/generic-seminar.pdf

"Are EARTH grounds really necessary for low-noise system operation? Think about all the electronics in an airplane!"

Don't you know they have dirt/earth in the bottom of the plane and a rod is placed there to ground to!

 

[infinity]

I don’t know what the point is if all the other grounds they ran to that plate are inside Emt with bonding bushings bonded to the ground plate. They are Bonding their equipment along the way with concrete, metal frame or beams via pipe strapping.

That's a waste of time but someone probably thinks that it's actually doing something.

 

[hbiss]

I don’t know what the point is if all the other grounds they ran to that plate are inside Emt with bonding bushings bonded to the ground plate. They are Bonding their equipment along the way with concrete, metal frame or beams via pipe strapping.

This is an important thing to understand. A ground wire run in a ferrous metal raceway (such as steel EMT) must have the ends of the raceway bonded to the conductor to prevent induction. If you use PVC it's not an issue.

So it's not "bonding their equipment along the way with concrete, metal frame or beams via pipe strapping".

-Hal

 

[RRJ]

This is an important thing to understand. A ground wire run in a ferrous metal raceway (such as steel EMT) must have the ends of the raceway bonded to the conductor to prevent induction. If you use PVC it's not an issue.

So it's not "bonding their equipment along the way with concrete, metal frame or beams via pipe strapping".

-Hal

I know it has to be bonded, what I was saying was that is not as clean as communications people think!


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[LarryFine]

"Are EARTH grounds really necessary for low-noise system operation? Think about all the electronics in an airplane!"

Who needs earth when you're inside a Faraday cage?

 

[paulengr]

Who needs earth when you're inside a Faraday cage?

That’s actually the concept...to avoid ground loops. What most of them fail to realize is that you don’t need to have one ground rod for the building, one for the power system, and one for the AV system. All you really need is to not have ground loops...cross connections where you have a load inducing noise into the audio system.