Pull an isolated ground?

[Irving LaRue]

My journeyman and I pulled a long run to supply these receptacles. They’re for a set of cubicles that have built-in receptacles. We originally pulled the circuits with 1 ground wire and do not include an isolated ground. We realized our mistake and pulled an isolated ground in later.

Why do we need an isolated ground? I understand isolated grounds are used in situations where sensitive equipment is being used, such as hospitals. However, this is just a couple of cubicals in an office. Nothing more sensitive than a printer or laptop will be plugged in.

It seems unnecessary to me. We pulled it according to the specs because that’s what’s required, but I don’t understand why it’s necessary in this situation. Do you think an isolated ground was necessary here?

 

[roger]

It is unnecessary and is held over from a time where some electronics used the chassis ground for part of the circuit.

As far as hospitals, in patient care areas it's the exact opposite, 517.13 requires redundant grounds, as in multiple EGC's connected in parallel.

 

[Seven-Delta-FortyOne]

Isolated grounds were a thing a while back. They are in fact not permitted in many sections of hospitals, I believe patient rooms and critical care areas, but I’d have to look it up.

At the end of the day though, if it’s on the plans, and you didn’t get it removed through the rfi process, you install it, whether you feel it’s necessary or not.

 

[infinity]

It seems unnecessary to me. We pulled it according to the specs because that’s what’s required, but I don’t understand why it’s necessary in this situation. Do you think an isolated ground was necessary here?

No they're not necessary and are pretty much obsolete and a waste of money for cubicles.

 

[ActionDave]

The extra green wasn't necessary just because the diagram that comes with the office furniture shows it, it has to be part of the specs in the approved plans before you would be required to install it.

 

[infinity]

And pulling the IG is only half of the puzzle. You would then need to install the proper IG receptacles which means that the vendor would actually have to supply them.

 

[ron]

And pulling the IG is only half of the puzzle. You would then need to install the proper IG receptacles which means that the vendor would actually have to supply them.

The 3rd half is what did he do with the IG on the source end of the circuit? It is unlikely it was run isolated to the X0 of the upstream separately derived source.

 

[Irving LaRue]

The 3rd half is what did he do with the IG on the source end of the circuit? It is unlikely it was run isolated to the X0 of the upstream separately derived source.

It was run to the ground bar on the sub panel which feeds the circuit.

 

[Irving LaRue]

And pulling the IG is only half of the puzzle. You would then need to install the proper IG receptacles which means that the vendor would actually have to supply them.

I don’t remember the receptacle looking any different than all the others.

 

[infinity]

It was run to the ground bar on the sub panel which feeds the circuit.

What was the ground bar connected to? If it was isolated and run correctly that's how it is normally done.

 

[ron]

What was the ground bar connected to? If it was isolated and run correctly that's how it is normally done.

99% of the time, the subpanel has a bonded ground bar and the isolated ground conductor terminated onto it becomes useless for its intended purpose.

 

[rambojoe]

It was run to the ground bar on the sub panel which feeds the circuit.

Yeah...thats not isolated...
What is the voltage in the buildings Main?

In other words.. if the y/g iso is on the same buss as the e.g.c.- with one equipment ground incoming w/ the feeders... its not iso.

 

[hbiss]

That furniture is so old that I'm surprised it didn't have knob and tube wiring. Seriously, you have to keep in mind the vintage of any instructions like that. We don't do it like that anymore.

-Hal

 

[noonan]

Date code shows 05/24.

 

[tom baker]

I don’t remember the receptacle looking any different than all the others.

IG would have an orange triangle, the device can be any color

 

[infinity]

Date code shows 05/24.

Yup, pretty standard wiring diagram (3+1 or 2+2) for modern office partitions. For 4 circuit systems the receptacles are typically labeled A,B,C, and D.

 

[LarryFine]

3+1 or 2+2

For a 3ph or a 1ph supply, respectively.

 

[infinity]

For a 3ph or a 1ph supply, respectively.

The 2+2 can be from either system.

 

[LarryFine]

The 2+2 can be from either system.

True, but still wired as 1ph.

 

[hbiss]

Date code shows 05/24.

Yeah. Boiler plate from 05/1974. It even says you have the option to do the grounds however you want. If that tag is all you are going by and not a spec from an engineer, just know that we don't do iso grounds anymore.

-Hal