Code reference

Status
Not open for further replies.
drbond24

drbond24

Senior Member
Location
Barboursville, West Virginia
Could someone give me the code reference that says it is OK to use multiple smaller grounds instead of a single larger one? I have tray cable with segmented grounds and want to make sure that the 3 smaller grounds are allowed to be used instead of a single normal sized ground.

Thanks.
 
I don't think you'll find one. The code gives a size, and does not have a provision for adding small cables to make an equal to a larger one. This isn't like achieving a total ampacity by paralleling conductors of lesser ampacity. The code does not have us select EGC size in terms of ampacity. With a given OCPD, you use a given EGC. That's all there is.

This causes a problem, from time to time, when MC cable is used. If you have to upsize the phase conductor of an MC cable, due to voltage drop, there is no way to also upsize the EGC.
 
My boss told me that it was OK to substitute smaller conductors as long as the total cross sectional area was greater than or equal to the requirement (i.e. 3-#14 AWG instead of a single #10 AWG).

If there isn't a code reference to permit this, can I still do it as long as there isn't a reference prohibiting it?

Edit: I did not intend that to sound snippy, but it looks like it might have come out that way. The problem here is that the cable exists and I'm trying to prove it is OK, but my boss' word is not law, so I need to prove it with the NEC one way or the other, if that is possible.
 
It causes a problem regularly with MC cable. Most all MC cables use segmented grounding conductors.

For example Okonite MC-HL 3C - 350 uses 3 -#7 adding to a #3 for the grounding conductor.

I've had one case where the AHJ questioned the termination of all three under one lug since the lug was not listed for three conductors. The electricians had chucked the three in a drill and twisted them up clean and tight, trimmed and terminated under the ground lug.

So far no one has said, "Hey, the code says you got to have a #4, you can't use 3 - #7."

Check UL.1569, Construction and Testing of MC cable. The grounding conductor is permitted to be sectioned. Other commonly used terms describing the sectioned grounding conductor are ?partitioned? and ?interstitial?.

carl
 
drbond24 said:
Could someone give me the code reference that says it is OK to use multiple smaller grounds instead of a single larger one? I have tray cable with segmented grounds and want to make sure that the 3 smaller grounds are allowed to be used instead of a single normal sized ground.Thanks.
Click to expand...
And
drbond24 said:
I found that section 10.1.6(a) of UL 1277 allows it, and there doesn't seem to be anywhere in the NEC that disallows it...
Click to expand...

I?m not sure what ?segmented grounds? means maybe parallel? If you mean ground (earthing) then your electrode rod is sized at 250-52(A)(5) and it?s conductor at 250-66.

I got a feeling your talking about equipment grounding conductor (EGC) and that is qualified in 250-118 and sized as per 250-122.

Notice 250-119(B) Multiconductor Cable, ?Where conditions of maintenance and supervision ensure that only qualified persons service the installation, one or more?shall be permitted to be permanently identified as equipment grounding conductor?
But this is really stretching what you may be looking for and is not the intent:roll:

If your looking for NEC to qualify parallel EGC?s your application must follow 250-122(F) your application does not qualify in this light.
 
250.4 A 5 - egc shall be capable of carrying the maximum current likely to be imposed. I don't see where there is an exception to this. Am I missing something ?
 
drbond24 said:
I found that section 10.1.6(a) of UL 1277 allows it, and there doesn't seem to be anywhere in the NEC that disallows it...

I think I'm covered. Thanks for the help!
Click to expand...


YES. IT'S ALLOWED BECAUSE I'M IN THE NAVY AND WE USE MULTIPLE GROUNDS ALL THE TIME. IT'S IN OUR CABLE FOR INSTALLING GENERATORS TO MILITARY PANEL BOXES.

BIGSID,
MASTER ELE. VA.
 
Bigsid, try to avoid using all caps, it makes your post hard to read and is perceived as shouting.

There's something that's said quite a bit around here, "I've been doing it for years and never failed an inspection for it." That does not necessarily indicate code compliance. From what I've heard, military installations tend to go uninspected as well, so that is something I consider in reading your response as well.
 
Status
Not open for further replies.
Top