MC connector

SAP

Senior Member
I always used MC connectors to connect my armored ground. I used the snap in MC connector. AHJ said it was not properly bonded with that connector, this job was a service change for a solar array, Solar Company drove a ground rod by there disconnect on the other side of house and used a Romex connector with a ground bushing to bond there armored ground and that was properly bonding the MC according to the inspector, I have used Romex connectors on MC but never if the inspector can see it and only has a last resort, My GEC is water then to ground rod #4 it's about a 50 foot run. Does anybody know of a way I can bond the mc
 

jumper

Senior Member
If your snap in connector was a listed MC connecter then:

Solar guy is nuts and inspector is wrong.
 

SAP

Senior Member
I'm 99 percent it's a listed MC connecter the only thing I'm concerned about is the connector is for dry location but so is MC, I'm going to the parts house this morning I will get the exact part number for the mc connector, The job is 2 hrs away that's four hrs of driving.
 

iwire

Moderator
Staff member
What code section requires any connector to be used with armored or bare GECs?
 

jumper

Senior Member
I'm 99 percent it's a listed MC connecter the only thing I'm concerned about is the connector is for dry location but so is MC, I'm going to the parts house this morning I will get the exact part number for the mc connector, The job is 2 hrs away that's four hrs of driving.
Unless you have the coated/jacketed MC, your MC is not rated for a wet location. Your standard MC connector will not be either.
 

jumper

Senior Member
My armored jacket of my GEC needs to be bonded on both ends
Getting confused here.

Do you have a piece of MC cable or a GEC in flexible metal conduit? Or a piece of MC as a GEC?:?

A GEC in a metallic raceway would require bonding on both ends.
 

GoldDigger

Moderator
Staff member
Getting confused here.

Do you have a piece of MC cable or a GEC in flexible metal conduit? Or a piece of MC as a GEC?:?

A GEC in a metallic raceway would require bonding on both ends.
A ferrous metal raceway would require bonding because of the choke effect.
(Note to self: Do not put a ferrite choke on the GEC to reduce ground noise either! :angel:)
 

SAP

Senior Member
Sorry bout the confusion it is metallic cable with with 1 # 6 solid copper wire, I talked to Arlington, they said not only is there MC box connectors, But any manufacturers MC connectors have to be UL listed for 514.B tested for bonding and grounding thanks for the input
 

hbiss

EC, Westchester, New York NEC: 2014
Sorry bout the confusion it is metallic cable with with 1 # 6 solid copper wire...
I am going with none of the above.

I am betting the OP has bare armored copper GEC cable.

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet261

It is not FMC, MC or NM, none of those connector types will likely be listed for bare armored ground. It is very small diameter.
I agree.

... I talked to Arlington, they said not only is there MC box connectors, But any manufacturers MC connectors have to be UL listed for 514.B tested for bonding and grounding thanks for the input
Thing is what you are using is not MC so what Arlington said is not applicable. I also do not agree that the armor on bare armored cable even needs to be bonded. Whatever the case I can't see an MC connector closing tight enough on that small diameter to provide a reliable connection. You usually see Romex connectors used even though they are not listed for it either because they will at least tighten on the cable.

-Hal
 

al hildenbrand

Senior Member
Armored ground wire is in the UL White Book as KDER (it is not Armored Cable, a different classification)

2015 - 16 UL Guide Information For Electric Equipment -- The White Book

GROUNDING AND BONDING EQUIPMENT (KDER)
USE
This category covers bonding devices, ground clamps, grounding and bonding bushings and locknuts, ground rods, armored grounding wire, protector grounding wire, grounding wedges, ground clips for securing the ground wire to an outlet box, water-meter shunts, and similar equipment.

Some devices are to be assembled to wire using a special tool specified by the manufacturer. Such special tooling is identified by appropriate marking on or within the device shipping carton.

Armored Grounding Wire — Armored grounding wire consisting of a single corrosion-resistant copper, aluminum or copper-clad aluminum conductor within helically-formed steel armor is marked with the size of the conductor ‘‘Bare Armored Grounding Wire.’’

Ground Rods — Ground rods and pipe electrodes . . .
 
I also do not agree that the armor on bare armored cable even needs to be bonded.

-Hal
Don't believe in the choke effect? Remember ferrous metal -- not aluminum or copper -- is used as core for transformers. Steel metal concentrates the magnetic field (generated by the current in the GEC) and Lenz's law says the increasing magnetic flux will try to oppose the change by slowing down the current in GEC -- we call this a choking effect.
 

tkb

Senior Member
Don't believe in the choke effect? Remember ferrous metal -- not aluminum or copper -- is used as core for transformers. Steel metal concentrates the magnetic field (generated by the current in the GEC) and Lenz's law says the increasing magnetic flux will try to oppose the change by slowing down the current in GEC -- we call this a choking effect.
Isnt the armor touching the bare conductor for the full length?
Doesn't this have an affect on the choke?
 

al hildenbrand

Senior Member
Don't believe in the choke effect? Remember ferrous metal -- not aluminum or copper -- is used as core for transformers. Steel metal concentrates the magnetic field (generated by the current in the GEC) and Lenz's law says the increasing magnetic flux will try to oppose the change by slowing down the current in GEC -- we call this a choking effect.
You state the theoretical basis of the choke effect well enough.

However, we are looking at a product designed to carry an unbalanced time-varying current of significant magnitude adequate to trip service overcurrent protective devices and adequate to carry lightning to ground.

Can you point to documentation about the back-EMF choking this non-Article 320, non-Article 330 armored grounding wire?
 
“However, we are looking at a product designed to carry an unbalanced time-varying current of significant magnitude adequate to trip service overcurrent protective devices and adequate to carry lightning to ground.

Can you point to documentation about the back-EMF choking this non-Article 320, non-Article 330 armored grounding wire?”

Are you asking why the Armor Grounding Wire -- a specific designed product for working as GEC – needs additional bonding at both ends? Obviously if such product already meets the code, that it is already having the conduit bonded at both ends to the inside copper conductor, then it should meet the code. But in practice I would think many cases people buy a 30 ft armor wire and only use a fraction of the length for the job, meaning they cut the cable to length, which means the cut end needs to be bonded.

Here is a good article to explain the choking effect: http://www.ecmag.com/section/codes-standards/guardian-ground

“The magnetic field’s strength increases in proportion to the amount of current in the conductor. In many cases, the magnetic lines of force in the conductor are induced into the conduit enclosing the grounding electrode conductor; they can even surpass the saturation point of the steel raceway. At the point where the grounding electrode conductor exits the conduit, the magnetic lines of force generated by the fault current in the conductor will try to be induced on the end of the conduit, creating a saturation point that exceeds the conduit’s capacity. The steel conduit, in this instance, acts like a steel core of a coil to concentrate the magnetic lines of force. This condition is often referred to as the “choke effect” because it is actually the restriction of a grounding electrode conductor from performing its function. Because of this, specific bonding requirements are necessary for ferrous metal raceways that contain grounding electrode conductors. This is not a concern for grounding electrode conductors that are installed in PVC conduit or other nonferrous metal raceways such as aluminum or brass conduit.”

Lenz’s Law is a perfect tool to explain all of this, and not just for designing electric motors or generators.

Also someone asked why the ferrous metal conduit carrying a bare copper conductor inside – touching each other already – that still required to be bonded together at both ends? Touching together and measured at zero Ohms does not guarantee to have low impedance at lightning high current at frequencies of mega or giga Herzts. Think about why bonding meta raceway to enclosure using lock nut on concentric knockout is not allowed, even though it is measured with perfect zero Ohm?
 
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