Parallel equipment grounding conductor

[don_resqcapt19]

Yes. I got that. And I got it that you only are considering the internal grounding conductors as the cable EGC. I'm pretty sure I am clear on what you are advocating. I've been trying to read all of the posts carefully. ...

I am treating it exactly like you treat a metallic conduit with an internal EGC. There is no code rule that requires that you pull an EGC in a metallic raceway, but if you do and if it is in a parallel circuit then it has to be sized based on the circuit OCPD. I don't see why a cable with internal ground wires should be treated any differently.


[/quote]Yes. Got that as well. It follows from the above statement.

My translation is you do not interpret 250.118.10.c as defining the EGC for paralleled MC-HL cables. I got that.

So, give me a grade on how I am doing at paying attention to your position. :happyyes: or :happysad:

ice[/QUOTE]
Yes, you have what I am saying correct.

 

[tkb]

Try a search on "Okonite CLX". I'm sure you will find it. But it will help if you spell "magic: as "MC-HL" :happyyes:

ice

So...you can't come up with a link to back up your claim. :happyno:

 

[iceworm]

I am treating it exactly like you treat a metallic conduit with an internal EGC. There is no code rule that requires that you pull an EGC in a metallic raceway, but if you do and if it is in a parallel circuit then it has to be sized based on the circuit OCPD. I don't see why a cable with internal ground wires should be treated any differently. ...

Yes. Got all that. And, generally all true. I agree there is little difference in the science. As I see it, the difference is a legal code issue.

If I had to guess the code panel's intent on the two (cables and raceways) being different for this issue, it would be that:

1. One can choose the EGC in a raceway - but not so easily in a cable and,

2. There are no safety issues with using the combined sheath and internal egc conductorsof MC-HL, so why not allow a perfectly good cable to be used.

3. I have a design issue with bare EGCs in conduit that is exascerbated by the parallel conductors. Parallel conductors deliver power to a conductor fault from both ends. This is not a problem with the insulated internal egcs in an MC-HL cable. But this is not a code issue - so the panel is likely not responding to that one.
​

ice

 

[don_resqcapt19]

Yes. Got all that. And, generally all true. I agree there is little difference in the science. As I see it, the difference is a legal code issue.

If I had to guess the code panel's intent on the two (cables and raceways) being different for this issue, it would be that:

1. One can choose the EGC in a raceway - but not so easily in a cable and,​

The original rule for the full sized EGC in parallel circuits only applied to conduit. The code was changed to make it apply to both conduits and cables. The fact that it is easier to increase the size of the EGC for conduits and not for cables should not play any part in the making of a code rule. Either you need the "oversized" EGC or you don't need it.

2. There are no safety issues with using the combined sheath and internal egc conductorsof MC-HL, so why not allow a perfectly good cable to be used.

There are no safety issues in using the metal raceway with an EGC sized based on the ampacity of the conductors in the raceway either, but the code says you can't do that. Why should it be different for cables. The physics of the issue are the same, no matter what you enclose the circuit conductors with.

3. I have a design issue with bare EGCs in conduit that is exascerbated by the parallel conductors. Parallel conductors deliver power to a conductor fault from both ends. This is not a problem with the insulated internal egcs in an MC-HL cable. But this is not a code issue - so the panel is likely not responding to that one.

ice

I don't understand the issue that a bare EGC in a raceway would cause.

 

[don_resqcapt19]

The PDF that Ken was talking about clearly shows that the aluminum sheath would be a suitable EGC, but I don't see anything in the code that would let you use the "standard" sized EGCs that are within the cable in a parallel circuit. If there is an EGC of the wire type in the parallel circuit, then it is my opinion, that the code requires that EGC of the wire type to be sized based on the OCPD that is feeding the parallel conductors. I see nothing that would lead me to believe that this rule does not apply to cables.

 

[iceworm]

So...you can't come up with a link to back up your claim. :happyno:

I'm confused. My claim of what? I can think of mayber three that are being discussed.

1. That certain types of MC cable can use the sheath in parallel with the internal grounding conductors for the parallel conductor 250.122.F required EGC?

2. That Okonite CLX meets the criteria of 250.118.10.c?

3. That the egc calculated, meeting the criteria of 250.118.10.c, is suitable for satisfying 250.122.F​

If it is one of these, you're going to have to read the thread - all of it. If, after you have done that, and still can't find the data, post another comment and I'll send you a link to some of the data (the product data sheet)

however, last time I looked the CLX Cable Handbook was only available from Okonite engineering. That's where I got my copy. I won't look for a link for that. If you want one you will have to go after it.

Another reference you will need is UL1569. I've got a subscription. I don't know where you will find it.

The Worm

 

[don_resqcapt19]

Prior to the 93 code the "full size" EGC rule only applied to parallel conductors in raceways. The panel statement on the proposal to make this rule also apply to parallel cable installations said.

It is the Panel's intent that there is no basis for different requirements for parallel equipment grounding conductors in raceways or in cables.

There were no comments in the TCD (now know as the ROC) on this proposed change.

5-217- (250-95): Accept
SUBMrITF~ Dan Leaf, Paso Robles, CA
RECOMMENDATION: Add: "or cables" after "multiple raceways" in the second paragraph, and add: "or cable" after raceway" in the fourth paragraph.
SUBSTANTIATION: Sections 250-79(d) and 310-4 indicate parallel conductors are permitted in cables.
PANEL ACTION: Accept
PANEL STATEMENT. It is the Panel's intent that there is no basis for different requirements for parallel equipment grounding
conductors in raceways or in cables.
VOTE ON PANEL ACTION: Unanimously Affirmative.

 

[iceworm]

Prior to the 93 code the "full size" EGC rule only applied to parallel conductors in raceways. The panel statement on the proposal to make this rule also apply to parallel cable installations said.

There were no comments in the TCD (now know as the ROC) on this proposed change.

So, you maintain that there is no difference between cables and raceways (as far as code issues concerning internal EGCs)

Well, here is a similar question:

Most of the mc-hl comes with 3 paralleled, internal, insulated grounding conductors. That would never be allowed in RMC. Do you wish to never use MC-HL for that reason? In your words, if it is unsafe in RMC then it is unsafe in MC. If you wish to be consistent, you should be arguing to ban any MC cable with segragated grounding conductors.

Or, more probable, the panel didn't mean that cables and raceways should be treated equal in all respects. Since you brought it up, let's look at NEC 1996. .

1996 250.95 is where the "or cable(s) was added. Thei section is the "size of equipment grounding conductors". This section references 1996 250.91.b, types of equipment grounding conductors:

The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:

...
(8) The metalic sheath or combined metalic sheath and grounding conductors of type MC cable.​

Regardless of the what was in the TDC, what made it into the code sounds pretty clear to me. In 1996 the Code allowed the use of the combined sheath and internal egcs. And the section on paralleled conductors referenced that.

Fast forward to 2011: 2011 250.122.F specifies the size of the equipment grounding conductor. 2011 250.118.10.c specifies what can constitute an egc. And the combined sheath and internal grounding conductors are specified as a equipment grounding conductor for certain types of MC cable.

Paraphreased:
You say there is no science or physics that says cable should be treated different than conduit. And I mostly agree, and remind you that regardless, the code does treat them differently.

You say there are no documents that say it is okay for paralleled MC cables to use the combined sheath and internal egcs. And I say 250.118.10.c specifies what constitutes an ecg. And, the NEC is permissive - Show me a document that says you can't.

This has been repeated unto near nausea times. Saying it more often or louder makes neither side more true. It's time to move on.

Here's my suggestion: One more apiece (on this subject anyway, plenty of others this could morph into.) - with something different from the above two. I'll keep mine short.

ice

 

[iceworm]

---

So...you can't come up with a link to back up your claim. :happyno:

tkb -
Let me rephrase my response:
If you want to jump in - have at it. All I ask is for you read the thread - all of the posts.

You generally have pretty good posts - on point and on-target. With all due respect, this one left me pretty cold.

ice

 

[iceworm]

The PDF that Ken was talking about clearly shows that the aluminum sheath would be a suitable EGC, but I don't see anything in the code that would let you use the "standard" sized EGCs that are within the cable in a parallel circuit. If there is an EGC of the wire type in the parallel circuit, then it is my opinion, that the code requires that EGC of the wire type to be sized based on the OCPD that is feeding the parallel conductors. I see nothing that would lead me to believe that this rule does not apply to cables.

Ken -
You must have sent the file to Don. Thank you. He sure wasn't going to believe me. And I was not going to take time to find a link.

ice

 

[iceworm]

3. I have a design issue with bare EGCs in conduit that is exascerbated by the parallel conductors.

... I don't understand the issue that a bare EGC in a raceway would cause.

My current thinking is under fault conditions, a bare internal egc will arc to the conduit. For paralleled installations, the issue is worsened because a fault in the conduit is fed from both sides. My current specification is an insulated internal grounding conductor.

How does one get faults in the conduit? They fill with water, freeze. Insulation crushes, but that is not usually take them out. When the water freezes, it literally pulls the wires in two. Then they fault and if it is a fat circuit, it really makes a mess. One can pull on the conductors from each end until they break off, lay the conductors out on the ground and tell exactly where to dig.

If it is a bare grounding conductor, my perception is the bare conductor is stuck all along the inside of the conduit and is nearly impossible to pull out

But please another day for this one.

ice

 

[iceworm]

You should really take two just to even things up. One to answer post 68. Although, it really isn't my place to tell you how many or what subject. So I won't.

Here is my last on this subject (unless you have something new):

...I don't see anything in the code that would let you use the "standard" sized EGCs that are within the cable in a parallel circuit. If there is an EGC of the wire type in the parallel circuit, then it is my opinion, that the code requires that EGC of the wire type to be sized based on the OCPD that is feeding the parallel conductors. I see nothing that would lead me to believe that this rule does not apply to cables.

Well, I have one trump (and even this is a repeat):

For the last 15 years multiple AHJs have agreed with my interpretation. I don't see them changing their minds now. They would really look :?

ice

 

[don_resqcapt19]

The fact that many AHJs don't enforce the code as it is written does nothing to change my mind on this issue

 

[kenaslan]

There is no link I said earlier that anyone wanting a copy of the pdf send me their email. The Mike Holt site has an upload file size limit and the pdf is 329K

Ken -
You must have sent the file to Don. Thank you. He sure wasn't going to believe me. And I was not going to take time to find a link.

ice

 

[kenaslan]

One last comment, on this thread. The use of the sheath as an EGC is only allowed if the cable connector is approved for grounding. Example, if the use of Roxtec is used, you will then need to use a seperate full size EGC. However most large projects will not allow the use of the sheath as a ground and require two seperate grounds.

The reason some cables come with three grounds, is for VFD drives. These cables will also be shielded and may even come with a GC (ground check) wire.