What is an acceptable EGC?

[Barjack]

I don't know if this should be in Grounding vs Bonding or here, but here goes...

I've always been taught, when using conduit of any kind, there should always be and EGC sized according to T.250.122. Where I am confused, is in 250.118, it lists EMT, RNC among others as acceptable EGC's. Does this mean that I could omit an EGC in said raceways as they themselves are an EGC? I don't understand how one would determine the effective ground fault current path for a length of, say 100' of 3/4" EMT. In order to qualify, would the length have to consist of only the conduit and fittings with no boxes in between? If this example were to have 20A #12 circuits in it, would the EMT be comparable to the #12 EGC that would otherwise be required?

 

[mcclary's electrical]

yes,,,the emt is comparible and acceptable as an EGC.

 

[raider1]

If this example were to have 20A #12 circuits in it, would the EMT be comparable to the #12 EGC that would otherwise be required?

The EMT would be a superior fault current path compared to the #12 conductor.

Chris

 

[Barjack]

Thanks for the responses. I'm having a discussion with one of my superiors regarding this issue. He says there has to be a wire EGC regardless of the raceway's composition (could be a local code, St. Petersburg, FL?). The only problem I see is that the EMT raceway's fault path could be compromised with a loose set screw or locknut or if a metallic box in the middle of the run was replaced with a non metallic box after the fact (a long shot, I know, but it could happen).

Also, how does one determine what a metallic raceway's wire equivalent would be for the EGC? Or is the properly sized metallic raceway simply superior to the required wire EGC?

 

[mcclary's electrical]

As long as the EMT is sized properly for what it is containing,,,,,it will ALWAYS be a better fault path than the properly sized (wire)EGC. Yes,,,loose fittings could hamper this,,,,but that's what maintenance is for.

 

[little george]

I think I read in the OP that you mentioned RNC as a grounding conductor. I hope this was a typo.

 

[Barjack]

I think I read in the OP that you mentioned RNC as a grounding conductor. I hope this was a typo.

Sorry, I meant RMC.

Just out of curiosity, how many of us do omit the wire EGC when using metallic conduit?

Not me........

 

[mcclary's electrical]

In most cases,,,,I omit the ground. Why pull it for nothing?,,,,the EMT or RMC is a superior path,,,,,why have two paths? I don't waste material unless it;s an accident or someone gave me bad info.

 

[resistance]

Sorry, I meant RMC.

Just out of curiosity, how many of us do omit the wire EGC when using metallic conduit?

Not me........

I would "never" not run and egc--regardless. NEC is minimum code requirements.

 

[Barjack]

I would "never" not run and egc--regardless. NEC is minimum code requirements.

Agree completely.

 

[Buck Parrish]

If your running conduit useing caddy clips on bar joices. The conduit will be bonded pretty good. In multiple spots. Like every strap.

 

[Barjack]

Now here's the rest of the story. The installation that brought up this discussion contains patient care areas. The circuits for these areas are fed with EMT to the space above the suspended ceiling, with AC going to the receptacles. Lighting is controlled by an LV system with occupancy sensors and 24V switches. Switch boxes are piped in with 1/2" EMT. Are the requirements of 517.13(A) and (B) such that an insulated EGC is required all the way back to the panel, through the EMT, or do the normal wiring methods take over once out of the patient care area (inside the suspended ceiling)?

 

[Buck Parrish]

Patient care areas must have a redundant grounding conductor.

 

[Barjack]

Patient care areas must have a redundant grounding conductor.

Understood. But does that mean the redundant EGC is only required to be in the patient care area, or once the AC or EMT exits the area (into the suspended ceiling and back to the panel) can the redundant EGC be omitted?

I only ask this because I have seen similar installations with AC in the patient care areas fed with MC from the suspended ceiling.

 

[celtic]

Yes,,,loose fittings could hamper this,,,,but that's what maintenance is for.

:-?:-?

You mean people actually go around tightening set screws YEARS after an installation has been completed...sometimes even breaking open walls and ceilings?

Understood. But does that mean the redundant EGC is only required to be in the patient care area, or once the AC or EMT exits the area (into the suspended ceiling and back to the panel) can the redundant EGC be omitted?

I only ask this because I have seen similar installations with AC in the patient care areas fed with MC from the suspended ceiling.

AC?
How/where are they terminating the redundant ground?

Give 517.13 an eyeballing.

 

[Barjack]

:-?:-?
AC?
How/where are they terminating the redundant ground?

Give 517.13 an eyeballing.

I'm sorry. 12/2 AC with an insulated green EGC and the internal bonding strip. Bonding strip is peeled back and wrapped around the outer jacket, and insulated EGC is bonded to the box with a green ground screw, with a pigtail to the ground screw on the receptacle. Correct?

 

[SPROCKET]

In my experience 75% of the time (MAINTENANCE STAFF) are the ones Loosening screws and removing boxes and not properly reinstalling. For this reason I always spend the extra few bucks on the EGC. It may save a life.

 

[macmikeman]

I will volunteer to run a separate ground conductor thru all runs of emt as soon as the poco's of this country run a separate ground conductor with all their service drops....... We could save some cows lives with that one...

 

[brian john]

). The only problem I see is that the EMT raceway's fault path could be compromised with a loose set screw or locknut or if a metallic box in the middle of the run was replaced with a non metallic box after the fact (a long shot, I know, but it could happen).

And an electrician can leave a splice loose, a wirenut loose, not tighten the bonding screw. You cannot (IMO) negate one method in lieu of another based on poor workmanship. Somewhere out there is an electrician that can screw up the installation of an incandescent light bulb.

Show me a fool proff method and I bet I can find a fool to mess it up.

 

[raider1]

Understood. But does that mean the redundant EGC is only required to be in the patient care area, or once the AC or EMT exits the area (into the suspended ceiling and back to the panel) can the redundant EGC be omitted?

I only ask this because I have seen similar installations with AC in the patient care areas fed with MC from the suspended ceiling.

The entire branch circuit supplying patient care areas must comply with 517.13(A) and (B).

Chris