250.64(E)(1)

[shawnbebout]

So I was looking at my 2014 Handbook, sizing the grounding electrode conductor. I noticed that 250.64(E)(1) requires the grounding electrode conductor and the ferrous metal raceway and enclosures to be bonded at each end of the raceway. I didn't know it was both ends, I just thought it was one end......

 

[don_resqcapt19]

So I was looking at my 2014 Handbook, sizing the grounding electrode conductor. I noticed that 250.64(E)(1) requires the grounding electrode conductor and the ferrous metal raceway and enclosures to be bonded at each end of the raceway. I didn't know it was both ends, I just thought it was one end......

That is one of the few places where the conduit must be bonded at both ends. There is some disagreement as to what type of bonding is required at the enclosure. Also this bonding rule requires that the bonding jumper be the same size as the GEC.

 

[MasterTheNEC]

Seems fairly clear to me - "Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or groundingelectrode conductor."

 

[FionaZuppa]

Seems fairly clear to me - "Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or groundingelectrode conductor."

isnt a metal raceway the egc when terminated by metal-metal contact ??

why does it say Ferrous?

CAUTION: The effectiveness of the grounding electrode can be significantly reduced if a ferromagnetic raceway containing a grounding electrode conductor isn't bonded to the grounding electrode conductor at both ends. This is because a single conductor carrying high-frequency lightning current in a ferrous raceway causes the raceway to act as an inductor, which severely limits (chokes) the current flow through the grounding electrode conductor. ANSI/IEEE 142, Recommended Practice for Grounding of Industrial and Commercial Power Systems (Green Book) states, a€œAn inductive choke can reduce the current flow by 97 percent.a€

Author's Comment: To save a lot of time and effort, simply run the grounding electrode conductor exposed if not subject to physical damage [250.64(B)], or enclose it in a nonmetallic conduit that is suitable for the application.

 

[shawnbebout]

I just think it would be a good burrito bet. You know most guys don't bond the GEC at both ends. Tell them they are wrong, and get them to bet a breakfast burrito. Then break out the above mention code. BOOM, free burrito.

 

[shawnbebout]

Also this bonding rule requires that the bonding jumper be the same size as the GEC.

I don't see anywhere in 250.64(E)(1) that says anything about sizing the GEC.

 

[augie47]

I don't see anywhere in 250.64(E)(1) that says anything about sizing the GEC.

That's because 250.64(E) does not address sizing the conductor other than to say the bonding jumper to bond the raceway itself needs to be the same size as the grounding electrode conductor.

250.66 addresses the size of the conductor itself.

 

[MasterTheNEC]

isnt a metal raceway the egc when terminated by metal-metal contact ??

why does it say Ferrous?

Well now....you did say EGC (Equipment Grounding Conductor) I fear......and we are talking about the GEC (Grounding Electrode Conductor)...Right.

 

[don_resqcapt19]

I don't see anywhere in 250.64(E)(1) that says anything about sizing the GEC.

250.64(E) does not say anything about the sizing of the GEC itself, but it does tell you how to size the bonding jumper between the GEC and the ferrous metal raceway. 250.64(E)(3).

 

[don_resqcapt19]

Seems fairly clear to me - "Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or groundingelectrode conductor."

It does not specify the type of bonding that is required at the metallic enclosure. Two lock nuts will meet the definition of bonded, but that is often not acceptable to the the inspector.

 

[MasterTheNEC]

It does not specify the type of bonding that is required at the metallic enclosure. Two lock nuts will meet the definition of bonded, but that is often not acceptable to the the inspector.

I hear ya Don.

However, I make it simple.....I bond one end of the GEC to one end of the ferrous raceway and on the other end I place a bonding bushing and loop the 6 AWG through the lay in lug, on the bushing and then continue up to the grounded conductor terminal bus....no need to make it an argument with the inspector over intent, lose more time wrestling in the mud over a 3-5 dollar bushing. (maybe higher....I don't actually break a sweet anymore as many will remind you.

I do see it many times where the connection at the ROD end is done....and not at the enclosure end, as you have stated. It all brings me back to this statement " Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor.

But I do conceded that I have seen it done both ways. I am just a believer in it says what it says....do what it says.

HOWEVER. I do happen to believe the reason I did it that way in the past was simply to avoid an argument. Clearly in the SOARES BOOK it shows it without that direct connection at the panel enclosure. I agree with that but why have the argument. I mean lets be honest, if the raceway is connected to the cabinet, the GEC is ultimately connected to the bus that is bonded to the cabinet and ultimately the enclosure is bonded to both so the old way I did it was overkill but then again the inspectors in my area (years ago) did not know any better.

 

[augie47]

It does not specify the type of bonding that is required at the metallic enclosure. Two lock nuts will meet the definition of bonded, but that is often not acceptable to the the inspector.

I guess I'm one of "those" . I only have a draft of the '14 but the wording there is: "Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor"as MastertheNEC pointed out. I don't see how bonding the raceway by any means accomplishes that. In earlier versions there was mention of "raceways not physically continuous" which opened the door to some consideration IMO, but the '14, if worded like my Draft Copy seems to requires bonding to the conductor. That is, of course, just my opinion.

 

[MasterTheNEC]

I guess I'm one of "those" . I only have a draft of the '14 but the wording there is: "Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor"as MastertheNEC pointed out. I don't see how bonding the raceway by any means accomplishes that. In earlier versions there was mention of "raceways not physically continuous" which opened the door to some consideration IMO, but the '14, if worded like my Draft Copy seems to requires bonding to the conductor. That is, of course, just my opinion.

Yeah see thats the real problem with that language. You are 100% right on the change from the 2011 NEC to the 2014 NEC as many things were added. Here is the difference in the two....and as I said prior to this I always did it the bonding bushing way....to avoid confusion....it the 2014 edition it was changed slightly.

2011 NEC - (E) Enclosures for Grounding Electrode Conductors.
Ferrous metal enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Nonferrous metal enclosures shall not be required to be electrically continuous. Ferrous metal enclosures that are not physically continuous from cabinets or equipment to the grounding electrode shall be made electrically continuous by bonding each end of the raceway or enclosure to the
grounding electrode conductor. Bonding methods in compliance with 250.92(B) for installations at service equipment locations and with 250.92(B)(2) through (B)(4) for other than
service equipment locations shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode. The
bonding jumper for a grounding electrode conductor raceway or cable armor shall be the same size as, or larger than, the enclosed grounding electrode conductor. If a raceway is used
as protection for a grounding electrode conductor, the installation shall comply with the requirements of the appropriate raceway article.

2014 NEC (1) General. Ferrous metal raceways and enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor. Nonferrous metal raceways and enclosures shall not be required to be electrically continuous.

(2) Methods. Bonding shall be in compliance with 250.92(B) and ensured by one of the methods in 250.92(B)(2) through (B)(4).

this was to kinda see how both flow. Just can't get past that last line....to the grounding electrode or grounding electrode conductor

 

[MasterTheNEC]

So I took the liberty of looking up the history on this and with some guidance from the Hartwell Handbook. I do not like the wording in 2014 BUT I believe it to be that once the raceway (ferrous) is bonded to the enclosure (properly) and when I say properly, I do not think a "standard lock-nut" will do but a bonding locknut or bushing would do. The reason for that is that in the 2014 NEC, in 250.64(E)(2) says :

(2) Methods. Bonding shall be in compliance with 250.92(B) and ensured by one of the methods in 250.92(B)(2) through (B)(4).

when we look at those sections it is clear what we are trying to achieve at the enclosure with the raceway. "Bonding jumpers meeting the requirements of this article shall be used around
impaired connections, such as reducing washers or oversized, concentric, or eccentric knockouts. Standard locknuts or bushings shall not be the only means for the bonding required by this section but shall be permitted to be installed to make a mechanical connection of the raceway(s)."

and of course I like option (B)(4) (i'm bias) -(4) Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers

So with that said.....2011 NEC and earlier a bit murky......2014 NEC I think I might just use bonding locknuts with PERFECT KO's or punched KO's and if concentric or eccentric, which is probably the case I will stick with the bonding bushings and avoid the arguments.

 

[MasterTheNEC]

So I took the liberty of looking up the history on this and with some guidance from the Hartwell Handbook. I do not like the wording in 2014 BUT I believe it to be that once the raceway (ferrous) is bonded to the enclosure (properly) and when I say properly, I do not think a "standard lock-nut" will do but a bonding locknut or bushing would do. The reason for that is that in the 2014 NEC, in 250.64(E)(2) says :

(2) Methods. Bonding shall be in compliance with 250.92(B) and ensured by one of the methods in 250.92(B)(2) through (B)(4).

when we look at those sections it is clear what we are trying to achieve at the enclosure with the raceway. "Bonding jumpers meeting the requirements of this article shall be used around
impaired connections, such as reducing washers or oversized, concentric, or eccentric knockouts. Standard locknuts or bushings shall not be the only means for the bonding required by this section but shall be permitted to be installed to make a mechanical connection of the raceway(s)."

and of course I like option (B)(4) (i'm bias) -(4) Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers

So with that said.....2011 NEC and earlier a bit murky......2014 NEC I think I might just use bonding locknuts with PERFECT KO's or punched KO's and if concentric or eccentric, which is probably the case I will stick with the bonding bushings and avoid the arguments.

 

[GoldDigger]

isnt a metal raceway the egc when terminated by metal-metal contact ??

why does it say Ferrous?

It says ferrous because the conduit section around the GEC is also a ferrous metal core with one turn of the GEC running through it. That makes it an inductor (choke) which drastically increases the impedance of that section of the GEC at high frequencies (lightning induced, for example).
Bonding at both ends allows the current to flow through the raceway itself instead, which does not couple magnetically to itself.
Not the same thing as skin effect.

 

[infinity]

So I took the liberty of looking up the history on this and with some guidance from the Hartwell Handbook. I do not like the wording in 2014 BUT I believe it to be that once the raceway (ferrous) is bonded to the enclosure (properly) and when I say properly, I do not think a "standard lock-nut" will do but a bonding locknut or bushing would do. The reason for that is that in the 2014 NEC, in 250.64(E)(2) says :

(2) Methods. Bonding shall be in compliance with 250.92(B) and ensured by one of the methods in 250.92(B)(2) through (B)(4).

when we look at those sections it is clear what we are trying to achieve at the enclosure with the raceway. "Bonding jumpers meeting the requirements of this article shall be used around
impaired connections, such as reducing washers or oversized, concentric, or eccentric knockouts. Standard locknuts or bushings shall not be the only means for the bonding required by this section but shall be permitted to be installed to make a mechanical connection of the raceway(s)."

and of course I like option (B)(4) (i'm bias) -(4) Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers

So with that said.....2011 NEC and earlier a bit murky......2014 NEC I think I might just use bonding locknuts with PERFECT KO's or punched KO's and if concentric or eccentric, which is probably the case I will stick with the bonding bushings and avoid the arguments.

I agree, if you use a bonding locknut on the raceway that's attached to the enclosure which is connected to the GEC you have satisfied the requirement. Trying to wrap a #3/0 copper conductor around an 1.25" bonding bushing is silly. :slaphead:

 

[MasterTheNEC]

I agree, if you use a bonding locknut on the raceway that's attached to the enclosure which is connected to the GEC you have satisfied the requirement. Trying to wrap a #3/0 copper conductor around an 1.25" bonding bushing is silly. :slaphead:

Well that's because you used a 3/0 CU on a ground rod....not my problem

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[infinity]

Well that's because you used a 3/0 CU on a ground rod....not my problem

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Maybe the other end was to the water pipe.

 

[MasterTheNEC]

Maybe the other end was to the water pipe.

Nah.....I just use rods....I grew up in Virginia.

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