Isolated Ground Receptacles

[kwired]

I've never gone to that extreme. I use a separate conductor for each circuit, run with the circuit conductors.

How often were you running the circuits to the service equipment vs a panel 11 floors from the service equipment or similar situation?

 

[LarryFine]

How often were you running the circuits to the service equipment vs a panel 11 floors from the service equipment or similar situation?

I understand that the isolated grounding conductor ideally is terminated at the building main bonding point. In most cases, in existing structures, where there already are IG circuits, there already is an IG bus in the panel, which is connected back at the main bond. I land my new IG conductors there.

If I had to run down 11 floors, because there was no such conductor, I would make sure it was possible to add an IG conductor to the feeder pathway, and make sure I was getting paid to do it. M point above was that I have never run a separate IG conductor for each receptacle, just each circuit.

 

[kwired]

I understand that the isolated grounding conductor ideally is terminated at the building main bonding point. In most cases, in existing structures, where there already are IG circuits, there already is an IG bus in the panel, which is connected back at the main bond. I land my new IG conductors there.

If I had to run down 11 floors, because there was no such conductor, I would make sure it was possible to add an IG conductor to the feeder pathway, and make sure I was getting paid to do it. M point above was that I have never run a separate IG conductor for each receptacle, just each circuit.

Many never do, but at same time one must determine what/how much isolation is desired as this is an option that is above/beyond code minimum requirements. Then you have to question how isolated the equipment supplied is if there is other metallic pathways that connect to it anyway:blink:

 

[JoeStillman]

One should open their dry transformers periodically and blow the dust off the coils, this reduces dirty power conditions

:lol:

Note that the spec was for IG to electrified furniture. That means it was specified by someone who probably doesn't know the implications of what they've asked for. If the specs don't say what to isolate the ground from, then just run the extra stripey green wire with the branch circuit conductors and bond it to the panel ground bus. If the system has EGC's with all the feeders (as almost all do nowadays) it will perform exactly as well as something isolated all the way back to the grounding electrode system.

Under no circumstances should it be isolated from the building's grounding electrode system, or run to a "dedicated ground rod" somewhere.

 

[JoeStillman]

I've been in this business 40 years and I have never heard an anecdote or read a story about how someone solved a problem by installing IG outlets, nor isolated EGC's. I used to encounter clients who's point-of-sale equipment vendors required it for their cash registers, but even that is rare now. They are still popular, however, with audio entertainment specialists. Hum in an audio circuit can be a real pain to track down.

 

[dmsv10]

Design choice, unless you have separate panels feeding the computer outlets with a Priority Generator Power or UPS circuit. We had 800+ workstations with three circuits, two normal, one or Computer circuit on a UPS backup, in which case, the IGs went to the third panel fed by UPS only, not back to the mains utility.



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[brantmacga]

Isolated Ground Receptacles

Something else I wanted to point out, is that it may not necessarily be the EE that is specifying the IG, but the equipment vendor, and then the EE adds it to the specs.

Your customer may be leasing their computers from a company that requires it.

We build restaurants for maybe 6-7 different brands; there is one particular POS vendor and a digital sign vendor that absolutely requires IG & TVSS on every install, and other vendors that do not.

We have to send pictures of the IG install before they’ll come on-site, and sign an affidavit at completion that the install was done per their specs.

Some years ago we had to go into several older locations that did not have IG and add it to the system when the client was upgrading their terminals. It’s also not uncommon for me to find an egregiously wrong IG install during remodels. The most common is where another contractor installs an IG grounding bar and then connects that to a single electrode outside the building, not bonded to the grounding system. Another favorite of mine is seeing grounding bars lifted from the can using a block of wood, and then running screws through the ground bar and the wood into the can.

I tend to not argue with whether or not it works, and just appreciate the extra work they give us.


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[dmsv10]

I've been in this business 40 years and I have never heard an anecdote or read a story about how someone solved a problem by installing IG outlets, nor isolated EGC's. I used to encounter clients who's point-of-sale equipment vendors required it for their cash registers, but even that is rare now. They are still popular, however, with audio entertainment specialists. Hum in an audio circuit can be a real pain to track down.

Correct, human design error, we had a MDF or IDF closet where the electrical engineer put a 480/120/208vac 300 KVA xfmr adjacent side of this cable distribution closet within 2' where the magnetic flux from the xfmr was inducing voltage into the cabling, thus, even with the shielding on the Cat-6 we ended up with so much noise, it dropped comm for the 300+ users. Human error.

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[hbiss]

IG receptacles are a throwback to the days when communications between computers and peripherals was via RS-232. Unlike ethernet, RS-232 wiring has a common conductor that is grounded to the frame or chassis of each device. Because the line cord grounds are also connected to the same point at each device, there was the real possibility of ground loops since devices can be on different circuits or even different sub-panels. Hence the requirement for bringing all line cord grounds directly back to a common point which is what IG is all about.

Today, there is no need to do this with data and ethernet connected devices but the mindset still persists. As mentioned, analog audio can still benefit though if there are multiple equipment locations with shielded cables connecting them.

-Hal