This is not how you do isolated ground ....

[ggunn]

If you are interpreting the word " isolated " as not being conducted. just stick the ground out side the panel and let it hang in free air! Then it would surely be isolated.

The confusion is in the what the installer defines as "isolated" .

If you have an isolated grounding receptacle you attach it to the isolated screw on the receptacle and don't attach it to anything all the way back to main panel ground.

That would be isolated but it wouldn't be a ground.

I understand how this stuff works. The confusion comes from the idea that there can be two grounds which are absolutely isolated from each other.

 

[Daniel malack]

That would be isolated but it wouldn't be a ground.

I understand how this stuff works. The confusion comes from the idea that there can be two grounds which are absolutely isolated from each other.

It's real simple. It's isolated for what is going on in the branch circuits. If you isolate the ground at main , other faults won't effect this isolated ground ckt. I believe all isolated ckts are dedicated. You can't isolate it by driving a separate ground rod, uffer, bldg steel, ground ring etc.. you would never get the breaker to trip by running a separate electrode.

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[ggunn]

deleted

 

[Smart $]

... You can't isolate it by driving a separate ground rod, uffer, bldg steel, ground ring etc..

It is also a violation of 250.50. :happyyes:

 

[Daniel malack]

It is also a violation of 250.50. :happyyes:

Correct. Using a definition of isolated to the extreme would be let it hang outside the panel in free air. Correct isolation is all the way back to the main. If a fault to ground occurs anywhere in the building it won't effect this isolated ckt. Electrons won't back up and go away from source and effect isolated equipment. If you ground every single conduit, box, and fixture. then if a fault to ground occurs it will take path of least resistance, if through sensitive equipment, it will. That is isolated Ground! It is isolated from other effects on the electrical system.

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[victor.cherkashi]

Correct. Using a definition of isolated to the extreme would be let it hang outside the panel in free air. Correct isolation is all the way back to the main. If a fault to ground occurs anywhere in the building it won't effect this isolated ckt. Electrons won't back up and go away from source and effect isolated equipment. If you ground every single conduit, box, and fixture. then if a fault to ground occurs it will take path of least resistance, if through sensitive equipment, it will. That is isolated Ground! It is isolated from other effects on the electrical system.

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in my opinion, the "extreme" solution is to install transformer and connect to it all equipment required IG grounding.

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[hbiss]

Well no. The ground(s) and the secondary side grounded conductor still have to be connected to the the service. You can't have an isolation transformer with the secondary floating.

There are isolation transformers that are designed to supply "technical power" that have a center tapped secondary. 60-0-60. But the center tap has to be connected to the service ground.

-Hal

 

[Andy Delle]

What cracks me up are the few contractors and consumer boards that install isolated ground circuits in residential for computers and more complex AV systems!

Think about it...

The box (metal or plastic) is attached to a wooden stud. The cable is no doubt Romex and this is always a dedicated circuit. So even a straight installation is in fact the same electrically as an isolated ground in this case. If a cheap receptacle bothers you then just use a spec grade. No need for IG.

 

[Sparky Adam]

Why not use a transformer to truly isolate those circuits? Or just ignore it and tell them it's isolated and they would never know.

 

[Fulthrotl]

Why not use a transformer to truly isolate those circuits? Or just ignore it and tell them it's isolated and they would never know.

truly isolated outlets (as in a CCCU at a hospital) have no ground
whatsoever. just two wires from the outlet, to the secondary side
of the transformer. the only way you can get shocked is by getting
across both of those.

critical cardiac care patients are touchy about shocks. even static electricity
is a potentially lethal thing to them.

however, electrical engineers can decide amazing things. one of them did
not like all the 500 mcm's cadwelded on a ground bus, cause some of them
came down from above, and some came up from below. bus was in ceiling.
above T bar. he wanted them all to come down from above, to prevent "ground loops."

i'm not making this chit up.

 

[mbrooke]

truly isolated outlets (as in a CCCU at a hospital) have no ground
whatsoever. just two wires from the outlet, to the secondary side
of the transformer. the only way you can get shocked is by getting
across both of those.

critical cardiac care patients are touchy about shocks. even static electricity
is a potentially lethal thing to them.

however, electrical engineers can decide amazing things. one of them did
not like all the 500 mcm's cadwelded on a ground bus, cause some of them
came down from above, and some came up from below. bus was in ceiling.
above T bar. he wanted them all to come down from above, to prevent "ground loops."

i'm not making this chit up.

That would be a code violation- they need an EGC even if no terminal of the secondary is grounded down.

 

[MAC702]

What ever happened to balancing the load in that panel 1 phase has almost all load.

We don't know the actual connected loads. It could very well be as balanced as they could make it if the 2-pole load is significant and the six 1-pole loads aren't.