517.13 NEC Handbook 'Explanation'

[brentp]

The NEC Handbook explanation following 517.13(B)states; "The requirements in 517.13(B) cover the second component of the redundant grounding approach. An insulated, copper, equipment grounding conductor sized in accordance with 250.122 must be installed with the branch-circuit conductors in the wiring method that meets the provisions of 517.13(A). The conductor can be either solid or stranded. It is not required to run a separate, insulated equipment grounding conductor to the branch-circuit panelboard where the feeder wiring method is recognized as an equipment grounding conductor per 250.18, or the feeder wiring method contains an equipment grounding conductor".


I am questioning whether or not this explanation is correct as there is not a section 250.18, and that there is no exception not requiring an EGC in 517.13(B). What am I missing here?

Thanks in advance for your comments.

 

[websparky]

Re: 517.13 NEC Handbook 'Explanation'

Mis-print!

Try 250.118

Here are the exceptions:

Exception No. 1: Metal faceplates shall be permitted to be grounded by means of a metal mounting screw(s) securing the faceplate to a grounded outlet box or grounded wiring device.

Exception No. 2: Luminaires (light fixtures) more than 2.3 m (71/2 ft) above the floor and switches located outside of the patient vicinity shall not be required to be grounded by an insulated equipment grounding conductor.

[ April 06, 2004, 06:59 PM: Message edited by: websparky ]

 

[brentp]

Re: 517.13 NEC Handbook 'Explanation'

250.118, should have caught that .

It is not required to run a separate, insulated equipment grounding conductor to the branch-circuit panelboard where the feeder wiring method is recognized as an equipment grounding conductor per 250.18, or the feeder wiring method contains an equipment grounding conductor".

Why is this only in the Handbook and not included in 517.13(B) exceptions?

 

[roger]

Re: 517.13 NEC Handbook 'Explanation'

First of all, the handbook commentary is only opinions and is not actual code.

Forget the handbook commentary and stick with the pure wording of 517.13(B) specifically "operating over 100 volts, shall be grounded by an insulated copper conductor."

Also, take note of the insulated bonding conductor in 517.14.


This wording

. It is not required to run a separate, insulated equipment grounding conductor to the branch-circuit panelboard where the feeder wiring method is recognized as an equipment grounding conductor per 250.18, or the feeder wiring method contains an equipment grounding conductor".

is probably meant for 517.19(D)

Roger

[ April 06, 2004, 07:35 PM: Message edited by: roger ]

 

[brentp]

Re: 517.13 NEC Handbook 'Explanation'

517.19(D) was next

Why isn't "It is not required to run a separate, insulated equipment grounding conductor to the branch-circuit panelboard where the feeder wiring method is recognized as an equipment grounding conductor per '250.118', or the feeder wiring method contains an equipment grounding conductor" included in 517.19(D)? Why do I have to comply with 517.19(D)(1)(2)&(3) if "the feeder wiring method contains an equipment grounding conductor" properly bonded to the branch circuit panel?

517 should be 'crystal clear' with so much importance being given to grounding/bonding.

p.s.- I hope I'm not coming on too strong on my first posts as I have learned alot from this forum and am not really trying to 'criticize' the Code.

 

[roger]

Re: 517.13 NEC Handbook 'Explanation'

Brent,

Why do I have to comply with 517.19(D)(1)(2)&(3) if "the feeder wiring method contains an equipment grounding conductor" properly bonded to the branch circuit panel?

because it's the code.

If you have a reason as to why the wording of the "Handbook" should be code, submit an ROP for the 2008 cycle.

PS, I agree that this may be an over site, although the metallic raceway should still be bonded as worded regardless.

Roger

 

[brentp]

Re: 517.13 NEC Handbook 'Explanation'

I hear what you're saying Roger and appreciate your responses.

 

[roger]

Re: 517.13 NEC Handbook 'Explanation'

Welcome to the forum Brent.

Roger

 

[steve66]

Re: 517.13 NEC Handbook 'Explanation'

Brent:

Notice 517.19(D) falls under 517.19 which only applies to "critical care areas". Your hospital or facility (or their engineers) have the responsibility of deciding which areas are critical care. Notice you only have to use one of the three in 517.19(D). The intent is to make sure the raceway serves its purpose as an equipment ground return path.

Steve

 

[brentp]

Re: 517.13 NEC Handbook 'Explanation'

Steve,

I'm with you on the Code rules, and my install will follow the rules.

I guess my real question is 'why'.

Why doesn't 517.19(D) give relief if a copper egc is installed with the feeder conductors? Why is the 'extra' bonding required on the feeder raceway and not the branch?

I hope I'm not beating this subject to death.

 

[caj1962]

Re: 517.13 NEC Handbook 'Explanation'

The "why" is because in critical care ares if a patient is not able to defend(JCAHO wording) himself from a shock hazard or tell his care giver he is feeling a tingle then we must do everything we can to guard against this. By adding the redundant grounding system through the raceway and also with an insilated grounding conductor we now have the "best" of and maybe the fastest way to clear any fault current that the paient or care giver might feel.
Just my humble thoughts with over 10 years in a health care setting

 

[steve66]

Re: 517.13 NEC Handbook 'Explanation'

Brent:

I understand your confusion, and to be honest, I never realized before that an EGC is not required with the feeder. (Actually, you have it backwards in your last post. The "extra" bonding is required on the branch circuits, not on the feeder.) Even though it is not required, I always specify an EGC to be ran with the feeders.

To be sure we are all on the same page, here is how I understand the rules (put simply):

1. The raceway has to be a ground path for both branch circuits and feeders. No exceptions.

2. Branch circuits in patient care areas require an additional grounding conductor.

3. Critical care areas require raceway connections that ensure the raceway remains a ground path.

The code makes it quite clear that a grounding wire can't substitute for a raceway ground. I'm not exactly sure why, but I could take some guesses at it. As CAJ implied, somehow the raceway ground must have some advantage over a EGC.

Steve

 

[brentp]

Re: 517.13 NEC Handbook 'Explanation'

Steve,

The 'extra bonding' I'm talking about is 517.19(D) concerning feeder raceways - bonding bushings, threaded bosses, bonding locknuts...a copper egc is ignored. These rules do not apply to the branch raceways. If the metal raceway is so important as an egc, why not apply 517.19(D) to branch raceways? Feeders and branch raceways have different rules and I don't know why.

If we're going to give the "best" system possible to critical care areas, then let's do it. No requirement for a copper egc installed with the feeder conductors baffles me.

Also seems to me that 517.19(D) would make underground pvc raceways for the emergency system a violation.

 

[roger]

Re: 517.13 NEC Handbook 'Explanation'

Hello Brent,

Also seems to me that 517.19(D) would make underground pvc raceways for the emergency system a violation.

actualy 517.30(C)(3) does that.

Roger

 

[brentp]

Re: 517.13 NEC Handbook 'Explanation'

Hello Roger,

I can't count the number of installations that have underground pvc raceways from the gensets to transfer switches. No metal raceway, so the copper egc is sufficient, and the underground burial depth/concrete cover is sufficient for mechanical protection.

An emergency generator serves patient & critical care areas.

Brent

 

[iwire]

Re: 517.13 NEC Handbook 'Explanation'

Not that Roger needs any help but I am bored.

517.30 Essential Electrical Systems for Hospitals.

(C) Wiring Requirements.

(3) Mechanical Protection of the Emergency System. The wiring of the emergency system of a hospital shall be mechanically protected by installation in nonflexible metal raceways, or shall be wired with Type MI cable.

I do not see PVC listed as an option

 

[brentp]

Re: 517.13 NEC Handbook 'Explanation'

Originally posted by iwire:
Not that Roger needs any help but I am bored.

517.30 Essential Electrical Systems for Hospitals.

(C) Wiring Requirements.

(3) Mechanical Protection of the Emergency System. The wiring of the emergency system of a hospital shall be mechanically protected by installation in nonflexible metal raceways, or shall be wired with Type MI cable.

I do not see PVC listed as an option

I'm sorry you're bored with this iwire, and I know Roger needs no help in dealing with me.
I have the utmost respect for the people on this forum, that's why I'm here.

I do know that many engineers and jurisdictions have no problem with underground pvc installations for the emergency systems. Do I see a conflict? Yes. That's why I brought it up.

 

[iwire]

Re: 517.13 NEC Handbook 'Explanation'

Originally posted by brentp:
I'm sorry you're bored with this iwire,

You misunderstood my statement, I did not mean I was bored with this thread, or your post, just bored watching TV so I thought I would post the article in question.

Sorry if the meaning of my comment was not clear.

Originally posted by brentp:
I do know that many engineers and jurisdictions have no problem with underground pvc installations for the emergency systems.

I think you might want to say something like "in the area I work"

I know the company I work for would never take the gamble of running underground PVC conduits for this when it is clearly a violation of the NEC.

We might if the AHJ put it in writing that they have no problem with PVC for this. ( I do not see that happening )

Bob

[ April 09, 2004, 04:25 AM: Message edited by: iwire ]

 

[brentp]

Re: 517.13 NEC Handbook 'Explanation'

Sorry I misunderstood you iwire. I know you have more class than that.

 

[steve66]

Re: 517.13 NEC Handbook 'Explanation'

brent:

(Actually, you have it backwards in your last post. The "extra" bonding is required on the branch circuits, not on the feeder.)

Sorry my mistake. I see what you are saying now. My best guess that the "extra" grounding in 517.19(D) is required because an EGC isn't required with the feeder. Should there be an exception to (D) if a EGC is included with the feeder? Again, I assume since this exception doesn't exist, somehow the raceway ground must be better than a EGC. Personally, I agree with your comment about requireing the "best" system with a raceway ground and an EGC both in feeder and branch circuits.

As to the PVC conduit: I think 517.19(D) does NOT prohibit PVC conduits. 517.19(D) says

 WHERE...a metal feeder raceway or Type MC or MI cable is installed

So the extra grounding is only required IF you install metal conduit. (....more confusion)