Bonding both ends of metallic armor sheath GEC

[Jpflex]

NEC code requires that if metal conduit / protective cover is used on the grounding electrode conductor especially whether it is 6 AWG but exposed to physical damage, then the conduit / metal sheathing must be bonded at both ends to the grounding electrode conductor.

Since the armor cable which comes with the solid (another code violation) #6 AWG solid grounding electrode conductor slides within the sheathing armor it is not electrically bonded at both ends to the solid grounding electrode conductor as it is so do inspectors just overlook this or what?

Also would mc type bonding bushings be required at the end of armor sheath cables when entering a cabinet to neutral?

 

[Jpflex]

Also I have not drilled into concrete before to insert lugs to secure and support grounding electrode conductor to concrete. Any tips on this?

 

[infinity]

Cable armor like raceways is required to be bonded to the GEC. Why is #6 cable armor a code violation?

 

[don_resqcapt19]

NEC code requires that if metal conduit / protective cover is used on the grounding electrode conductor especially whether it is 6 AWG but exposed to physical damage, then the conduit / metal sheathing must be bonded at both ends to the grounding electrode conductor.

Since the armor cable which comes with the solid (another code violation) #6 AWG solid grounding electrode conductor slides within the sheathing armor it is not electrically bonded at both ends to the solid grounding electrode conductor as it is so do inspectors just overlook this or what?

Also would mc type bonding bushings be required at the end of armor sheath cables when entering a cabinet to neutral?

250.62 Grounding Electrode Conductor Material.
The grounding electrode conductor shall be of copper, aluminum, copper-clad aluminum, or the items as permitted in 250.68(C). The material selected shall be resistant to any corrosive condition existing at the installation or shall be protected against corrosion. Conductors of the wire type shall be solid or stranded, insulated, covered, or bare.

 

[jaggedben]

In my opinion if the GEC is in any way bonded to the enclosure in the panel end, and the cable armor is connected to the enclosure with a proper fitting, that takes care of bonding that end of the cable armor. However, if anyone disagrees and thinks inspectors are 'overlooking' this, a grounding bushing or bonding wedge on the connector should settle any dispute.

I don't know what an 'mc type bonding bushing' is.

At the electrode end of the cable armor you need the proper fitting that clamps onto the armor to bond it.

 

[augie47]

Bond bushing on the panel end and one of these on the rod end.....

 

[Jpflex]

250.62 Grounding Electrode Conductor Material.
The grounding electrode conductor shall be of copper, aluminum, copper-clad aluminum, or the items as permitted in 250.68(C). The material selected shall be resistant to any corrosive condition existing at the installation or shall be protected against corrosion. Conductors of the wire type shall be solid or stranded, insulated, covered, or bare.

According to my grounding and bonding book which references NEC, a grounding electrode conductor that is solid must not be installed in conduit/ sheath if 6 AWG or larger.

 

[Jpflex]

In my opinion if the GEC is in any way bonded to the enclosure in the panel end, and the cable armor is connected to the enclosure with a proper fitting, that takes care of bonding that end of the cable armor. However, if anyone disagrees and thinks inspectors are 'overlooking' this, a grounding bushing or bonding wedge on the connector should settle any dispute.

I don't know what an 'mc type bonding bushing' is.

At the electrode end of the cable armor you need the proper fitting that clamps onto the armor to bond it.

 

[augie47]

According to my grounding and bonding book which references NEC, a grounding electrode conductor that is solid must not be installed in conduit/ sheath if 6 AWG or larger.

I think you might want to re-read 250.64

 

[infinity]

Cable armor is not a conduit. It is a factory assembly.

 

[jaggedben]

According to my grounding and bonding book which references NEC, a grounding electrode conductor that is solid must not be installed in conduit/ sheath if 6 AWG or larger.

What NEC section does it reference? That just sounds incorrect. There's 310.3(C) but that says 8awg and is not specific to grounding.

Also what infinity said. Cable armor is not a raceway.

 

[Jpflex]

What NEC section does it reference? That just sounds incorrect. There's 310.3(C) but that says 8awg and is not specific to grounding.

Also what infinity said. Cable armor is not a raceway.

Cable armor reminds me of flexible metallic conduit and appearance are similar. I tried scanning through my grounding and bonding book during lunch break but I haven’t located the reference yet.

If I remember correctly, if an GEC is 6 AWG or larger it has to be stranded if inserted in a conduit. However if you say cable armor is not recognized as conduit / raceway then this would apply if EMT or RMC was used as a conduit to protect GEC. I’ll try again to find that passage in the book and send the picture here

 

[jaggedben]

It's not a raceway if you don't pull wires through it. If the wire comes wrapped in it from the factory then it's part of the cable. Like MC cable, for example.

 

[texie]

And just as an FYI for jpflex, I'll point out that the NEC only requires bonding at each end of ferrous metal raceway. For example, if you ran a GEC in aluminum raceway this would not be required, it would just be the same as, say, PVC.
I realize that this does not directly apply to your question for armored GEC as AFAIK all armored GEC is steel. Just thought I would mention it as your original post referred to only metallic.

 

[Jpflex]

And just as an FYI for jpflex, I'll point out that the NEC only requires bonding at each end of ferrous metal raceway. For example, if you ran a GEC in aluminum raceway this would not be required, it would just be the same as, say, PVC.
I realize that this does not directly apply to your question for armored GEC as AFAIK all armored GEC is steel. Just thought I would mention it as your original post referred to only metallic.

So my confusion was obviously how to treat the armor cable factory installed with the grounding electrode conductor, since the conductor moves within the armor - not an electrical tight bond).

Therefore, I was not sure if I had to not only use a listed fitting to clamp down the armor to the GEC into the cabinet for bonding at one end and whether to ensure a fitting did the same (squeeze down the armor onto the GEC at the other end for no conductor movement within armor near the ground rod for proper bonding).

 

[jaggedben]

It isn't about squeezing the GEC. The right fitting bonds the armor to either the enclosure or the GEC. (Frankly this code requirement is probably overkill for cable armor that makes contact with the GEC all along it's length but it's a one size fits all rule that applies to insulated and bare GECs.)

At the panel end you could use a regular MC type connector. At the rod end you need something like this:

https://www.amazon.com/Sigma-Electric-ProConnex-41409-Armored/dp/B000GAV98G/ref=asc_df_B000GAV98G/

Note the extra clamp that bonds the cable armor while the GEC gets the regular bond with screw, so that both are bonded to the clamp and therefore each other.

 

[Jpflex]

It isn't about squeezing the GEC. The right fitting bonds the armor to either the enclosure or the GEC. (Frankly this code requirement is probably overkill for cable armor that makes contact with the GEC all along it's length but it's a one size fits all rule that applies to insulated and bare GECs.)

At the panel end you could use a regular MC type connector. At the rod end you need something like this:

https://www.amazon.com/Sigma-Electric-ProConnex-41409-Armored/dp/B000GAV98G/ref=asc_df_B000GAV98G/

Note the extra clamp that bonds the cable armor while the GEC gets the regular bond with screw, so that both are bonded to the clamp and therefore each other.

Without the proper fitting at the end of the armor and GEC at the end toward the grounding electrode a “one size fits all” armor that allows free movement of the GEC would not allow proper bonding between the armor and GEC. I’ve seen some ground connectors here at our company with only one screw for the GEC and or sheath

So it makes sense to have the proper fitting so both armor and GEC are bonded

 

[jaggedben]

I'm not sure why you're concerned with 'free movement' in particular. But yes, you need proper fittings and if the armor can slide around on the GEC then you almost certainly don't have those fittings.

The code rule is to actually make the conduit carry current with the GEC, in case the GEC is carrying current which they often do. Otherwise the armor or conduit could heat up inductively.

 

[wwhitney]

The code rule is to actually make the conduit carry current with the GEC, in case the GEC is carrying current which they often do. Otherwise the armor or conduit could heat up inductively.

Is it really true that shifting some of the current from the copper wire to the steel armor would reduce the total heating? I.e. that the inductive heating would go down more than the resistive I²R heating? That square exponent makes me wonder, although I don't know what the formula for inductive heating would be and how it would vary with current.

Anyway, my understanding of the reason for bonding both ends is to reduce the high frequency choke effect that would otherwise raise the impedance for lightning events.

Cheers, Wayne

 

[LarryFine]

Anyway, my understanding of the reason for bonding both ends is to reduce the high frequency choke effect that would otherwise raise the impedance for lightning events.

What he ^ said.