Isolated Ground Conductor

[justin59]

I have been taught by the owner of my old company that 1 isolated ground conducter is required per isolated ground circuit. I was just in a debate about this today and im starting to think that I was taught wrong. I cannot find anything in the code that supports this. Any thoughts?

 

[jeremysterling]

Read 250.146(D).

It is permissible to run the EGC as your old boss taught you, but not required.

 

[iwire]

I have been taught by the owner of my old company that 1 isolated ground conducter is required per isolated ground circuit.

How far back would he have you go?

 

[justin59]

How far back would he have you go?[/QUOTE]

He's been in the trade for around 30 years or so if that helps. I talked to him tonight and I found out his practice of installing it this way is based off of hear say. He was excited to find out that he could just run one iso conducter per raceway as it saves greatly on cost.

 

[don_resqcapt19]

Any time I did an install where the specs called for an isolated ground, they always called for each circuit to have its own isolated grounding conductor and neutral. This is not a code rule, but was only a project specification.

 

[iMuse97]

I'm following Don's train of thought. If the specs call for an isolated ground, the isolation must continue back to the source of the branch circuit. Would it even be called an isolated ground otherwise? I don't think so.

 

[infinity]

I'm following Don's train of thought. If the specs call for an isolated ground, the isolation must continue back to the source of the branch circuit. Would it even be called an isolated ground otherwise? I don't think so.

I would agree with you if the branch circuit originates at the service. Otherwise it should continue back to the service bonding point of the neutral and bonding jumper or to the XO of a transformer.

 

[Pierre C Belarge]

If isolated receptacles share an isolated ground conductor, how is that isolated ground conductor isolated?

 

[chris kennedy]

If isolated receptacles share an isolated ground conductor, how is that isolated ground conductor isolated?

Wow, try saying that 3 times fast. Is that from Dr. Seuss?

 

[Pierre C Belarge]

Wow, try saying that 3 times fast. Is that from Dr. Seuss?

One of my favorites.

Can you imagine if he was an electrician???:grin:

 

[iwire]

If isolated receptacles share an isolated ground conductor, how is that isolated ground conductor isolated?

I would hate to run 42 - 12 AWGs all the way back to XO.

All IGs share conductors in my experience:smile:

 

[LarryFine]

If isolated receptacles share an isolated ground conductor, how is that isolated ground conductor isolated?

It's good if all of the IG receptacles on one circuit share a single IG. It's just basically run like an additional circuit conductor.

 

[dereckbc]

If you really want to do it right, just install an isolation transformer to establish a new ground reference free of any common mode noise.

 

[justin59]

It's good if all of the IG receptacles on one circuit share a single IG. It's just basically run like an additional circuit conductor.

This is exactly how i have been taught and this is how i have done it since day one. But now that i have actually looked it up for myself, i find nothing in the nec to require this method.

 

[infinity]

This is exactly how i have been taught and this is how i have done it since day one. But now that i have actually looked it up for myself, i find nothing in the nec to require this method.

You're right, you won't find any NEC requirements for using IG's at all. You can use one properly sized IG for all 42 circuits in a panel if you so choose, one per circuit or something in between. This is a design issue not a code issue. IMO IG's in general are a waste of money and one IG per circuit is an even bigger waste of money.