I have installed isolated ground circuits before and know that there are essentially two grounds, one for the equipment (ground terminal) and the other for the grounding of the outlet and yoke assembly. I am currently bidding a job where the AHJ allows for romex to be installed in a commercial application as long as it is stick built construction. This will be a doctor's office. If I am using romex do I pull a 12/3 w/ground as opposeed to a 12/2 and can I loop them out if they would like the option of moving the same piece of equipment from one side of the room to the other?
isolated grounding
- Thread starter ScottB.
- Start date
- Status
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: isolated grounding
Unfortunately, the regular equipment ground conductor can be either bare or green. The isolated ground equipment ground conductor must be insulated and green.
I don't think NM cable will work in this situation.
See 250.146(D) and 250.119 of the 2002 NEC
[ February 20, 2006, 09:47 PM: Message edited by: ron ]
Unfortunately, the regular equipment ground conductor can be either bare or green. The isolated ground equipment ground conductor must be insulated and green.
I don't think NM cable will work in this situation.
See 250.146(D) and 250.119 of the 2002 NEC
[ February 20, 2006, 09:47 PM: Message edited by: ron ]
- Location
- Illinois
- Occupation
- retired electrician
Re: isolated grounding
Don't plan on using the NM for the exam room. Look at 517.13.
Don
Don't plan on using the NM for the exam room. Look at 517.13.
Don
- Location
- Massachusetts
Re: isolated grounding
Scott in my opinion you have two options.
Option one.
12/2 IG MC cable, that is MC with two green grounding conductors one of which has a yellow strip. The green with yellow is generally used as the IG.
Option 2
Use Hospital grade AC cable, that has an armor that can be used as the equipment ground and the green conductor can be used for the IG.
You do not want a 'bare' IG as then it will not be isolated from contacting other grounded items.
As Don mentioned there are special requirements for the exam room wiring which will likely cause you to buy hospital grade AC for those outlets.
Bob
Scott in my opinion you have two options.
Option one.
12/2 IG MC cable, that is MC with two green grounding conductors one of which has a yellow strip. The green with yellow is generally used as the IG.
Option 2
Use Hospital grade AC cable, that has an armor that can be used as the equipment ground and the green conductor can be used for the IG.
You do not want a 'bare' IG as then it will not be isolated from contacting other grounded items.
As Don mentioned there are special requirements for the exam room wiring which will likely cause you to buy hospital grade AC for those outlets.
Bob
bphgravity
Senior Member
- Location
- Florida
Re: isolated grounding
Southwire makes an "All Purpose HCF MC Cable" that is also suitable for use in health care facilities.
Southwire makes an "All Purpose HCF MC Cable" that is also suitable for use in health care facilities.
Re: isolated grounding
What equipment in a doctors office would need an isolated ground?
Being that the facility is "stick" built (assuming wood construction)) and you are allowed to use a nonmetalic wiring method, your EGC is already isolated, especially if you are running a dedicated circuit 12/2 w G is all that would be needed.
Are you actually looking for a redundant ground path as others have touched on, if so you will have to use a metallic wiring method where the raceway or sheath itself qualifies as an EGC per 250.118.
Roger
What equipment in a doctors office would need an isolated ground?
Being that the facility is "stick" built (assuming wood construction)) and you are allowed to use a nonmetalic wiring method, your EGC is already isolated, especially if you are running a dedicated circuit 12/2 w G is all that would be needed.
Are you actually looking for a redundant ground path as others have touched on, if so you will have to use a metallic wiring method where the raceway or sheath itself qualifies as an EGC per 250.118.
Roger
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Re: isolated grounding
Roger is correct, that the EGC in NM cable, with non-metallic boxes, is as isolated as it gets; the yoke ground might be able to be used as is (floating) if you use non-metallic plates and screws.
Unless someone points out that I did something wrong, for non-NM work, I'd suggest what I'm doing for a job now: use 12/3 MC, strip the entire exposed red conductor for use as the general EGC, and use the insulated green as the IG conductor.
Roger is correct, that the EGC in NM cable, with non-metallic boxes, is as isolated as it gets; the yoke ground might be able to be used as is (floating) if you use non-metallic plates and screws.
Unless someone points out that I did something wrong, for non-NM work, I'd suggest what I'm doing for a job now: use 12/3 MC, strip the entire exposed red conductor for use as the general EGC, and use the insulated green as the IG conductor.
- Status