TYPE MC CABLE

[magoo1960]

WHAT IS THE CORRECT WAY TO USE THE GROUND WIRE THAT IS IN MC CABLE. I normally splice and tail the ground wire so that I can both ground the device as well as attach the ground wire to the metal box. If I am running a IG circuit I use a cable with two grounds. Maybe someone has the answer as well as code sections as I get different answers from everyone.

 

[roger]

Re: TYPE MC CABLE

Originally posted by magoo1960:
WHAT IS THE CORRECT WAY TO USE THE GROUND WIRE THAT IS IN MC CABLE.

You would use it the same as any EGC.

Are you thinking about the runner in the sheath of AC?

Roger

 

[magoo1960]

Re: TYPE MC CABLE

no. I am not thinking of the runner. This topic comes up often but I have yet to have anyone show me in the code book that my install is wrong. I think that by tailing off the ground wire in the mc cable and then terminating it to both the metal box and the device I am fufilling all requirements of the code.

 

[mdshunk]

Re: TYPE MC CABLE

Some skin the ECG mid span to go around the box screw, and then terminate the end to the device. Some have a tail from the box, a tail from the device, and the MC cable's ECG all 3 connected with a B cap or crimp sleeve. One is just as correct as the other. It comes down to your personal preference or the employer's rules and standards.

 

[roger]

Re: TYPE MC CABLE

Originally posted by magoo1960:
no. I am not thinking of the runner. This topic comes up often but I have yet to have anyone show me in the code book that my install is wrong. I think that by tailing off the ground wire in the mc cable and then terminating it to both the metal box and the device I am fufilling all requirements of the code.

Why would this come up often? Your method is the same as many do with an EGC in any conduit or cable installation.

There is an argument that the EGC must have at least 6" free conductor length before landing or connecting to any screw or terminal, this can be easily achieved by pig-tailing as in you are doing.

Roger

 

[magoo1960]

Re: TYPE MC CABLE

THE REASON THIS COMES UP OFTEN IS THAT MANY THINK THAT BECAUSE THE NEC STATES THAT THE METAL SHEATH OF MC CABLE CAN NOT BE CONSIDERED A GROUND UNTO ITSELF. THEY SEEM TO THINK THAT THE GROUND WIRE IN MC IS ONLY TO TAKE THE PLACE OF THE INTERNAL BONDING STRIP OF TYPE AC CABLE. i HAVE HAD MANY TALKS ON JOBSITES ABOUT THIS SUBJECT.

 

[celtic]

Re: TYPE MC CABLE

MC = Romex on steroids

 

[roger]

Re: TYPE MC CABLE

MAGOO, ARE YOU IN A BAD MOOD? UNWAD YOUR PANTIES!!!

The many you hang out with are wrong, hopefully this make you feel better so you can get some peacefull shut eye tonight.


IS THAT CLEAR?

Roger

 

[infinity]

Re: TYPE MC CABLE

Your method is correct. The green insulated condcutor within the MC cable must terminate to the metal box. Also it must be connected to the receptacle unless the receptacle is a self-grounding type. Look at these sections:

250.146 Connecting Receptacle Grounding Terminal to Box.
An equipment bonding jumper shall be used to connect the grounding terminal of a grounding-type receptacle to a grounded box unless grounded as in 250.146(A) through (D).
(A) Surface Mounted Box. Where the box is mounted on the surface, direct metal-to-metal contact between the device yoke and the box or a contact yoke or device that complies with 250.146(B) shall be permitted to ground the receptacle to the box. At least one of the insulating washers shall be removed from receptacles that do not have a contact yoke or device that complies with 250.146(B) to ensure direct metal-to-metal contact. This provision shall not apply to cover-mounted receptacles unless the box and cover combination are listed as providing satisfactory ground continuity between the box and the receptacle.
(B) Contact Devices or Yokes. Contact devices or yokes designed and listed as self-grounding shall be permitted in conjunction with the supporting screws to establish the grounding circuit between the device yoke and flush-type boxes.

250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes.
Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box, any equipment grounding conductor(s) associated with those circuit conductors shall be spliced or joined within the box or to the box with devices suitable for the use in accordance with 250.148(A) through (E).
Exception: The equipment grounding conductor permitted in 250.146(D) shall not be required to be connected to the other equipment grounding conductors or to the box.
(A) Connections. Connections and splices shall be made in accordance with 110.14(B) except that insulation shall not be required.
(B) Grounding Continuity. The arrangement of grounding connections shall be such that the disconnection or the removal of a receptacle, luminaire (fixture), or other device fed from the box does not interfere with or interrupt the grounding continuity.
(C) Metal Boxes. A connection shall be made between the one or more equipment grounding conductors and a metal box by means of a grounding screw that shall be used for no other purpose or a listed grounding device.

 

[macmikeman]

Re: TYPE MC CABLE

When I attended a Western Conference of the IAEI many moons ago they were discussing the new requirement of 6" of free conductor at devices that was about to get put into the code. What I recall from that was the fact that the big concern was not that there is 6" before hitting the ground screw, but rather there is at least 6" after any anchor to the box (clamps, sheath, gr screw, etc), so that the device could be redily removed from the box while the conductors were left intact around the device terminal screws.

 

[busman]

Re: TYPE MC CABLE

Celtic,

MC has more permitted applications than NM. For instance - outdoors and wet locations. Also, MC cannot be used with plastic boxes since the outer sheath is required to be grounded.

Mark

 

[eprice]

Re: TYPE MC CABLE

Originally posted by busman:
Also, MC cannot be used with plastic boxes since the outer sheath is required to be grounded.

The requirement for MC cable used with nonmetallic boxes is the same as any metal raceway or cable method. The applicable section is 314.3. The use of these wiring methods with nonmetallic boxes is allowed if one of the exceptions is complied with.

 

[busman]

Re: TYPE MC CABLE

eprice,

You are correct. What I should have said is that MC is different from NM in that although the outer sheath cannot be used as an EGC, it does have to be grounded. For the record, I have never seen an MC cable connector with a grounding attachment or an MC cable attached to a non-metallic box, but it probably is done.

Thanks for the correction.

Mark